﻿ ﻿Solar Insolation - Solar Electricity Handbook 2011: A Simple Practical Guide to Solar Energy - Designing and Installing Photovoltaic Solar Electric Systems - Michael Boxwell

# Solar Electricity Handbook 2011: A Simple Practical Guide to Solar Energy - Designing and Installing Photovoltaic Solar Electric Systems - Michael Boxwell (2011)

### Appendix B. Solar Insolation

Solar insolation shows the daily amount of energy from the sun you can expect per square metre at your location, averaged out over the period of a month. The figures are presented as an average irradiance, measured in kilowatt-hours per square metre spread over the period of a day (kWh/m²/day).

Averages have been collated over a 22-year period between 1983 and 2005, based on a three-hour sample rate.

The book only shows solar insolation figures for the United States, Canada, Australia, New Zealand, UK and Ireland. Whilst I have tried to show this information as clearly as possible, the information is in tabular form which does not display well on some smaller eBook readers. More detailed information can be accessed at www.SolarElectricityHandbook.com, with figures for every major town and city in every country in the world, thereby allowing you to access information that is specific to your area.

Understanding this information

The amount of energy you capture from the sun differs, depending on the tilt of the solar panels. If you mount your solar panels horizontally or vertically, you will capture less energy than if you face them due south (due north in the Southern Hemisphere) and tilt them towards the sun.

The tables on the following pages show the irradiance figures based on mounting your solar panels at the following angles:

· Flat (horizontal)

· Upright

· Tilted towards the equator for best year-round performance

· Tilted for best performance during the winter months

· Tilted for best performance during the summer months

· Tilted with the angle adjusted each month throughout the year

Where the figures show the panels tilted at a fixed angle, I show this angle in the left hand column as the angle adjustment from an upright (vertical) position. On the bottom row, where the optimum tilt changes each month, I show this angle underneath each month’s irradiance figures. Please note: all angles are in degrees from vertical.

For a more detailed explanation of these figures, refer to the chapter on Calculating Solar Energy.

Solar insolation values - Australia

New South Wales

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 5.91 5.25 4.48 3.56 2.73 2.49 2.68 3.49 4.6 5.41 5.88 6.24 Upright - 0° 2.34 2.56 2.93 3.36 3.43 3.77 3.78 3.83 3.54 2.83 2.40 2.31 56° angle Year-round tilt 5.38 5.11 4.84 4.42 3.87 3.90 4.04 4.68 5.33 5.50 5.43 5.57 40° angle Best winter tilt 4.74 4.66 4.62 4.45 4.07 4.20 4.32 4.82 5.22 5.11 4.82 4.85 72° angle Best summer tilt 5.78 5.32 4.82 4.16 3.46 3.37 3.54 4.28 5.16 5.63 5.80 6.04 Tilt adjusted each month 5.78 72° 5.34 64° 4.84 56° 4.47 48° 4.07 40° 4.27 32° 4.32 40° 4.82 48° 5.33 56° 5.63 64° 5.80 72° 6.24 80°

Northern Territory

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 5.83 5.18 5.07 4.81 4.35 4.24 4.47 5.07 5.98 6.59 6.5 6.27 Upright - 0° 2.43 1.81 2.28 3.09 3.73 4.24 4.23 3.75 2.99 2.02 2.32 2.79 73° angle Year-round tilt 5.85 5.04 5.13 5.15 4.94 4.99 5.20 5.62 6.23 6.48 6.48 6.36 57° angle Best winter tilt 5.58 4.68 4.94 5.21 5.23 5.43 5.61 5.83 6.13 6.04 6.12 6.13 89° angle Best summer tilt 5.84 5.18 5.08 4.84 4.40 4.29 4.52 5.12 6.00 6.59 6.51 6.28 Tilt adjusted each month 5.84 89° 5.18 81° 5.13 73° 5.22 65° 5.23 57° 5.56 50° 5.61 57° 5.83 65° 6.23 73° 6.60 81° 6.51 89° 6.37 96°

Queensland

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 6.19 5.39 4.95 3.98 3.23 3.02 3.22 4.04 5.12 5.52 6.07 6.35 Upright - 0° 2.09 2.28 2.81 3.22 3.41 3.75 3.76 3.85 3.39 2.49 2.13 2.04 62° angle Year-round tilt 5.65 5.22 5.19 4.61 4.12 4.13 4.29 4.99 5.65 5.50 5.61 5.71 46° angle Best winter tilt 4.98 4.78 4.96 4.63 4.32 4.44 4.57 5.15 5.54 5.11 4.99 4.98 78° angle Best summer tilt 6.06 5.41 5.15 4.34 3.71 3.59 3.78 4.56 5.47 5.62 5.98 6.18 Tilt adjusted each month 6.06 78° 5.42 70° 5.19 62° 4.65 54° 4.32 46° 4.50 38° 4.57 46° 5.15 54° 5.65 62° 5.62 70° 5.98 78° 6.35 86°

South Australia

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 6.81 6.18 4.91 3.75 2.71 2.29 2.53 3.21 4.32 5.34 6.29 6.67 Upright - 0° 2.54 2.94 3.32 3.72 3.54 3.48 3.63 3.52 3.37 2.87 2.54 2.42 55° angle Year-round tilt 6.15 6.05 5.42 4.80 3.94 3.60 3.86 4.29 5.01 5.45 5.80 5.93 39° angle Best winter tilt 5.36 5.49 5.19 4.86 4.15 3.87 4.12 4.41 4.89 5.05 5.12 5.13 71° angle Best summer tilt 6.65 6.31 5.37 4.49 3.51 3.13 3.39 3.95 4.86 5.58 6.21 6.45 Tilt adjusted each month 6.65 71° 6.32 63° 5.42 55° 4.87 47° 4.15 39° 3.93 32° 4.12 39° 4.41 47° 5.01 55° 5.58 63° 6.21 71° 6.68 78°

Victoria

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 6.36 5.83 4.51 3.23 2.23 1.78 1.94 2.59 3.55 4.72 5.74 6.22 Upright - 0° 2.62 3.00 3.24 3.35 3.02 2.77 2.81 2.89 2.85 2.72 2.56 2.49 52° angle Year-round tilt 5.75 5.74 5.04 4.22 3.33 2.87 3.00 3.48 4.10 4.80 5.30 5.53 36° angle Best winter tilt 5.02 5.20 4.81 4.25 3.48 3.06 3.17 3.55 3.98 4.43 4.69 4.79 68° angle Best summer tilt 6.22 6.00 5.01 3.97 3.00 2.52 2.67 3.24 4.02 4.94 5.67 6.01 Tilt adjusted each month 6.22 68° 6.02 60° 5.04 52° 4.27 44° 3.48 36° 3.09 28° 3.17 36° 3.55 44° 4.10 52° 4.94 60° 5.67 68° 6.23 76°

Western Australia

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 8.41 7.49 5.93 4.34 3.09 2.62 2.82 3.62 5.04 6.41 7.71 8.45 Upright - 0° 2.46 3.08 3.76 4.12 3.77 3.68 3.71 3.74 3.74 3.09 2.55 2.3 58° angle Year-round tilt 7.51 7.31 6.53 5.46 4.29 3.89 4.05 4.69 5.80 6.54 7.06 7.39 42° angle Best winter tilt 6.47 6.61 6.28 5.55 4.53 4.18 4.32 4.83 5.69 6.07 6.16 6.28 74° angle Best summer tilt 8.18 7.62 6.43 5.07 3.82 3.37 3.56 4.3 5.59 6.67 7.59 8.14 Tilt adjusted each month 8.18 74° 7.63 66° 6.53 58° 5.56 50° 4.53 42° 4.25 34° 4.32 42° 4.83 50° 5.80 58° 6.67 66° 7.59 74° 8.45 82°

Alberta

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 0.79 1.70 3.15 4.56 5.32 5.66 5.56 4.76 3.14 1.85 0.99 0.48 Upright - 0° 1.58 2.60 3.52 3.63 3.24 3.11 3.19 3.36 3.03 2.51 1.81 0.95 36° angle Year-round tilt 1.61 2.84 4.26 5.00 4.87 4.82 4.89 4.84 3.86 2.84 1.89 0.97 20° angle Best winter tilt 1.66 2.85 4.09 4.55 4.30 4.21 4.30 4.33 3.63 2.80 1.93 1.00 52° angle Best summer tilt 1.47 2.69 4.21 5.20 5.29 5.33 5.39 5.14 3.90 2.74 1.75 0.89 Tilt adjusted each month 1.66 20° 2.86 28° 4.26 36° 5.21 44° 5.29 52° 5.72 60° 5.39 52° 5.20 44° 3.86 36° 2.85 28° 1.93 20° 1.00 12°

British Columbia

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 1.00 1.88 2.9 4.18 5.18 5.7 6.11 5.37 4.00 2.19 1.18 0.84 Upright - 0° 1.52 2.44 2.73 2.93 2.89 2.86 3.15 3.43 3.54 2.62 1.73 1.37 42° angle Year-round tilt 1.63 2.78 3.52 4.34 4.75 4.92 5.42 5.40 4.78 3.09 1.87 1.43 26° angle Best winter tilt 1.67 2.78 3.37 3.97 4.17 4.24 4.69 4.85 4.53 3.06 1.91 1.48 58° angle Best summer tilt 1.51 2.63 3.50 4.52 5.12 5.42 5.91 5.70 4.79 2.96 1.74 1.31 Tilt adjusted each month 1.67 26° 2.80 34° 3.52 42° 4.53 50° 5.12 58° 5.75 66° 5.91 58° 5.74 50° 4.78 42° 3.10 34° 1.91 26° 1.48 18°

Manitoba

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 1.24 2.17 3.43 4.74 5.57 5.84 5.92 5.00 3.45 2.25 1.42 0.99 Upright - 0° 2.15 3.01 3.50 3.48 3.16 3.00 3.15 3.28 3.07 2.81 2.34 1.84 40° angle Year-round tilt 2.24 3.37 4.41 5.08 5.13 5.05 5.27 5.04 4.09 3.26 2.47 1.87 24° angle Best winter tilt 2.31 3.39 4.24 4.65 4.51 4.42 4.57 4.53 3.87 3.24 2.54 1.95 56° angle Best summer tilt 2.04 3.18 4.34 5.26 5.53 5.57 5.74 5.31 4.12 3.12 2.27 1.69 Tilt adjusted each month 2.31 24° 3.41 32° 4.41 40° 5.26 48° 5.53 56° 5.90 64° 5.74 56° 5.36 48° 4.09 40° 3.27 32° 2.54 24° 1.95 16°

