Peak Sun Hours

Understanding Peak Sun Hours

I get asked all the time, “How much solar energy can I expect to produce in my area?” and “How sunny is my area?”

We answer that question with Peak Sun Hours. Peak Sun Hours is the technical term we use to describe the amount of sunlight a location receives. It’s not just the number of hours between sunrise and sunset, but it takes into account cloud cover, weather patterns, and more.

The super technical definition is that it’s the number of hours of sunlight at 1,000 watts per square meter (1 kW/m²) – the standard testing condition for rating solar panels.

Throughout the day, sunlight intensity varies dramatically. Early morning and late evening provide lower intensity (200-500 W/m²), while midday can exceed 1,000 W/m² in ideal conditions. Peak sun hours aggregate all this varying sunlight into equivalent hours at peak intensity. For example, receiving 500 W/m² for 2 hours equals 1 peak sun hour (500 × 2 = 1,000).

Of course, sunlight varies dramatically by time of year and location. You’ll really enjoy using our interactive tool below to see how your region compares to others. For example, Phoenix, Arizona produces 35% more solar energy than Chicago, Illinois.

How to Read This Data: The grid below shows the total solar energy production per month for a 10kW system in each city. This monthly energy production directly correlates to the peak sun hours available in that location. Higher monthly energy values indicate more peak sun hours and better solar potential for your investment.

