Solar Panel Output Calculator
Estimate daily, monthly and annual generation from a solar array, with the bill saving it represents.
Every figure below is labelled in the currency you pick. Amounts are not converted — enter your own figures in that currency. To convert an amount at today’s rate, use the currency calculator.
Peak sun hours, not daylight hours
A peak sun hour is an hour at 1,000 W/m² of irradiance, which is the condition panels are rated at. A location with twelve hours of daylight might deliver only four peak sun hours. Typical annual averages run from about 2.5 in northern Europe to over 6 in desert regions, and the seasonal spread within one location is often three to one.
What this page needs from you
This page asks for system size in W, peak sun hours in h/day, system efficiency as a percentage and electricity price in $/kWh. From those it returns daily generation in kWh, together with monthly generation, annual generation, annual saving and co₂ avoided per year. Every figure updates as you type, and nothing you enter leaves your browser.
Running short costs more than over-ordering
A second delivery carries its own charge, materials from a different batch may not match, and a job halted halfway often has to be redone at the join. Ordering slightly long is cheap insurance against all three.
Measure twice, and allow for waste
A 5% error on one dimension becomes 10% on an area and 15% on a volume, which is why checking the tape matters more than the arithmetic. On top of the measured quantity, allow the trade standard of 10% for cuts and breakage, and 15 to 20% for diagonal layouts, complex shapes or anything cut around obstacles.
The formula
kWh/day = system watts × peak sun hours × system efficiency ÷ 1000
Every result on this page comes from this formula. Nothing is rounded until the final display, so figures match a spreadsheet to the cent.
How to use the Solar Panel Output Calculator
- Fill in each field with your own figures — the defaults are only there as an example.
- The result updates as you type, so there is no button to press.
- Check the breakdown under the main result for the supporting numbers.
- Use the copy button to take the result with you, or share the link to reload the same inputs.
Solar Panel Output Calculator — frequently asked questions
Is this solar panel output calculator free to use?
Yes. Every calculator on the site is free, needs no sign-up, and runs entirely in your browser, so your figures never leave your device.
How accurate is the result?
The maths is exact for the formula shown on the page. Accuracy in the real world depends on your inputs and on assumptions the formula cannot see, so treat the output as a well-grounded estimate rather than a quote.
Can I use it on my phone?
Yes. The page is responsive, weighs a few kilobytes and works offline once loaded, so it behaves the same on a phone as on a desktop.
What people search for
This page answers each of these searches. They are the exact phrases visitors use to find the solar panel output calculator.
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About this calculator
Written and reviewed by The Samsung Calculator editorial team. Every calculator is written against a published formula, reviewed against at least one independent reference implementation, and dated when it changes.
Last reviewed September 14, 2026 · Calculation runs client-side · No data collected · Report an error