New Brunswick

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 1.61 2.46 3.68 4.46 4.91 5.45 5.25 4.78 3.75 2.45 1.53 1.28 Upright - 0° 2.53 3.11 3.45 3.03 2.64 2.64 2.66 2.90 3.10 2.81 2.19 2.06 45° angle Year-round tilt 2.67 3.59 4.52 4.69 4.56 4.75 4.68 4.73 4.32 3.37 2.39 2.15 29° angle Best winter tilt 2.77 3.61 4.37 4.30 4.03 4.11 4.09 4.27 4.1 3.35 2.45 2.24 61° angle Best summer tilt 2.43 3.37 4.45 4.84 4.90 5.21 5.08 4.98 4.34 3.22 2.20 1.95 Tilt adjusted each month 2.77 29° 3.62 37° 4.52 45° 4.85 53° 4.90 61° 5.48 68° 5.08 61° 5.02 53° 4.32 45° 3.38 37° 2.45 29° 2.24 22°

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 1.23 2.07 3.27 4.16 4.75 5.16 4.90 4.36 3.25 2.09 1.26 0.99 Upright - 0° 1.91 2.68 3.12 2.87 2.64 2.62 2.59 2.73 2.72 2.43 1.83 1.63 43° angle Year-round tilt 2.03 3.06 4.03 4.30 4.34 4.48 4.35 4.29 3.73 2.89 1.99 1.7 27° angle Best winter tilt 2.09 3.07 3.88 3.94 3.83 3.88 3.80 3.87 3.53 2.86 2.03 1.77 59° angle Best summer tilt 1.87 2.89 3.99 4.47 4.68 4.93 4.74 4.53 3.77 2.77 1.85 1.55 Tilt adjusted each month 2.09 27° 3.08 35° 4.03 43° 4.48 51° 4.68 59° 5.20 66° 4.74 59° 4.58 51° 3.73 43° 2.90 35° 2.03 27° 1.77 20°

Nova Scotia

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 1.54 2.39 3.47 4.29 4.98 5.57 5.49 4.85 3.91 2.66 1.57 1.21 Upright - 0° 2.85 3.27 3.34 2.84 2.59 2.59 2.66 2.87 3.28 3.23 2.49 2.25 45° angle Year-round tilt 2.89 3.70 4.39 4.45 4.62 4.85 4.90 4.82 4.62 3.82 2.64 2.27 29° angle Best winter tilt 3.06 3.77 4.26 4.09 4.07 4.18 4.26 4.34 4.40 3.84 2.74 2.4 61° angle Best summer tilt 2.56 3.42 4.28 4.61 4.96 5.31 5.32 5.06 4.60 3.60 2.39 2.01 Tilt adjusted each month 3.06 29° 3.78 37° 4.39 45° 4.61 53° 4.96 61° 5.60 68° 5.32 61° 5.10 53° 4.62 45° 3.86 37° 2.74 29° 2.42 22°

Ontario

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 1.53 2.35 3.29 4.35 5.12 5.88 5.87 5.02 3.92 2.64 1.55 1.24 Upright - 0° 2.63 3.04 3.02 2.83 2.61 2.64 2.74 2.91 3.21 3.07 2.29 2.21 46° angle Year-round tilt 2.71 3.50 4.04 4.50 4.75 5.12 5.24 4.98 4.58 3.68 2.47 2.24 30° angle Best winter tilt 2.85 3.55 3.91 4.13 4.19 4.41 4.55 4.49 4.36 3.69 2.56 2.37 62° angle Best summer tilt 2.41 3.25 3.96 4.65 5.10 5.6 5.69 5.23 4.56 3.48 2.25 1.99 Tilt adjusted each month 2.85 30° 3.56 38° 4.04 46° 4.66 54° 5.10 62° 5.90 70° 5.69 62° 5.27 54° 4.58 46° 3.71 38° 2.56 30° 2.39 22°

Prince Edward Island

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 1.35 2.10 3.22 4.28 5.40 6.05 6.04 5.22 3.91 2.34 1.29 0.98 Upright - 0° 2.09 2.63 2.98 2.9 2.89 2.88 3.00 3.20 3.30 2.70 1.81 1.51 44° angle Year-round tilt 2.21 3.04 3.90 4.42 5.01 5.23 5.37 5.20 4.57 3.23 1.98 1.6 28° angle Best winter tilt 2.29 3.05 3.75 4.05 4.40 4.50 4.65 4.68 4.33 3.20 2.02 1.65 60° angle Best summer tilt 2.03 2.87 3.87 4.59 5.40 5.75 5.85 5.48 4.58 3.09 1.84 1.47 Tilt adjusted each month 2.29 28° 3.06 36° 3.90 44° 4.60 52° 5.40 60° 6.09 68° 5.85 60° 5.52 52° 4.57 44° 3.24 36° 2.02 28° 1.65 20°

Quebec

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 1.51 2.44 3.60 4.51 4.97 5.48 5.21 4.70 3.49 2.15 1.40 1.18 Upright - 0° 2.42 3.16 3.44 3.10 2.71 2.7 2.69 2.91 2.91 2.47 2.03 1.97 43° angle Year-round tilt 2.55 3.61 4.46 4.7 4.59 4.76 4.64 4.66 4.02 2.95 2.21 2.04 27° angle Best winter tilt 2.64 3.64 4.31 4.31 4.05 4.12 4.05 4.20 3.81 2.93 2.26 2.12 59° angle Best summer tilt 2.33 3.40 4.40 4.87 4.93 5.23 5.04 4.91 4.04 2.83 2.04 1.85 Tilt adjusted each month 2.64 27° 3.65 35° 4.46 43° 4.88 51° 4.93 59° 5.52 66° 5.04 59° 4.95 51° 4.02 43° 2.96 35° 2.26 27° 2.13 20°

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 1.11 1.98 3.25 4.79 5.60 5.78 6.23 5.06 3.65 2.28 1.36 0.91 Upright - 0° 1.94 2.77 3.32 3.57 3.21 3.00 3.33 3.36 3.33 2.90 2.30 1.74 40° angle Year-round tilt 2.02 3.10 4.16 5.15 5.15 4.99 5.54 5.11 4.40 3.36 2.41 1.76 24° angle Best winter tilt 2.08 3.11 4.00 4.71 4.51 4.36 4.78 4.58 4.16 3.33 2.48 1.83 56° angle Best summer tilt 1.85 2.92 4.11 5.34 5.56 5.51 6.04 5.39 4.42 3.21 2.22 1.59 Tilt adjusted each month 2.08 24° 3.12 32° 4.16 40° 5.35 48° 5.56 56° 5.85 64° 6.04 56° 5.44 48° 4.44 40° 3.37 32° 2.48 24° 1.84 16°

Solar insolation values - Ireland

Borders Region

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 0.57 1.25 2.34 3.96 5.34 5.41 4.92 4.10 2.87 1.53 0.71 0.4 Upright - 0° 1.06 1.85 2.44 3.13 3.31 3.04 2.89 2.90 2.77 2.05 1.23 0.81 35° angle Year-round tilt 1.10 2.03 2.98 4.25 4.89 4.61 4.31 4.10 3.50 2.32 1.29 0.82 19° angle Best winter tilt 1.12 2.02 2.83 3.87 4.33 4.03 3.79 3.66 3.29 2.28 1.31 0.84 51° angle Best summer tilt 1.01 1.94 2.98 4.44 5.32 5.09 4.75 4.36 3.55 2.25 1.21 0.75 Tilt adjusted each month 1.12 19° 2.04 27° 2.98 35° 4.46 43° 5.32 51° 5.47 58° 4.75 51° 4.43 43° 3.50 35° 2.32 27° 1.31 19° 0.84 12°

Dublin, The Midlands and Midlands-East Regions

 Flat - 90° 0.62 1.19 2.09 3.34 4.32 4.36 4.21 3.52 2.53 1.44 0.82 0.5 Upright - 0° 1.03 1.59 1.97 2.45 2.61 2.46 2.44 2.37 2.25 1.78 1.33 0.92 37° angle Year-round tilt 1.08 1.78 2.48 3.42 3.90 3.76 3.70 3.42 2.93 2.05 1.41 0.94 21° angle Best winter tilt 1.10 1.77 2.34 3.10 3.47 3.3 3.26 3.06 2.74 2.01 1.43 0.97 53° angle Best summer tilt 1.01 1.71 2.50 3.59 4.25 4.14 4.05 3.64 2.98 1.99 1.32 0.87 Tilt adjusted each month 1.10 21° 1.79 29° 2.48 37° 3.62 45° 4.25 53° 4.42 60° 4.05 53° 3.71 45° 2.93 37° 2.05 29° 1.43 21° 0.97 14°

South-East, West and South West Regions

 Flat - 90° 0.67 1.26 2.15 3.46 4.46 4.53 4.41 3.72 2.66 1.52 0.87 0.56 Upright - 0° 1.06 1.65 2.00 2.52 2.66 2.51 2.52 2.48 2.35 1.86 1.37 0.99 38° angle Year-round tilt 1.13 1.86 2.53 3.54 4.04 3.90 3.88 3.63 3.08 2.16 1.47 1.02 22° angle Best winter tilt 1.15 1.84 2.40 3.22 3.59 3.43 3.43 3.25 2.88 2.12 1.49 1.05 54° angle Best summer tilt 1.05 1.79 2.55 3.72 4.39 4.30 4.25 3.86 3.13 2.10 1.37 0.94 Tilt adjusted each month 1.15 22° 1.87 30° 2.53 38° 3.74 46° 4.39 54° 4.58 62° 4.25 54° 3.92 46° 3.08 38° 2.16 30° 1.49 22° 1.05 14°