Select Cities to Compare

Phoenix

AZ

Annual Production

17,662 kWh

100

75

50

25

0

Jan: 38.3 kWh/day

Feb: 42.2 kWh/day

Mar: 50 kWh/day

Apr: 57.4 kWh/day

May: 58.3 kWh/day

Jun: 57.9 kWh/day

Jul: 50.8 kWh/day

Aug: 49.9 kWh/day

Sep: 49.6 kWh/day

Oct: 45.6 kWh/day

Nov: 41.2 kWh/day

Dec: 37.8 kWh/day

Chicago

IL

Annual Production

13,080 kWh

100

75

50

25

0

Jan: 21.1 kWh/day

Feb: 28.8 kWh/day

Mar: 35.1 kWh/day

Apr: 42.4 kWh/day

May: 44.9 kWh/day

Jun: 48.5 kWh/day

Jul: 51.2 kWh/day

Aug: 44.8 kWh/day

Sep: 40.2 kWh/day

Oct: 30.2 kWh/day

Nov: 23.2 kWh/day

Dec: 18.4 kWh/day

15,371

Average Annual kWh

Across selected cities

Phoenix

Best Performance

17,662 kWh/year

35%

Production Range

Best vs. lowest performer

Solar Production Rankings

Annual production for 10kW systems across all service areas

Rank City Annual Production Daily Average Best Month Worst Month
1 Phoenix, AZ 17,662 kWh 48.4 kWh May: 58.3 kWh/day Dec: 37.8 kWh/day
2 Mesa, AZ 17,551 kWh 48.1 kWh May: 58.2 kWh/day Jan: 37.6 kWh/day
3 Los Angeles, CA 16,861 kWh 46.2 kWh Aug: 56.2 kWh/day Dec: 32.4 kWh/day
4 San Jose, CA 16,473 kWh 45.1 kWh Jul: 60.5 kWh/day Jan: 26.2 kWh/day
5 Sacramento, CA 16,267 kWh 44.6 kWh Jul: 59.6 kWh/day Dec: 23.9 kWh/day
6 San Diego, CA 16,045 kWh 44.0 kWh Aug: 51.7 kWh/day Dec: 33.4 kWh/day
7 Denver, CO 15,992 kWh 43.8 kWh Jun: 53.4 kWh/day Dec: 31 kWh/day
8 Tampa, FL 15,772 kWh 43.2 kWh Apr: 50.5 kWh/day Dec: 35.5 kWh/day
9 San Francisco, CA 15,693 kWh 43.0 kWh Jun: 55.7 kWh/day Dec: 25.7 kWh/day
10 Miami, FL 15,539 kWh 42.6 kWh Mar: 49.2 kWh/day Dec: 35.4 kWh/day
11 Orlando, FL 15,485 kWh 42.4 kWh Apr: 49.5 kWh/day Dec: 34.3 kWh/day
12 Dallas, TX 15,091 kWh 41.3 kWh Jun: 50.5 kWh/day Dec: 31.9 kWh/day
13 San Antonio, TX 15,000 kWh 41.1 kWh Jul: 49 kWh/day Dec: 31.1 kWh/day
14 Austin, TX 14,860 kWh 40.7 kWh Aug: 49.7 kWh/day Dec: 32 kWh/day
15 Jacksonville, FL 14,671 kWh 40.2 kWh Apr: 47.6 kWh/day Dec: 30 kWh/day
16 Charleston, SC 14,626 kWh 40.1 kWh May: 48.2 kWh/day Dec: 27.7 kWh/day
17 Columbia, SC 14,535 kWh 39.8 kWh Jun: 47.6 kWh/day Dec: 29.7 kWh/day
18 Charlotte, NC 14,276 kWh 39.1 kWh Jun: 46.8 kWh/day Dec: 27.6 kWh/day
19 Houston, TX 14,261 kWh 39.1 kWh Jul: 45.2 kWh/day Dec: 27.8 kWh/day
20 Atlanta, GA 14,093 kWh 38.6 kWh May: 46.7 kWh/day Dec: 28.1 kWh/day
21 Baltimore, MD 13,930 kWh 38.2 kWh Jul: 48.1 kWh/day Dec: 24.8 kWh/day
22 Raleigh, NC 13,923 kWh 38.1 kWh Apr: 45.2 kWh/day Dec: 25.6 kWh/day
23 Durham, NC 13,850 kWh 37.9 kWh Jun: 46.2 kWh/day Dec: 28.1 kWh/day
24 Richmond, VA 13,607 kWh 37.3 kWh Jun: 47.2 kWh/day Dec: 25.2 kWh/day
25 Philadelphia, PA 13,588 kWh 37.2 kWh Jul: 47 kWh/day Dec: 23 kWh/day
26 Portland, ME 13,193 kWh 36.1 kWh Jun: 45.9 kWh/day Dec: 19.8 kWh/day
27 Boston, MA 13,110 kWh 35.9 kWh Jul: 46.5 kWh/day Dec: 19 kWh/day
28 Newark, NJ 13,105 kWh 35.9 kWh Jun: 46.6 kWh/day Dec: 21.9 kWh/day
29 Columbus, OH 13,093 kWh 35.9 kWh Jun: 47.7 kWh/day Dec: 19.6 kWh/day
30 Chicago, IL 13,080 kWh 35.8 kWh Jul: 51.2 kWh/day Dec: 18.4 kWh/day
31 Providence, RI 13,032 kWh 35.7 kWh Jul: 45 kWh/day Dec: 21.4 kWh/day
32 New York, NY 12,917 kWh 35.4 kWh Jun: 46 kWh/day Dec: 20.4 kWh/day
33 Detroit, MI 12,890 kWh 35.3 kWh Jul: 49.3 kWh/day Dec: 16.3 kWh/day
34 New Haven, CT 12,757 kWh 35.0 kWh Jul: 46.1 kWh/day Dec: 21 kWh/day
35 Cleveland, OH 12,731 kWh 34.9 kWh Jul: 50 kWh/day Dec: 14.6 kWh/day
36 Cincinnati, OH 12,581 kWh 34.5 kWh Jun: 43.6 kWh/day Dec: 21.1 kWh/day
37 Pittsburgh, PA 11,992 kWh 32.9 kWh Jul: 43.9 kWh/day Dec: 17.8 kWh/day

Data Source: NREL’s PVWatts Database

All solar irradiance and energy production data displayed in this tool comes from the National Renewable Energy Laboratory’s (NREL) PVWatts database. This comprehensive database takes into account numerous climate factors that affect solar energy production, including local weather patterns, atmospheric conditions, temperature variations, and seasonal changes.

The PVWatts system uses decades of meteorological data and sophisticated modeling to provide accurate estimates of solar potential across thousands of locations. This ensures that the peak sun hours and energy production figures you see reflect real-world conditions rather than theoretical maximums, giving you reliable data for making informed solar investment decisions.