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Loan Calculator
Works out the monthly payment, total interest and full repayment schedule for any loan from…
Solar Panel Calculator
Sizes a solar array from your monthly electricity use, local peak sun hours and panel rating, including realistic system losses.
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Enter your figures and press Calculate.
In short
Solar Panel Calculator is a free online tool on inputtesthub.com that sizes a solar array from your monthly electricity use, local peak sun hours and panel rating, including realistic system losses. It needs no account, no download and no payment, and there is no daily usage limit. Everything is processed inside your own browser, so the data you paste is never uploaded to a server.
How to use the Solar Panel Calculator
- Enter your figures in the input fields.
- The result updates as you type, together with the full working.
- Check the breakdown table to see exactly how the number was reached.
About the Solar Panel Calculator
The Solar Panel Calculator sizes a solar array from your monthly electricity use, local peak sun hours and panel rating, including realistic system losses. It runs as plain JavaScript inside the page, which means there is no upload step, no queue and no size limit imposed by a server — the only limit is your own device.
What people use it for
- Sizing a rooftop system from your own bill.
- Sanity-checking an installer’s proposal.
- Estimating roof space needed before committing.
Details
| Pakistan / India | ≈ 5 peak sun hours |
|---|---|
| Northern Europe | ≈ 3–3.5 |
| System losses | Typically 20% |
| A 550 W panel needs | ≈ 2.3 m² of roof |
The maths behind it
This tool uses Array size = daily kWh ÷ (peak sun hours × 0.8). The 0.8 accounts for inverter, heat, dust and wiring losses. Panels = array size ÷ panel rating. Every intermediate value is shown on screen, so the result can be checked by hand.
Peak sun hours is not daylight hours — it is the equivalent hours at full rated output, and it drops in winter exactly when use rises. Shading matters more than people expect: one shaded panel can pull down a whole string. Get a site survey before ordering.
Frequently asked questions
How many solar panels do I need for a 600 kWh month?
At five peak sun hours and 20% losses, about 5 kW of panels — roughly nine 550 W modules and about 21 m² of unshaded roof. Enter your own bill figure above.
Why not just divide my bill by the panel rating?
Because a panel almost never produces its rated output. The rating is measured under laboratory conditions; real output is reduced by heat, dust, wiring and inverter efficiency, which is what the 0.8 factor represents.
Do I need an account to use the Solar Panel Calculator?
There is no cost and no cap. The Solar Panel Calculator is not a demo of a paid product, so nothing is held back or watermarked.
Is the Solar Panel Calculator safe to use with private information?
No. The Solar Panel Calculator runs entirely in your browser using JavaScript. Nothing is transmitted, logged or stored, which you can verify yourself in the Network tab of your browser's developer tools.
What formula does the Solar Panel Calculator use?
It uses Array size = daily kWh ÷ (peak sun hours × 0.8). The 0.8 accounts for inverter, heat, dust and wiring losses. Panels = array size ÷ panel rating. The full working is printed under the result, so you can follow every step rather than trusting a black box.
What is the Solar Panel Calculator used for?
Typical uses: sizing a rooftop system from your own bill. Sanity-checking an installer’s proposal. Estimating roof space needed before committing. It is built for exactly those cases rather than being a general-purpose tool with this bolted on.
What do people usually get wrong here?
Peak sun hours is not daylight hours — it is the equivalent hours at full rated output, and it drops in winter exactly when use rises. Shading matters more than people expect: one shaded panel can pull down a whole string. Get a site survey before ordering.
What are the key numbers for the Solar Panel Calculator?
Pakistan / India is ≈ 5 peak sun hours. Northern Europe is ≈ 3–3.5. System losses is Typically 20%. These are printed on the page itself, so you do not have to take them on trust.
How precise is the result?
The calculation runs in double precision and the result is shown to ten significant figures, so converting a value and converting it back returns the original. What is displayed is rounded for readability; what is copied is not.
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