Solar insolation values - New Zealand

North Island

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 6.41 5.65 4.59 3.31 2.35 1.96 2.18 2.83 3.96 4.82 5.86 6.26 Upright - 0° 2.58 2.87 3.23 3.36 3.14 3.05 3.20 3.17 3.20 2.73 2.55 2.46 53° angle Year-round tilt 5.80 5.54 5.10 4.27 3.47 3.14 3.39 3.82 4.63 4.92 5.41 5.57 37° angle Best winter tilt 5.07 5.03 4.87 4.3 3.64 3.36 3.60 3.91 4.52 4.56 4.79 4.83 69° angle Best summer tilt 6.27 5.79 5.06 4.02 3.12 2.75 2.99 3.53 4.51 5.05 5.79 6.06 Tilt adjusted each month 6.27 69° 5.81 61° 5.10 53° 4.32 45° 3.64 37° 3.41 30° 3.60 37° 3.91 45° 4.63 53° 5.05 61° 5.79 69° 6.27 76°

South Island

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 5.75 5.01 3.92 2.67 1.82 1.36 1.60 2.28 3.39 4.50 5.49 5.82 Upright - 0° 2.75 2.94 3.18 3.14 3.05 2.64 3.01 3.08 3.17 2.90 2.76 2.67 46° angle Year-round tilt 5.21 4.98 4.56 3.77 3.19 2.63 3.03 3.49 4.23 4.66 5.09 5.07 30° angle Best winter tilt 4.54 4.50 4.34 3.78 3.35 2.81 3.23 3.57 4.10 4.28 4.47 4.39 62° angle Best summer tilt 5.64 5.23 4.55 3.56 2.85 2.30 2.67 3.23 4.13 4.82 5.47 5.55 Tilt adjusted each month 5.64 62° 5.26 54° 4.56 46° 3.80 38° 3.35 30° 2.84 22° 3.23 30° 3.57 38° 4.23 46° 4.82 54° 5.47 62° 5.84 70°

Solar insolation values - United Kingdom

London

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 0.75 1.37 2.31 3.57 4.59 4.86 4.82 4.20 2.81 1.69 0.92 0.60 Upright - 0° 1.20 1.80 2.18 2.58 2.7 2.64 2.71 2.80 2.47 2.07 1.43 1.01 38° angle Year-round tilt 1.27 2.04 2.76 3.67 4.17 4.2 4.25 4.16 3.26 2.41 1.53 1.05 22° angle Best winter tilt 1.30 2.03 2.62 3.34 3.66 3.69 3.76 3.73 3.06 2.37 1.56 1.08 54° angle Best summer tilt 1.19 1.95 2.77 3.84 4.52 4.63 4.66 4.41 3.31 2.33 1.43 0.97 Tilt adjusted each month 1.30 22° 2.05 30° 2.76 38° 3.86 46° 4.52 54° 4.91 62° 4.66 54° 4.46 46° 3.26 38° 2.41 30° 1.56 22° 1.08 14°

South East

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 0.80 1.44 2.42 3.70 4.73 4.99 5.00 4.31 2.88 1.75 0.95 0.62 Upright - 0° 1.34 1.94 2.33 2.71 2.8 2.72 2.81 2.9 2.57 2.18 1.51 1.09 38° angle Year-round tilt 1.41 2.18 2.94 3.84 4.31 4.32 4.42 4.3 3.37 2.53 1.61 1.12 22° angle Best winter tilt 1.44 2.18 2.81 3.5 3.79 3.80 3.92 3.86 3.17 2.49 1.64 1.16 54° angle Best summer tilt 1.30 2.08 2.94 4.01 4.68 4.76 4.85 4.55 3.41 2.43 1.50 1.03 Tilt adjusted each month 1.44 22° 2.20 30° 2.94 38° 4.03 46° 4.68 54° 5.05 62° 4.85 54° 4.60 46° 3.37 38° 2.53 30° 1.64 22° 1.16 14°

South West

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 0.81 1.51 2.49 3.91 5.13 5.37 5.28 4.37 3.07 1.74 1.01 0.65 Upright - 0° 1.26 1.98 2.36 2.83 2.97 2.84 2.9 2.88 2.72 2.09 1.54 1.08 39° angle Year-round tilt 1.34 2.25 3.00 4.07 4.7 4.64 4.68 4.34 3.60 2.45 1.65 1.13 23° angle Best winter tilt 1.37 2.24 2.86 3.72 4.13 4.08 4.07 3.90 3.40 2.41 1.68 1.16 55° angle Best summer tilt 1.25 2.14 3.00 4.24 5.08 5.12 5.12 4.59 3.64 2.36 1.54 1.04 Tilt adjusted each month 1.37 23° 2.26 31° 3.00 39° 4.26 47° 5.08 55° 5.43 62° 5.12 55° 4.65 47° 3.60 39° 2.45 31° 1.68 23° 1.16 16°

East of England

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 0.72 1.34 2.37 3.60 4.68 4.90 4.86 4.20 2.82 1.64 0.91 0.57 Upright - 0° 1.18 1.80 2.30 2.63 2.78 2.68 2.75 2.83 2.52 2.04 1.45 1.01 38° angle Year-round tilt 1.25 2.03 2.89 3.71 4.24 4.21 4.27 4.16 3.30 2.36 1.55 1.04 22° angle Best winter tilt 1.27 2.02 2.74 3.38 3.77 3.69 3.77 3.73 3.10 2.32 1.57 1.07 54° angle Best summer tilt 1.16 1.94 2.90 3.89 4.61 4.65 4.69 4.41 3.35 2.29 1.45 0.96 Tilt adjusted each month 1.27 22° 2.04 30° 2.89 38° 3.91 46° 4.61 54° 4.96 62° 4.69 54° 4.48 46° 3.30 38° 2.37 30° 1.57 22° 1.07 14°

East Midlands

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 0.64 1.31 2.20 3.37 4.44 4.51 4.50 3.82 2.59 1.54 0.8 0.51 Upright - 0° 1.07 1.80 2.11 2.47 2.67 2.53 2.59 2.59 2.31 1.93 1.27 0.94 37° angle Year-round tilt 1.13 2.01 2.64 3.45 4.01 3.88 3.95 3.74 3.01 2.22 1.36 0.96 21° angle Best winter tilt 1.15 2.00 2.51 3.13 3.56 3.40 3.48 3.35 2.81 2.18 1.37 0.99 53° angle Best summer tilt 1.05 1.92 2.66 3.62 4.37 4.28 4.33 3.98 3.06 2.15 1.27 0.89 Tilt adjusted each month 1.15 21° 2.02 29° 2.64 37° 3.65 45° 4.37 53° 4.57 60° 4.33 53° 4.05 45° 3.01 37° 2.22 29° 1.37 21° 0.99 14°

West Midlands

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 0.71 1.35 2.28 3.47 4.51 4.69 4.69 4.04 2.70 1.65 0.90 0.57 Upright - 0° 1.18 1.84 2.18 2.54 2.70 2.59 2.68 2.73 2.41 2.08 1.45 1.03 38° angle Year-round tilt 1.24 2.06 2.74 3.56 4.09 4.05 4.14 3.99 3.14 2.4 1.55 1.06 22° angle Best winter tilt 1.26 2.05 2.60 3.25 3.64 3.55 3.65 3.58 2.95 2.36 1.57 1.09 54° angle Best summer tilt 1.15 1.97 2.75 3.73 4.45 4.46 4.53 4.23 3.19 2.31 1.44 0.97 Tilt adjusted each month 1.26 22° 2.07 30° 2.74 38° 3.76 46° 4.45 54° 4.74 62° 4.53 54° 4.30 46° 3.14 38° 2.40 30° 1.57 22° 1.09 14°

North-East England

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 0.61 1.35 2.45 3.88 5.35 5.47 5.13 4.29 2.91 1.66 0.77 0.44 Upright - 0° 1.17 2.03 2.61 3.04 3.31 3.06 3.01 3.05 2.81 2.27 1.38 0.94 35° angle Year-round tilt 1.21 2.23 3.17 4.14 4.9 4.65 4.49 4.32 3.56 2.56 1.44 0.95 19° angle Best winter tilt 1.24 2.22 3.03 3.76 4.33 4.07 3.95 3.85 3.34 2.52 1.46 0.98 51° angle Best summer tilt 1.11 2.12 3.17 4.33 5.33 5.15 4.96 4.59 3.60 2.46 1.34 0.86 Tilt adjusted each month 1.24 19° 2.24 27° 3.17 35° 4.36 43° 5.33 51° 5.53 58° 4.96 51° 4.66 43° 3.56 35° 2.56 27° 1.46 19° 0.98 12°

North-West England

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 0.66 1.32 2.30 3.63 4.92 5.00 4.88 3.98 2.73 1.53 0.79 0.50 Upright - 0° 1.16 1.85 2.28 2.74 2.99 2.79 2.82 2.74 2.51 1.95 1.29 0.95 36° angle Year-round tilt 1.21 2.06 2.83 3.79 4.49 4.31 4.31 3.94 3.23 2.23 1.37 0.96 20° angle Best winter tilt 1.24 2.05 2.69 3.46 4.00 3.78 3.8 3.54 3.04 2.19 1.39 0.99 52° angle Best summer tilt 1.12 1.96 2.83 3.97 4.89 4.77 4.73 4.18 3.28 2.16 1.28 0.88 Tilt adjusted each month 1.24 20° 2.07 28° 2.83 36° 3.99 44° 4.89 52° 5.08 60° 4.73 52° 4.25 44° 3.23 36° 2.23 28° 1.39 20° 1.00 12°

Yorkshire and the Humber

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 0.62 1.30 2.30 3.51 4.69 4.78 4.64 3.89 2.67 1.54 0.75 0.47 Upright - 0° 1.12 1.86 2.31 2.64 2.86 2.68 2.7 2.68 2.46 1.99 1.25 0.92 36° angle Year-round tilt 1.16 2.06 2.85 3.64 4.24 4.09 4.07 3.83 3.16 2.28 1.32 0.94 20° angle Best winter tilt 1.19 2.04 2.71 3.31 3.77 3.58 3.58 3.42 2.96 2.24 1.34 0.97 52° angle Best summer tilt 1.08 1.96 2.86 3.82 4.63 4.50 4.47 4.08 3.21 2.2 1.24 0.86 Tilt adjusted each month 1.19 20° 2.06 28° 2.85 36° 3.85 44° 4.63 52° 4.83 60° 4.47 52° 4.15 44° 3.16 36° 2.28 28° 1.34 20° 0.97 12°

