Solar Generation Calculator
Find out how much electricity a solar system should produce where you live. This calculator uses long-term climate data for your location, then adjusts for panel direction, tilt, heat, shade, and system losses. It suits homeowners comparing roofs and anyone checking an installer's estimate.
Your solar generation
Your 5 kW system in Los Angeles could produce about 9,120 kWh a year, or about 25 kWh a day.
Likely yearly range
| Jan | 611 kWh |
|---|---|
| Feb | 621 kWh |
| Mar | 796 kWh |
| Apr | 836 kWh |
| May | 877 kWh |
| Jun | 862 kWh |
| Jul | 878 kWh |
| Aug | 887 kWh |
| Sep | 810 kWh |
| Oct | 744 kWh |
| Nov | 629 kWh |
| Dec | 568 kWh |
August is your best month, and December your lowest.
- Electricity you get9,119 (79%)
- System losses1,484 (13%)
- Heat691 (6%)
- Reflection303 (3%)
- Shade0 (0%)
Assumptions used
- Location
- 34.05, -118.24
- Sunlight on panels
- 2,319 kWh per m² a year
- Panel running temperature (NOCT)
- 45 °C
- Climate data
- NASA POWER, long-term monthly average
See the sun move across your panels
- Output now
- 3.74 kW
- Sun height
- 79°
- That day
- 28.7 kWh
| Point | Output |
|---|---|
| 00:00 | 0 |
| 01:00 | 0 |
| 02:00 | 0 |
| 03:00 | 0 |
| 04:00 | 0 |
| 05:00 | 0.07 |
| 06:00 | 0.56 |
| 07:00 | 1.4 |
| 08:00 | 2.24 |
| 09:00 | 2.96 |
| 10:00 | 3.49 |
| 11:00 | 3.75 |
| 12:00 | 3.74 |
| 13:00 | 3.45 |
| 14:00 | 2.91 |
| 15:00 | 2.19 |
| 16:00 | 1.37 |
| 17:00 | 0.54 |
| 18:00 | 0.07 |
| 19:00 | 0 |
| 20:00 | 0 |
| 21:00 | 0 |
| 22:00 | 0 |
| 23:00 | 0 |
What if?
Save this result, change any setting, and compare.
How this is calculated
Sunlight at your location
We start with NASA's 25-year monthly average of solar energy on flat ground and air temperature for your area. Each month is turned into a typical day using standard solar engineering models that split sunlight into direct and diffuse parts.
Sunlight on your panels
The sun's position is worked out for every hour of a typical day in each month. The Hay-Davies model then finds how much sunlight lands on a panel at your tilt and direction, including light reflected from the ground.
Electricity produced
Panels lose a little output to reflection, and more as they heat up. Shade and system losses such as dirt, wiring, and the inverter are removed last.
Output = size × sunlight on panel × temperature effect × (1 − shade) × (1 − system losses)
Worked example: a 5 kW system in Los Angeles
A 5 kW system in Los Angeles, tilted 25 degrees and facing south with 14% system losses, should produce about 9,120 kWh a year. That is about 1,824 kWh for each kW of panels.
Output peaks in August at about 890 kWh and is lowest in December at about 570 kWh.
How accurate is this?
We test this model against PVGIS, the European Commission's solar tool, at locations on five continents. Results usually land within 10% for a whole year, so we show a range. Single months vary more, and real years differ with the weather.
Common mistakes
- Using the panel rating as daily output. A 5 kW system rarely makes 5 kW for long
- Ignoring shade from trees, chimneys, or nearby buildings
- Comparing with one unusually sunny or cloudy year
- Assuming the steepest tilt is best. Direction often matters more
Limits of this tool
- Climate data covers an area of about 100 km, so it can miss local fog, hills, and microclimates
- Shade is a single yearly estimate here, not an hour-by-hour study
- This is an estimate for planning. It is not a performance guarantee
What to do next
- Ask installers for their expected kWh and compare it with this range
- Have an installer check shade on site before you commit
Frequently asked questions
How much electricity does a 5 kW solar system produce?
It depends mostly on location. In Los Angeles, a well-placed 5 kW system makes about 9,120 kWh a year. Sunnier places make more, and cloudier ones less.
Which direction should solar panels face?
Towards the equator is usually best for yearly output: south in the northern hemisphere and north in the southern hemisphere. East and west roofs can still work well, often at a modest loss.
Do solar panels work on cloudy days?
Yes, but output falls. Panels use diffuse light, so they keep producing under cloud at a much lower level.
Why is my real output lower than the panel rating?
Panel ratings are measured in lab conditions. On a roof, heat, dirt, wiring, the inverter, and the angle of the sun all reduce output.