Example Data Table
| Panel Watts |
Panels |
Peak Sun Hours |
Derating Factor |
Net Daily kWh |
Monthly kWh |
| 450 |
10 |
5.2 |
78% |
18.25 |
555.5 |
| 550 |
16 |
4.8 |
76% |
32.10 |
976.8 |
| 400 |
6 |
5.0 |
80% |
9.60 |
292.2 |
Formula Used
System size kW = panel watts × panel count ÷ 1000.
Gross daily kWh = system size kW × peak sun hours.
Combined factor = availability × inverter efficiency × battery efficiency × remaining loss factors.
Net daily kWh = gross daily kWh × combined factor.
Period kWh = net daily kWh × selected days.
Yearly kWh = net daily kWh × 365.
Required panels = target daily kWh ÷ net daily kWh per panel.
How to Use This Calculator
Enter the rated watts for one solar panel. Add the number of panels in the array. Enter local peak sun hours, not total daylight hours. Add expected loss values for heat, shade, dust, cable, inverter, battery, and age. Use 100 percent battery efficiency when there is no battery. Enter your tariff to estimate savings. Enter your carbon factor to estimate yearly offset. Press calculate to view output above the form. Use the CSV or PDF button to save the same result.
Solar Energy Planning
A solar power kWh calculator helps size a photovoltaic system before buying equipment. It turns panel rating, panel count, peak sun hours, and losses into usable energy. The result is not a promise. It is a planning estimate. Good inputs make the estimate stronger.
Why kWh Matters
Kilowatt hours show how much energy your system can deliver. One kWh can run a 100 watt load for ten hours. Solar panels are rated in watts, but bills use kWh. This calculator bridges that gap. It also shows daily, monthly, yearly, and selected period output.
Losses and Efficiency
Real systems never produce nameplate power all day. Heat reduces module output. Dust blocks light. Shade can affect one panel or a string. Cable resistance wastes a small amount. Inverters and batteries also have efficiency limits. The calculator combines these derating values. This gives a net energy estimate after common losses.
Using the Result
Compare daily kWh against your average daily load. If output is lower, increase panel count or improve sun access. Check monthly production against your bill. Use annual output for payback studies. Use the target daily energy field to estimate panel quantity. The roof area field helps confirm space needs.
Better Input Practice
Use local peak sun hours, not daylight hours. Peak sun hours measure useful solar intensity. Use a conservative value when weather is uncertain. Enter realistic shading and soiling values. Clean panels may use a low soiling loss. Dusty or coastal sites may need a higher value. For battery systems, include round trip efficiency. For grid tied systems without storage, set battery efficiency to 100 percent.
Planning Notes
This tool supports early design decisions. It does not replace a site survey. Wire sizing, inverter clipping, tilt, azimuth, code rules, and utility limits still matter. Use the estimate to compare options. Then confirm the final design with local solar data and qualified electrical guidance.
Cost and Impact Review
Energy is only one part of solar value. The tariff field estimates bill savings. The carbon factor estimates avoided emissions. These values depend on local prices and grid mix. Treat them as adjustable assumptions. Save the CSV or PDF output when comparing different system choices later. Keep better records.
FAQs
What is a solar power kWh calculator?
It estimates usable solar energy from panel rating, panel count, sun hours, and system losses. It returns daily, monthly, yearly, and selected period kWh values.
Are peak sun hours the same as daylight hours?
No. Peak sun hours represent strong solar energy equivalent to full rated sunlight. A location can have many daylight hours but fewer peak sun hours.
Why is net kWh lower than gross kWh?
Net kWh includes derating losses. Common losses come from heat, shading, dust, cable resistance, inverter conversion, battery cycling, and panel aging.
What battery efficiency should I enter?
Use the battery round trip efficiency from the battery data sheet. For systems without battery storage, enter 100 percent.
Can this calculator size my complete system?
It gives an early energy estimate. Final design also needs inverter limits, wiring, roof layout, tilt, orientation, local rules, and safety checks.
How do I estimate required panels?
Enter your target daily kWh. The calculator divides that target by the estimated net daily energy from one panel.
What is specific yield?
Specific yield shows yearly kWh per installed kW. It helps compare performance across different system sizes and locations.
Why add electricity tariff?
The tariff converts estimated energy into possible bill savings. Actual savings depend on usage timing, net metering, taxes, and utility policy.