Central and Southern Scotland

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 0.51 1.16 2.03 3.22 4.55 4.66 4.31 3.63 2.42 1.33 0.64 0.38 Upright - 0° 0.99 1.75 2.05 2.46 2.85 2.68 2.58 2.55 2.28 1.76 1.14 0.86 34° angle Year-round tilt 1.02 1.91 2.51 3.32 4.11 3.97 3.77 3.52 2.87 1.99 1.20 0.86 18° angle Best winter tilt 1.04 1.90 2.37 3.00 3.64 3.47 3.31 3.17 2.68 1.95 1.21 0.89 50° angle Best summer tilt 0.94 1.83 2.53 3.49 4.49 4.37 4.15 3.77 2.93 1.93 1.12 0.78 Tilt adjusted each month 1.04 18° 1.92 26° 2.51 34° 3.53 42° 4.49 50° 4.72 58° 4.15 50° 3.86 42° 2.87 34° 1.99 26° 1.21 18° 0.89 10°

North Scotland

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 0.47 1.11 2.05 3.30 4.52 4.63 4.31 3.61 2.45 1.31 0.59 0.32 Upright - 0° 0.99 1.74 2.16 2.59 2.88 2.7 2.61 2.57 2.38 1.80 1.12 0.77 33° angle Year-round tilt 1.00 1.88 2.62 3.44 4.08 3.93 3.75 3.50 2.96 2.01 1.16 0.76 17° angle Best winter tilt 1.03 1.87 2.46 3.12 3.62 3.43 3.30 3.15 2.77 1.97 1.18 0.79 49° angle Best summer tilt 0.92 1.80 2.61 3.62 4.46 4.32 4.11 3.75 3.02 1.95 1.08 0.69 Tilt adjusted each month 1.03 17° 1.89 25° 2.62 33° 3.66 41° 4.46 49° 4.69 56° 4.11 49° 3.84 41° 2.96 33° 2.01 25° 1.18 17° 0.79 10°

South Wales

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 0.72 1.33 2.21 3.52 4.57 4.75 4.71 3.97 2.71 1.55 0.89 0.59 Upright - 0° 1.14 1.74 2.04 2.54 2.7 2.59 2.66 2.64 2.37 1.87 1.35 0.99 38° angle Year-round tilt 1.21 1.97 2.59 3.61 4.15 4.11 4.16 3.91 3.12 2.18 1.45 1.03 22° angle Best winter tilt 1.23 1.96 2.46 3.29 3.65 3.61 3.68 3.51 2.93 2.14 1.47 1.06 54° angle Best summer tilt 1.13 1.89 2.61 3.78 4.51 4.52 4.56 4.14 3.17 2.11 1.36 0.95 Tilt adjusted each month 1.23 22° 1.98 30° 2.59 38° 3.80 46° 4.51 54° 4.80 62° 4.56 54° 4.20 46° 3.12 38° 2.18 30° 1.47 22° 1.06 14°

North Wales

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 0.66 1.32 2.30 3.63 4.92 5.00 4.88 3.98 2.73 1.53 0.79 0.50 Upright - 0° 1.14 1.83 2.26 2.72 2.97 2.77 2.81 2.72 2.49 1.93 1.27 0.92 37° angle Year-round tilt 1.19 2.04 2.81 3.78 4.48 4.30 4.29 3.93 3.22 2.22 1.35 0.95 21° angle Best winter tilt 1.22 2.03 2.68 3.44 3.98 3.77 3.79 3.52 3.02 2.18 1.37 0.98 53° angle Best summer tilt 1.11 1.95 2.82 3.96 4.88 4.76 4.72 4.18 3.27 2.15 1.26 0.87 Tilt adjusted each month 1.22 21° 2.05 29° 2.81 37° 3.98 45° 4.88 53° 5.08 60° 4.72 53° 4.24 45° 3.22 37° 2.22 29° 1.37 21° 0.98 14°

Northern Ireland

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 0.61 1.25 2.15 3.39 4.54 4.54 4.30 3.64 2.56 1.42 0.74 0.43 Upright - 0° 1.09 1.79 2.12 2.55 2.79 2.58 2.54 2.51 2.36 1.82 1.25 0.82 35° angle Year-round tilt 1.13 1.98 2.62 3.51 4.12 3.9 3.79 3.56 3.02 2.08 1.32 0.83 19° angle Best winter tilt 1.16 1.97 2.49 3.19 3.66 3.42 3.34 3.19 2.83 2.04 1.34 0.86 51° angle Best summer tilt 1.05 1.89 2.64 3.68 4.49 4.27 4.15 3.79 3.07 2.02 1.24 0.77 Tilt adjusted each month 1.16 19° 1.99 27° 2.62 35° 3.71 43° 4.49 51° 4.59 58° 4.15 51° 3.86 43° 3.02 35° 2.08 27° 1.34 19° 0.86 12°

Solar insolation values - United States of America

Alabama

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 2.32 2.9 4.06 5.01 5.54 5.64 5.7 5.14 4.58 3.84 2.68 2.17 Upright - 0° 2.94 2.85 3.06 2.67 2.30 2.15 2.22 2.46 3.03 3.72 3.29 3.00 58° angle Year-round tilt 3.29 3.64 4.60 5.04 5.10 5.02 5.14 4.96 4.98 4.86 3.76 3.22 42° angle Best winter tilt 3.45 3.68 4.46 4.65 4.52 4.36 4.49 4.50 4.75 4.90 3.92 3.42 74° angle Best summer tilt 2.96 3.42 4.5 5.18 5.46 5.45 5.55 5.20 4.96 4.56 3.39 2.85 Tilt adjusted each month 3.45 42° 3.69 50° 4.60 58° 5.18 66° 5.46 74° 5.64 82° 5.55 74° 5.22 66° 4.98 58° 4.92 50° 3.92 42° 3.45 34°

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 0.40 1.07 2.22 3.73 4.95 5.26 4.86 3.86 2.46 1.37 0.58 0.00 Upright - 0° 0.88 1.75 2.51 3.09 3.22 3.08 2.98 2.83 2.47 2.00 1.20 0.00 32° angle Year-round tilt 0.89 1.89 2.97 4.06 4.50 4.47 4.24 3.81 3.03 2.21 1.23 0.00 16° angle Best winter tilt 0.92 1.88 2.83 3.68 3.99 3.90 3.73 3.43 2.84 2.17 1.25 0.00 48° angle Best summer tilt 0.82 1.80 2.97 4.25 4.93 4.93 4.66 4.07 3.09 2.13 1.14 0.00 Tilt adjusted each month 0.92 16° 1.90 24° 2.97 32° 4.27 40° 4.93 48° 5.35 56° 4.66 48° 4.16 40° 3.03 32° 2.21 24° 1.25 16° 0.00 8°

Arizona

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 3.20 4.07 5.45 6.62 7.37 7.52 6.78 5.97 5.45 4.48 3.50 2.95 Upright - 0° 4.63 4.59 4.29 3.33 2.57 2.28 2.34 2.70 3.60 4.51 4.76 4.63 57° angle Year-round tilt 4.92 5.55 6.45 6.83 6.74 6.57 6.08 5.78 6.03 5.82 5.24 4.74 41° angle Best winter tilt 5.28 5.74 6.34 6.33 5.87 5.58 5.26 5.22 5.78 5.93 5.57 5.14 73° angle Best summer tilt 4.28 5.04 6.20 6.96 7.26 7.23 6.60 6.05 5.95 5.39 4.60 4.06 Tilt adjusted each month 5.28 41° 5.74 49° 6.45 57° 6.97 65° 7.26 73° 7.52 80° 6.60 73° 6.07 65° 6.03 57° 5.94 49° 5.57 41° 5.24 34°

Arkansas

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 2.39 3.03 4.01 5.19 5.51 5.91 6.02 5.52 4.74 3.71 2.60 2.15 Upright - 0° 3.14 3.09 3.07 2.80 2.33 2.22 2.31 2.64 3.20 3.62 3.23 3.02 55° angle Year-round tilt 3.45 3.88 4.56 5.24 5.10 5.26 5.44 5.36 5.20 4.70 3.66 3.21 39° angle Best winter tilt 3.64 3.94 4.44 4.84 4.52 4.57 4.76 4.86 4.98 4.74 3.82 3.42 71° angle Best summer tilt 3.08 3.62 4.46 5.38 5.44 5.72 5.88 5.61 5.16 4.41 3.30 2.83 Tilt adjusted each month 3.64 39° 3.94 47° 4.56 55° 5.38 63° 5.44 71° 5.91 78° 5.88 71° 5.63 63° 5.20 55° 4.75 47° 3.82 39° 3.45 32°

California

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 2.18 3.09 4.65 6.08 7.21 7.93 7.79 7.02 5.64 4.12 2.63 1.99 Upright - 0° 3.35 3.68 4.09 3.53 2.96 2.69 2.82 3.46 4.34 4.83 3.96 3.37 51° angle Year-round tilt 3.52 4.36 5.72 6.32 6.64 6.91 6.95 6.95 6.64 5.86 4.23 3.41 35° angle Best winter tilt 3.73 4.46 5.61 5.83 5.79 5.84 5.95 6.25 6.39 5.98 4.47 3.66 67° angle Best summer tilt 3.12 4.02 5.52 6.49 7.16 7.63 7.60 7.29 6.52 5.40 3.75 2.97 Tilt adjusted each month 3.73 35° 4.46 43° 5.72 51° 6.49 59° 7.16 67° 7.95 74° 7.60 67° 7.31 59° 6.64 51° 5.98 43° 4.47 35° 3.71 28°

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 2.41 3.27 4.49 5.42 6.28 6.70 6.35 5.68 5.03 3.90 2.67 2.18 Upright - 0° 4.20 4.18 4.05 3.25 2.80 2.60 2.64 2.99 3.90 4.66 4.30 4.21 50° angle Year-round tilt 4.27 4.85 5.58 5.62 5.81 5.90 5.72 5.60 5.87 5.60 4.52 4.12 34° angle Best winter tilt 4.58 4.99 5.47 5.17 5.10 5.05 4.96 5.05 5.63 5.71 4.79 4.47 66° angle Best summer tilt 3.72 4.43 5.39 5.78 6.24 6.47 6.21 5.87 5.79 5.17 3.98 3.53 Tilt adjusted each month 4.58 34° 4.99 42° 5.58 50° 5.78 58° 6.24 66° 6.73 74° 6.21 66° 5.89 58° 5.87 50° 5.71 42° 4.79 34° 4.56 26°

Connecticut

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 1.88 2.73 3.76 4.52 5.23 5.80 5.54 5.00 4.11 3.01 1.97 1.63 Upright - 0° 3.20 3.50 3.41 2.83 2.57 2.52 2.54 2.79 3.23 3.45 3.00 3.01 48° angle Year-round tilt 3.29 4.05 4.62 4.65 4.85 5.07 5.01 4.92 4.73 4.17 3.21 3.00 32° angle Best winter tilt 3.49 4.14 4.50 4.28 4.28 4.38 4.37 4.45 4.51 4.20 3.35 3.21 64° angle Best summer tilt 2.91 3.73 4.50 4.80 5.20 5.53 5.42 5.16 4.71 3.92 2.88 2.61 Tilt adjusted each month 3.49 32° 4.14 40° 4.62 48° 4.80 56° 5.20 64° 5.81 72° 5.42 64° 5.19 56° 4.73 48° 4.21 40° 3.35 32° 3.25 24°

Delaware

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 1.97 2.73 3.69 4.65 5.27 5.67 5.50 5.05 4.25 3.33 2.24 1.77 Upright - 0° 2.99 3.16 3.10 2.77 2.46 2.36 2.40 2.68 3.15 3.65 3.21 2.93 51° angle Year-round tilt 3.17 3.78 4.35 4.73 4.86 5.01 4.95 4.92 4.78 4.51 3.50 3.00 35° angle Best winter tilt 3.34 3.84 4.22 4.36 4.29 4.34 4.32 4.44 4.56 4.54 3.66 3.20 67° angle Best summer tilt 2.82 3.52 4.26 4.89 5.21 5.47 5.36 5.17 4.77 4.23 3.14 2.64 Tilt adjusted each month 3.34 35° 3.85 43° 4.35 51° 4.89 59° 5.21 67° 5.68 74° 5.36 67° 5.20 59° 4.78 51° 4.56 43° 3.66 35° 3.23 28°

Florida

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 3.56 4.44 5.29 6.11 6.49 5.97 5.55 5.26 4.76 4.52 3.78 3.35 Upright - 0° 4.03 4.07 3.44 2.62 2.06 1.88 1.91 2.15 2.68 3.68 4.04 4.07 63° angle Year-round tilt 4.66 5.39 5.80 6.11 5.98 5.38 5.08 5.06 4.96 5.27 4.85 4.51 47° angle Best winter tilt 4.96 5.56 5.69 5.68 5.28 4.69 4.50 4.62 4.75 5.33 5.11 4.85 79° angle Best summer tilt 4.11 4.94 5.61 6.23 6.39 5.82 5.45 5.26 4.93 4.93 4.32 3.92 Tilt adjusted each month 4.96 47° 5.56 55° 5.80 63° 6.23 71° 6.39 79° 5.97 86° 5.45 79° 5.28 71° 4.96 63° 5.34 55° 5.11 47° 4.92 40°

Georgia

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 2.50 3.12 4.28 5.19 5.80 5.59 5.72 5.17 4.46 3.91 2.82 2.36 Upright - 0° 3.21 3.14 3.23 2.74 2.34 2.13 2.21 2.46 2.92 3.76 3.48 3.32 56° angle Year-round tilt 3.55 3.96 4.86 5.24 5.36 5.00 5.18 5.01 4.82 4.92 3.96 3.52 40° angle Best winter tilt 3.74 4.02 4.74 4.86 4.74 4.37 4.55 4.55 4.60 4.97 4.15 3.76 72° angle Best summer tilt 3.17 3.69 4.74 5.38 5.72 5.42 5.58 5.23 4.80 4.60 3.55 3.09 Tilt adjusted each month 3.74 40° 4.03 48° 4.86 56° 5.38 64° 5.72 72° 5.59 80° 5.58 72° 5.25 64° 4.82 56° 4.98 48° 4.15 40° 3.80 32°

Hawaii

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 4.09 5.06 5.85 6.58 6.97 7.35 7.21 6.88 6.36 5.41 4.34 3.90 Upright - 0° 4.06 4.12 3.33 2.33 1.77 2.80 1.69 2.01 3.00 3.96 4.22 4.12 69° angle Year-round tilt 4.98 5.84 6.24 6.50 6.43 7.37 6.52 6.63 6.60 6.10 5.24 4.83 53° angle Best winter tilt 5.29 6.03 6.13 6.04 5.65 6.92 5.65 6.03 6.34 6.20 5.56 5.19 85° angle Best summer tilt 4.40 5.34 6.03 6.62 6.89 7.43 7.08 6.88 6.50 5.67 4.65 4.21 Tilt adjusted each month 5.29 53° 6.03 61° 6.24 69° 6.63 77° 6.89 85° 7.46 92° 7.08 85° 6.89 77° 6.60 69° 6.21 61° 5.56 53° 5.27 46°

Idaho

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 1.72 2.66 4.07 5.38 6.36 7.24 7.37 6.44 4.99 3.43 1.97 1.49 Upright - 0° 3.17 3.67 4.01 3.53 3.08 2.98 3.18 3.66 4.33 4.56 3.35 3.00 47° angle Year-round tilt 3.21 4.15 5.28 5.72 5.92 6.26 6.56 6.51 6.14 5.28 3.49 2.96 31° angle Best winter tilt 3.41 4.25 5.16 5.26 5.17 5.31 5.61 5.85 5.89 5.38 3.67 3.17 63° angle Best summer tilt 2.83 3.82 5.10 5.88 6.38 6.89 7.16 6.83 6.04 4.88 3.11 2.57 Tilt adjusted each month 3.41 31° 4.25 39° 5.28 47° 5.88 55° 6.38 63° 7.26 70° 7.16 63° 6.85 55° 6.14 47° 5.38 39° 3.67 31° 3.21 24°

Illinois

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 1.92 2.55 3.62 4.69 5.40 5.90 6.12 5.38 4.57 3.32 2.10 1.71 Upright - 0° 2.91 2.91 3.06 2.83 2.54 2.44 2.59 2.86 3.48 3.70 2.95 2.84 50° angle Year-round tilt 3.08 3.48 4.28 4.80 5.01 5.23 5.52 5.29 5.24 4.53 3.22 2.90 34° angle Best winter tilt 3.24 3.53 4.15 4.42 4.42 4.52 4.80 4.78 5.01 4.58 3.36 3.09 66° angle Best summer tilt 2.74 3.25 4.19 4.95 5.36 5.71 5.99 5.54 5.19 4.24 2.90 2.55 Tilt adjusted each month 3.24 34° 3.54 42° 4.28 50° 4.95 58° 5.36 66° 5.92 74° 5.99 66° 5.57 58° 5.24 50° 4.59 42° 3.36 34° 3.12 26°

Indiana

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 1.83 2.54 3.55 4.49 5.19 5.91 5.98 5.24 4.55 3.26 2.02 1.57 Upright - 0° 2.70 2.89 2.99 2.70 2.46 2.44 2.56 2.80 3.46 3.60 2.78 2.47 50° angle Year-round tilt 2.87 3.46 4.18 4.57 4.80 5.24 5.40 5.15 5.21 4.42 3.05 2.56 34° angle Best winter tilt 3.02 3.51 4.05 4.21 4.25 4.53 4.70 4.65 4.98 4.46 3.17 2.72 66° angle Best summer tilt 2.57 3.24 4.10 4.71 5.14 5.72 5.85 5.39 5.17 4.15 2.76 2.27 Tilt adjusted each month 3.02 34° 3.52 42° 4.18 50° 4.72 58° 5.14 66° 5.93 74° 5.85 66° 5.42 58° 5.21 50° 4.48 42° 3.17 34° 2.74 26°

Iowa

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 1.91 2.56 3.62 4.56 5.39 6.12 6.02 5.32 4.41 3.14 2.02 1.64 Upright - 0° 3.26 3.15 3.23 2.84 2.62 2.59 2.67 2.94 3.50 3.67 3.10 3.04 48° angle Year-round tilt 3.35 3.68 4.40 4.68 4.99 5.33 5.43 5.26 5.13 4.42 3.31 3.04 32° angle Best winter tilt 3.55 3.74 4.27 4.31 4.40 4.59 4.71 4.74 4.90 4.46 3.46 3.25 64° angle Best summer tilt 2.96 3.42 4.30 4.84 5.36 5.83 5.90 5.52 5.09 4.14 2.97 2.65 Tilt adjusted each month 3.55 32° 3.75 40° 4.40 48° 4.84 56° 5.36 64° 6.13 72° 5.90 64° 5.55 56° 5.13 48° 4.47 40° 3.46 32° 3.29 24°

Kansas

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 2.15 2.72 3.91 4.80 5.61 6.15 6.37 5.48 4.67 3.41 2.30 1.92 Upright - 0° 3.40 3.13 3.32 2.84 2.56 2.46 2.60 2.86 3.50 3.76 3.32 3.32 51° angle Year-round tilt 3.57 3.75 4.66 4.89 5.16 5.41 5.70 5.36 5.33 4.64 3.61 3.36 35° angle Best winter tilt 3.78 3.81 4.53 4.50 4.54 4.65 4.93 4.83 5.09 4.68 3.78 3.60 67° angle Best summer tilt 3.16 3.50 4.55 5.05 5.54 5.93 6.21 5.63 5.29 4.35 3.24 2.93 Tilt adjusted each month 3.78 35° 3.81 43° 4.66 51° 5.06 59° 5.54 67° 6.17 74° 6.21 67° 5.66 59° 5.33 51° 4.69 43° 3.78 35° 3.64 28°

Louisiana

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 2.59 3.25 4.31 5.21 5.79 5.65 5.66 5.30 4.72 4.03 3.04 2.56 Upright - 0° 2.95 3.02 3.01 2.57 2.19 2.00 2.07 2.34 2.89 3.55 3.42 3.22 60° angle Year-round tilt 3.41 3.95 4.76 5.23 5.35 5.07 5.14 5.11 5.02 4.85 4.03 3.54 44° angle Best winter tilt 3.57 4.00 4.63 4.86 4.75 4.43 4.53 4.65 4.80 4.89 4.21 3.77 76° angle Best summer tilt 3.08 3.69 4.65 5.35 5.71 5.48 5.53 5.33 4.99 4.55 3.63 3.13 Tilt adjusted each month 3.57 44° 4.01 52° 4.76 60° 5.35 68° 5.71 76° 5.65 84° 5.53 76° 5.35 68° 5.02 60° 4.90 52° 4.21 44° 3.80 36°

Maine

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 1.69 2.57 3.64 4.43 4.87 5.35 5.28 4.85 3.78 2.56 1.60 1.33 Upright - 0° 3.25 3.61 3.52 2.91 2.52 2.50 2.56 2.84 3.10 3.01 2.51 2.57 46° angle Year-round tilt 3.28 4.07 4.63 4.59 4.50 4.64 4.69 4.80 4.39 3.60 2.68 2.58 30° angle Best winter tilt 3.48 4.16 4.50 4.21 3.96 4.01 4.09 4.32 4.17 3.60 2.78 2.74 62° angle Best summer tilt 2.88 3.75 4.52 4.76 4.84 5.09 5.10 5.05 4.39 3.41 2.43 2.27 Tilt adjusted each month 3.48 30° 4.16 38° 4.63 46° 4.76 54° 4.84 62° 5.37 70° 5.10 62° 5.09 54° 4.39 46° 3.62 38° 2.78 30° 2.76 22°

Maryland

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 1.94 2.68 3.67 4.63 5.31 5.58 5.53 4.94 4.19 3.33 2.19 1.71 Upright - 0° 2.89 3.06 3.06 2.75 2.47 2.33 2.40 2.62 3.09 3.63 3.08 2.75 51° angle Year-round tilt 3.09 3.68 4.31 4.70 4.89 4.93 4.97 4.80 4.70 4.50 3.37 2.84 35° angle Best winter tilt 3.24 3.73 4.18 4.33 4.31 4.27 4.34 4.34 4.47 4.53 3.52 3.02 67° angle Best summer tilt 2.76 3.44 4.23 4.86 5.24 5.38 5.39 5.04 4.69 4.22 3.04 2.51 Tilt adjusted each month 3.24 35° 3.74 43° 4.31 51° 4.87 59° 5.24 67° 5.59 74° 5.39 67° 5.08 59° 4.70 51° 4.55 43° 3.52 35° 3.04 28°

Massachusetts

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 1.80 2.62 3.61 4.46 5.13 5.50 5.60 4.99 4.04 2.93 1.89 1.54 Upright - 0° 3.15 3.40 3.30 2.83 2.56 2.47 2.59 2.81 3.22 3.41 2.94 2.91 48° angle Year-round tilt 3.22 3.91 4.44 4.59 4.75 4.79 5.05 4.91 4.67 4.10 3.13 2.90 32° angle Best winter tilt 3.42 3.99 4.32 4.22 4.19 4.15 4.40 4.43 4.45 4.12 3.27 3.10 64° angle Best summer tilt 2.85 3.62 4.34 4.74 5.10 5.24 5.49 5.16 4.66 3.86 2.82 2.53 Tilt adjusted each month 3.42 32° 3.99 40° 4.44 48° 4.75 56° 5.10 64° 5.51 72° 5.49 64° 5.19 56° 4.67 48° 4.14 40° 3.27 32° 3.14 24°

Michigan

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 1.78 2.51 3.44 4.45 5.24 6.07 5.93 5.03 4.13 2.79 1.69 1.41 Upright - 0° 3.13 3.22 3.11 2.84 2.61 2.64 2.70 2.86 3.33 3.20 2.47 2.55 47° angle Year-round tilt 3.20 3.71 4.20 4.59 4.86 5.29 5.36 4.97 4.81 3.86 2.67 2.56 31° angle Best winter tilt 3.39 3.78 4.07 4.22 4.29 4.55 4.65 4.49 4.59 3.87 2.77 2.73 63° angle Best summer tilt 2.83 3.44 4.11 4.74 5.21 5.78 5.82 5.22 4.78 3.64 2.43 2.25 Tilt adjusted each month 3.39 31° 3.78 39° 4.20 47° 4.74 55° 5.21 63° 6.09 70° 5.82 63° 5.25 55° 4.81 47° 3.89 39° 2.77 31° 2.75 24°

Minnesota

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 1.71 2.55 3.44 4.54 5.32 5.96 6.05 5.19 4.00 2.78 1.76 1.37 Upright - 0° 3.41 3.65 3.33 3.03 2.75 2.73 2.87 3.08 3.39 3.49 3.03 2.81 45° angle Year-round tilt 3.39 4.08 4.36 4.76 4.96 5.19 5.40 5.20 4.76 4.08 3.15 2.77 29° angle Best winter tilt 3.62 4.18 4.24 4.37 4.36 4.47 4.68 4.68 4.54 4.12 3.30 2.97 61° angle Best summer tilt 2.97 3.74 4.25 4.91 5.33 5.68 5.87 5.46 4.73 3.83 2.82 2.42 Tilt adjusted each month 3.62 29° 4.18 37° 4.36 45° 4.92 53° 5.33 61° 5.99 68° 5.87 61° 5.48 53° 4.76 45° 4.13 37° 3.30 29° 3.00 22°

Mississippi

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 2.52 3.24 4.24 5.34 5.89 5.98 5.80 5.36 4.75 3.99 2.94 2.39 Upright - 0° 3.08 3.20 3.09 2.72 2.30 2.12 2.17 2.46 3.04 3.71 3.53 3.17 58° angle Year-round tilt 3.48 4.07 4.75 5.39 5.43 5.33 5.25 5.17 5.12 4.94 4.05 3.44 42° angle Best winter tilt 3.66 4.14 4.62 5.00 4.80 4.62 4.60 4.70 4.90 4.99 4.24 3.65 74° angle Best summer tilt 3.12 3.79 4.64 5.52 5.80 5.79 5.66 5.41 5.09 4.63 3.64 3.03 Tilt adjusted each month 3.66 42° 4.14 50° 4.75 58° 5.52 66° 5.80 74° 5.98 82° 5.66 74° 5.43 66° 5.12 58° 5.00 50° 4.24 42° 3.69 34°

Missouri

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 2.09 2.71 3.85 4.94 5.53 5.95 6.18 5.52 4.62 3.42 2.23 1.89 Upright - 0° 3.13 3.04 3.21 2.90 2.52 2.40 2.54 2.85 3.42 3.70 3.07 3.10 51° angle Year-round tilt 3.32 3.67 4.54 5.05 5.11 5.27 5.57 5.41 5.24 4.59 3.37 3.17 35° angle Best winter tilt 3.51 3.72 4.41 4.65 4.51 4.55 4.84 4.89 5.01 4.63 3.52 3.38 67° angle Best summer tilt 2.95 3.42 4.43 5.20 5.47 5.74 6.04 5.67 5.20 4.30 3.04 2.77 Tilt adjusted each month 3.51 35° 3.73 43° 4.54 51° 5.20 59° 5.47 67° 5.96 74° 6.04 67° 5.70 59° 5.24 51° 4.65 43° 3.52 35° 3.42 28°

Montana

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 1.64 2.51 3.65 4.72 5.60 6.31 6.58 5.70 4.30 2.83 1.83 1.37 Upright - 0° 2.59 3.19 3.41 3.22 2.95 2.94 3.18 3.45 3.62 3.31 2.73 2.25 43° angle Year-round tilt 2.73 3.67 4.48 4.98 5.21 5.48 5.87 5.71 5.04 3.95 2.94 2.34 27° angle Best winter tilt 2.83 3.69 4.33 4.58 4.59 4.71 5.08 5.14 4.79 3.94 3.03 2.44 59° angle Best summer tilt 2.48 3.45 4.41 5.14 5.61 6.00 6.39 6.00 5.04 3.76 2.70 2.12 Tilt adjusted each month 2.83 27° 3.71 35° 4.48 43° 5.15 51° 5.61 59° 6.34 66° 6.39 59° 6.04 51° 5.04 43° 3.97 35° 3.03 27° 2.45 20°

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 2.09 2.68 3.83 4.78 5.57 6.35 6.35 5.48 4.63 3.35 2.26 1.86 Upright - 0° 3.55 3.26 3.39 2.93 2.64 2.60 2.71 2.97 3.63 3.90 3.51 3.50 49° angle Year-round tilt 3.65 3.82 4.65 4.91 5.16 5.54 5.73 5.41 5.38 4.70 3.72 3.47 33° angle Best winter tilt 3.88 3.90 4.53 4.53 4.55 4.77 4.96 4.89 5.15 4.76 3.92 3.74 65° angle Best summer tilt 3.20 3.55 4.53 5.07 5.54 6.06 6.22 5.67 5.33 4.39 3.32 3.00 Tilt adjusted each month 3.88 33° 3.90 41° 4.65 49° 5.07 57° 5.54 65° 6.36 72° 6.22 65° 5.70 57° 5.38 49° 4.77 41° 3.92 33° 3.79 26°

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 2.29 3.15 4.61 5.85 7.01 7.77 7.76 6.89 5.60 4.06 2.60 2.11 Upright - 0° 3.84 3.94 4.16 3.48 2.98 2.74 2.90 3.49 4.42 4.91 4.10 3.95 51° angle Year-round tilt 3.95 4.60 5.75 6.10 6.47 6.77 6.93 6.85 6.67 5.89 4.33 3.91 35° angle Best winter tilt 4.21 4.72 5.64 5.61 5.64 5.72 5.93 6.15 6.41 6.01 4.58 4.22 67° angle Best summer tilt 3.46 4.22 5.55 6.26 6.97 7.47 7.58 7.17 6.55 5.42 3.83 3.36 Tilt adjusted each month 4.21 35° 4.72 43° 5.75 51° 6.26 59° 6.97 67° 7.79 74° 7.58 67° 7.20 59° 6.67 51° 6.01 43° 4.58 35° 4.30 28°

New Hampshire

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 1.74 2.62 3.61 4.43 4.92 5.42 5.47 4.91 3.92 2.72 1.71 1.46 Upright - 0° 3.17 3.54 3.38 2.85 2.51 2.48 2.58 2.82 3.16 3.17 2.63 2.86 47° angle Year-round tilt 3.23 4.03 4.51 4.57 4.55 4.71 4.90 4.85 4.54 3.80 2.81 2.84 31° angle Best winter tilt 3.42 4.12 4.38 4.20 4.01 4.08 4.26 4.36 4.31 3.81 2.92 3.03 63° angle Best summer tilt 2.85 3.72 4.40 4.73 4.89 5.16 5.32 5.10 4.53 3.59 2.54 2.47 Tilt adjusted each month 3.42 31° 4.12 39° 4.51 47° 4.74 55° 4.89 63° 5.43 70° 5.32 63° 5.13 55° 4.54 47° 3.83 39° 2.92 31° 3.07 24°

New Jersey

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 1.92 2.71 3.69 4.57 5.21 5.61 5.51 4.97 4.15 3.13 2.07 1.66 Upright - 0° 3.03 3.25 3.18 2.77 2.49 2.39 2.45 2.69 3.15 3.47 2.99 2.83 50° angle Year-round tilt 3.18 3.84 4.41 4.66 4.81 4.96 4.97 4.85 4.70 4.26 3.24 2.88 34° angle Best winter tilt 3.35 3.91 4.28 4.28 4.25 4.29 4.33 4.38 4.48 4.28 3.38 3.07 66° angle Best summer tilt 2.82 3.57 4.32 4.81 5.16 5.42 5.38 5.10 4.69 4.01 2.93 2.53 Tilt adjusted each month 3.35 34° 3.91 42° 4.41 50° 4.82 58° 5.16 66° 5.63 74° 5.38 66° 5.13 58° 4.70 50° 4.30 42° 3.38 34° 3.10 26°

New Mexico

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 3.04 3.85 5.14 6.32 7.04 7.22 6.51 5.81 5.41 4.39 3.29 2.81 Upright - 0° 4.80 4.49 4.27 3.39 2.70 2.42 2.44 2.79 3.80 4.73 4.83 4.87 54° angle Year-round tilt 4.98 5.39 6.20 6.48 6.47 6.33 5.85 5.66 6.11 5.93 5.18 4.85 38° angle Best winter tilt 5.36 5.56 6.10 5.98 5.66 5.40 5.08 5.12 5.87 6.05 5.52 5.28 70° angle Best summer tilt 4.31 4.91 5.96 6.65 6.96 6.95 6.34 5.92 6.02 5.47 4.54 4.13 Tilt adjusted each month 5.36 38° 5.56 46° 6.20 54° 6.65 62° 6.96 70° 7.22 78° 6.34 70° 5.95 62° 6.11 54° 6.05 46° 5.52 38° 5.40 30°

New York

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 1.74 2.60 3.57 4.34 5.04 5.64 5.55 4.97 3.95 2.80 1.76 1.47 Upright - 0° 3.02 3.39 3.27 2.76 2.54 2.52 2.58 2.82 3.15 3.22 2.63 2.73 47° angle Year-round tilt 3.09 3.89 4.40 4.46 4.67 4.92 5.02 4.91 4.56 3.88 2.83 2.73 31° angle Best winter tilt 3.28 3.97 4.27 4.10 4.13 4.26 4.37 4.43 4.35 3.89 2.94 2.91 63° angle Best summer tilt 2.74 3.60 4.29 4.61 5.01 5.37 5.44 5.16 4.55 3.66 2.56 2.39 Tilt adjusted each month 3.28 31° 3.97 39° 4.40 47° 4.62 55° 5.01 63° 5.65 70° 5.44 63° 5.19 55° 4.56 47° 3.91 39° 2.94 31° 2.94 24°

North Carolina

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 2.43 3.05 4.20 5.22 5.73 5.80 5.68 5.08 4.43 3.76 2.73 2.30 Upright - 0° 3.39 3.24 3.33 2.87 2.43 2.25 2.30 2.52 3.05 3.82 3.64 3.56 54° angle Year-round tilt 3.66 4.00 4.87 5.29 5.29 5.16 5.15 4.93 4.86 4.87 4.03 3.67 38° angle Best winter tilt 3.87 4.07 4.75 4.89 4.69 4.49 4.51 4.47 4.64 4.93 4.24 3.94 70° angle Best summer tilt 3.24 3.72 4.74 5.44 5.66 5.61 5.55 5.15 4.84 4.55 3.60 3.20 Tilt adjusted each month 3.87 38° 4.07 46° 4.87 54° 5.44 62° 5.66 70° 5.80 78° 5.55 70° 5.18 62° 4.86 54° 4.94 46° 4.24 38° 4 30°

North Dakota

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 1.48 2.35 3.47 4.77 5.72 6.26 6.49 5.48 4.06 2.73 1.71 1.27 Upright - 0° 2.36 3.02 3.29 3.29 3.06 2.98 3.22 3.39 3.47 3.25 2.61 2.15 43° angle Year-round tilt 2.49 3.46 4.28 5.01 5.27 5.43 5.79 5.50 4.78 3.85 2.80 2.22 27° angle Best winter tilt 2.58 3.48 4.13 4.60 4.63 4.67 5.01 4.95 4.54 3.83 2.88 2.32 59° angle Best summer tilt 2.28 3.26 4.22 5.19 5.68 5.96 6.30 5.78 4.78 3.67 2.57 2.01 Tilt adjusted each month 2.58 27° 3.50 35° 4.28 43° 5.19 51° 5.68 59° 6.30 66° 6.30 59° 5.82 51° 4.78 43° 3.87 35° 2.88 27° 2.32 20°

Ohio

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 1.77 2.49 3.31 4.47 5.18 5.64 5.76 5.11 4.26 3.08 1.86 1.46 Upright - 0° 2.64 2.86 2.76 2.70 2.47 2.39 2.51 2.74 3.23 3.37 2.51 2.28 50° angle Year-round tilt 2.81 3.43 3.86 4.54 4.77 4.98 5.18 4.99 4.84 4.16 2.78 2.38 34° angle Best winter tilt 2.95 3.47 3.73 4.17 4.21 4.31 4.50 4.50 4.61 4.18 2.88 2.51 66° angle Best summer tilt 2.53 3.21 3.80 4.69 5.12 5.44 5.62 5.24 4.82 3.92 2.54 2.12 Tilt adjusted each month 2.95 34° 3.47 42° 3.86 50° 4.70 58° 5.12 66° 5.66 74° 5.62 66° 5.28 58° 4.84 50° 4.20 42° 2.88 34° 2.52 26°

Oklahoma

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 2.59 3.20 4.29 5.40 5.84 6.32 6.73 5.86 4.81 3.72 2.75 2.33 Upright - 0° 3.70 3.43 3.39 2.94 2.44 2.31 2.46 2.79 3.31 3.73 3.64 3.59 54° angle Year-round tilt 3.97 4.23 4.98 5.47 5.38 5.59 6.03 5.70 5.32 4.79 4.05 3.71 38° angle Best winter tilt 4.21 4.31 4.86 5.05 4.75 4.82 5.22 5.15 5.09 4.83 4.25 3.98 70° angle Best summer tilt 3.50 3.92 4.85 5.63 5.76 6.10 6.55 5.97 5.28 4.49 3.62 3.23 Tilt adjusted each month 4.21 38° 4.31 46° 4.98 54° 5.63 62° 5.76 70° 6.33 78° 6.55 70° 5.99 62° 5.32 54° 4.85 46° 4.25 38° 4.04 30°

Oregon

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 1.41 2.24 3.26 4.33 5.26 6.19 6.85 6.04 4.55 2.82 1.49 1.16 Upright - 0° 2.40 2.91 3.03 2.83 2.68 2.74 3.06 3.48 3.91 3.47 2.23 2.04 46° angle Year-round tilt 2.49 3.35 4.02 4.47 4.86 5.35 6.07 6.07 5.53 4.10 2.41 2.09 30° angle Best winter tilt 2.61 3.39 3.89 4.10 4.27 4.58 5.20 5.44 5.28 4.12 2.49 2.20 62° angle Best summer tilt 2.23 3.12 3.95 4.64 5.23 5.88 6.63 6.39 5.47 3.85 2.20 1.86 Tilt adjusted each month 2.61 30° 3.40 38° 4.02 46° 4.64 54° 5.23 62° 6.22 70° 6.63 62° 6.42 54° 5.53 46° 4.14 38° 2.49 30° 2.21 22°

Pennsylvania

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 1.87 2.65 3.52 4.32 5.11 5.44 5.50 4.86 4.03 3.07 1.97 1.58 Upright - 0° 2.91 3.16 3.00 2.63 2.46 2.35 2.45 2.64 3.05 3.39 2.78 2.62 50° angle Year-round tilt 3.07 3.74 4.17 4.38 4.71 4.82 4.96 4.74 4.55 4.16 3.03 2.69 34° angle Best winter tilt 3.23 3.80 4.04 4.03 4.17 4.18 4.33 4.28 4.33 4.18 3.16 2.86 66° angle Best summer tilt 2.73 3.48 4.09 4.53 5.05 5.26 5.37 4.98 4.54 3.92 2.75 2.38 Tilt adjusted each month 3.23 34° 3.80 42° 4.17 50° 4.54 58° 5.05 66° 5.46 74° 5.37 66° 5.01 58° 4.55 50° 4.20 42° 3.16 34° 2.88 26°

Rhode Island

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 1.89 2.69 3.75 4.54 5.31 5.76 5.57 5.07 4.13 3.07 1.98 1.62 Upright - 0° 3.25 3.44 3.40 2.85 2.60 2.52 2.55 2.83 3.26 3.58 3.04 2.99 48° angle Year-round tilt 3.33 3.97 4.61 4.67 4.93 5.04 5.04 5.01 4.76 4.31 3.24 2.98 32° angle Best winter tilt 3.53 4.06 4.49 4.30 4.35 4.36 4.40 4.52 4.55 4.34 3.39 3.19 64° angle Best summer tilt 2.93 3.67 4.49 4.82 5.28 5.49 5.45 5.25 4.74 4.03 2.91 2.60 Tilt adjusted each month 3.53 32° 4.06 40° 4.61 48° 4.82 56° 5.28 64° 5.77 72° 5.45 64° 5.28 56° 4.76 48° 4.36 40° 3.39 32° 3.23 24°

South Carolina

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 2.52 3.14 4.28 5.41 5.88 5.90 5.75 5.13 4.44 3.80 2.83 2.39 Upright - 0° 3.33 3.19 3.26 2.85 2.37 2.18 2.23 2.46 2.93 3.67 3.59 3.49 56° angle Year-round tilt 3.67 4.03 4.89 5.47 5.40 5.23 5.18 4.95 4.81 4.80 4.05 3.67 40° angle Best winter tilt 3.87 4.09 4.76 5.05 4.77 4.53 4.53 4.49 4.58 4.83 4.25 3.93 72° angle Best summer tilt 3.27 3.76 4.77 5.62 5.79 5.70 5.60 5.19 4.79 4.50 3.64 3.22 Tilt adjusted each month 3.87 40° 4.09 48° 4.89 56° 5.62 64° 5.79 72° 5.90 80° 5.60 72° 5.21 64° 4.81 56° 4.85 48° 4.25 40° 3.97 32°

South Dakota

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 1.75 2.54 3.61 4.79 5.83 6.51 6.60 5.75 4.42 3.04 1.93 1.47 Upright - 0° 3.44 3.52 3.48 3.16 2.91 2.84 2.99 3.33 3.77 3.91 3.40 3.04 46° angle Year-round tilt 3.45 3.98 4.58 5.02 5.41 5.62 5.85 5.76 5.33 4.57 3.53 3.01 30° angle Best winter tilt 3.68 4.07 4.45 4.60 4.73 4.80 5.03 5.17 5.08 4.62 3.71 3.21 62° angle Best summer tilt 3.03 3.67 4.47 5.19 5.83 6.19 6.39 6.06 5.28 4.27 3.14 2.62 Tilt adjusted each month 3.68 30° 4.07 38° 4.58 46° 5.19 54° 5.83 62° 6.54 70° 6.39 62° 6.09 54° 5.33 46° 4.63 38° 3.71 30° 3.25 22°

Tennessee

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 2.06 2.72 3.83 4.97 5.47 5.79 5.79 5.30 4.63 3.62 2.43 1.88 Upright - 0° 2.72 2.81 3.00 2.77 2.38 2.26 2.33 2.63 3.23 3.69 3.13 2.69 54° angle Year-round tilt 3.00 3.51 4.38 5.02 5.04 5.13 5.22 5.14 5.13 4.70 3.52 2.87 38° angle Best winter tilt 3.14 3.54 4.25 4.63 4.46 4.45 4.55 4.65 4.90 4.74 3.67 3.03 70° angle Best summer tilt 2.71 3.29 4.30 5.17 5.40 5.58 5.64 5.39 5.10 4.41 3.18 2.55 Tilt adjusted each month 3.14 38° 3.55 46° 4.38 54° 5.18 62° 5.40 70° 5.79 78° 5.64 70° 5.42 62° 5.13 54° 4.76 46° 3.67 38° 3.05 30°

Texas

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 2.83 3.41 4.40 5.25 5.62 6.36 6.56 5.94 4.97 4.05 3.07 2.63 Upright - 0° 3.35 3.21 3.07 2.57 2.16 2.05 2.14 2.50 3.03 3.55 3.45 3.35 60° angle Year-round tilt 3.82 4.18 4.86 5.27 5.19 5.65 5.90 5.72 5.31 4.87 4.07 3.67 44° angle Best winter tilt 4.03 4.25 4.74 4.89 4.61 4.88 5.12 5.18 5.08 4.90 4.25 3.91 76° angle Best summer tilt 3.41 3.89 4.75 5.39 5.54 6.15 6.38 5.98 5.27 4.57 3.66 3.24 Tilt adjusted each month 4.03 44° 4.25 52° 4.86 60° 5.39 68° 5.54 76° 6.36 84° 6.38 76° 6.00 68° 5.31 60° 4.92 52° 4.25 44° 3.95 36°

Utah

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 2.31 3.11 4.47 5.54 6.55 7.31 7.08 6.11 5.10 3.76 2.45 2.07 Upright - 0° 4.10 3.99 4.10 3.36 2.91 2.73 2.83 3.21 4.03 4.53 3.92 4.07 50° angle Year-round tilt 4.17 4.62 5.61 5.76 6.04 6.38 6.33 6.04 6.01 5.43 4.14 3.99 34° angle Best winter tilt 4.46 4.74 5.49 5.30 5.27 5.41 5.43 5.43 5.76 5.52 4.37 4.32 66° angle Best summer tilt 3.64 4.24 5.42 5.93 6.51 7.03 6.91 6.34 5.93 5.03 3.67 3.43 Tilt adjusted each month 4.46 34° 4.74 42° 5.61 50° 5.93 58° 6.51 66° 7.34 74° 6.91 66° 6.37 58° 6.01 50° 5.53 42° 4.37 34° 4.39 26°

Vermont

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 1.61 2.53 3.54 4.34 4.86 5.43 5.49 4.81 3.72 2.45 1.50 1.26 Upright - 0° 3.06 3.55 3.42 2.87 2.53 2.54 2.65 2.84 3.06 2.85 2.30 2.38 46° angle Year-round tilt 3.08 4.00 4.49 4.51 4.50 4.72 4.89 4.77 4.33 3.41 2.46 2.40 30° angle Best winter tilt 3.27 4.09 4.37 4.14 3.97 4.08 4.26 4.30 4.11 3.41 2.55 2.54 62° angle Best summer tilt 2.72 3.68 4.38 4.66 4.84 5.17 5.31 5.02 4.32 3.24 2.24 2.11 Tilt adjusted each month 3.27 30° 4.09 38° 4.49 46° 4.67 54° 4.84 62° 5.45 70° 5.31 62° 5.05 54° 4.33 46° 3.43 38° 2.55 30° 2.56 22°

Virginia

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 2.17 2.83 3.89 4.76 5.38 5.63 5.56 4.98 4.28 3.58 2.43 1.94 Upright - 0° 3.11 3.10 3.15 2.73 2.42 2.28 2.34 2.56 3.04 3.79 3.32 3.00 53° angle Year-round tilt 3.34 3.79 4.53 4.82 4.97 5.00 5.02 4.83 4.74 4.75 3.65 3.12 37° angle Best winter tilt 3.52 3.84 4.40 4.44 4.39 4.34 4.39 4.38 4.52 4.79 3.82 3.32 69° angle Best summer tilt 2.98 3.53 4.43 4.97 5.31 5.44 5.42 5.07 4.72 4.44 3.28 2.74 Tilt adjusted each month 3.52 37° 3.85 45° 4.53 53° 4.97 61° 5.31 69° 5.64 76° 5.42 69° 5.09 61° 4.74 53° 4.81 45° 3.82 37° 3.35 30°

Washington

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 1.06 1.93 2.94 4.05 4.99 5.51 5.88 5.20 3.98 2.25 1.25 0.91 Upright - 0° 1.55 2.42 2.69 2.76 2.73 2.72 2.97 3.23 3.42 2.62 1.79 1.43 43° angle Year-round tilt 1.68 2.79 3.52 4.15 4.55 4.76 5.21 5.18 4.68 3.13 1.95 1.51 27° angle Best winter tilt 1.72 2.79 3.37 3.80 4.01 4.10 4.51 4.65 4.43 3.10 1.99 1.56 59° angle Best summer tilt 1.56 2.65 3.50 4.33 4.91 5.24 5.68 5.47 4.70 3.00 1.82 1.39 Tilt adjusted each month 1.72 27° 2.81 35° 3.532 43° 4.34 51° 4.91 59° 5.55 66° 5.68 59° 5.51 51° 4.68 43° 3.14 35° 1.99 27° 1.56 20°

West Virginia

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 1.85 2.49 3.51 4.58 5.09 5.82 5.63 4.99 4.31 3.33 2.12 1.65 Upright - 0° 2.56 2.66 2.84 2.68 2.37 2.36 2.39 2.61 3.14 3.53 2.81 2.46 52° angle Year-round tilt 2.79 3.27 4.05 4.64 4.70 5.15 5.07 4.85 4.82 4.42 3.13 2.59 36° angle Best winter tilt 2.91 3.29 3.92 4.27 4.16 4.45 4.43 4.39 4.59 4.44 3.25 2.74 68° angle Best summer tilt 2.51 3.07 3.98 4.79 5.03 5.62 5.49 5.09 4.80 4.15 2.84 2.31 Tilt adjusted each month 2.91 36° 3.30 44° 4.05 52° 4.79 60° 5.03 68° 5.83 76° 5.49 68° 5.12 60° 4.82 52° 4.46 44° 3.25 36° 2.75 28°

Wisconsin

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 1.80 2.67 3.58 4.49 5.33 5.97 5.87 5.05 4.01 2.76 1.79 1.52 Upright - 0° 3.34 3.63 3.34 2.89 2.67 2.63 2.71 2.89 3.25 3.23 2.82 3.05 47° angle Year-round tilt 3.39 4.13 4.45 4.64 4.92 5.18 5.24 4.99 4.67 3.87 3.00 3.01 31° angle Best winter tilt 3.60 4.22 4.32 4.25 4.33 4.45 4.54 4.49 4.44 3.88 3.12 3.22 63° angle Best summer tilt 2.98 3.81 4.35 4.80 5.30 5.67 5.71 5.25 4.66 3.65 2.70 2.61 Tilt adjusted each month 3.60 31° 4.22 39° 4.45 47° 4.80 55° 5.30 63° 5.99 70° 5.71 63° 5.29 55° 4.67 47° 3.90 39° 3.12 31° 3.26 24°

Wyoming

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flat - 90° 2.13 2.92 4.10 5.13 6.14 6.92 6.65 5.82 4.79 3.52 2.34 1.89 Upright - 0° 3.81 3.78 3.76 3.18 2.84 2.73 2.80 3.15 3.83 4.28 3.83 3.76 49° angle Year-round tilt 3.88 4.37 5.12 5.32 5.66 5.98 5.96 5.76 5.65 5.11 4.03 3.69 33° angle Best winter tilt 4.13 4.47 4.99 4.89 4.96 5.09 5.13 5.18 5.40 5.18 4.25 3.99 65° angle Best summer tilt 3.39 4.02 4.97 5.49 6.10 6.58 6.50 6.05 5.59 4.75 3.58 3.18 Tilt adjusted each month 4.13 33° 4.47 41° 5.12 49° 5.49 57° 6.10 65° 6.93 72° 6.50 65° 6.08 57° 5.65 49° 5.19 41° 4.25 33° 4.05 26°

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