Calculating your panels needed is straightforward once you know the Solar Panel formula and what each input means. This guide explains the method in plain language, walks through a manual calculation, and gives worked examples you can follow — then you can do it instantly with the Solar Panel Calculator.
What is Solar Panel?
The Solar Panel calculation tells you your panels needed from a few simple inputs. The figure you are solving for here is the panels needed.
The Solar Panel formula
This calculation combines several inputs through a multi-step method rather than a single one-line formula. Enter the values below and the calculator resolves each step in order. The inputs it needs are:
- Daily energy need — a value measured in kWh. Example: 10 kWh.
- Peak sun hours per day — a value measured in hours. Example: 5 hours.
- Panel wattage — a value measured in W. Example: 400 W.
How to calculate it step by step
- Write down the daily energy need (for example, 10 kWh).
- Write down the peak sun hours per day (for example, 5 hours).
- Write down the panel wattage (for example, 400 W).
- Apply the formula above to get your panels needed.
- Double-check the result with the Solar Panel Calculator.
Worked examples
Example 1
| Input / Output | Value |
|---|---|
| Daily energy need | 10 kWh |
| Peak sun hours per day | 5 hours |
| Panel wattage | 400 W |
| Panels needed | 5 |
| System size (kW) | 2.00 |
With daily energy need of 10 kWh, peak sun hours per day of 5 hours and panel wattage of 400 W, the panels needed works out to 5.
Example 2
With daily energy need of 20 kWh, peak sun hours per day of 5 hours and panel wattage of 400 W, the panels needed works out to 10.
| Result | Value |
|---|---|
| Panels needed | 10 |
| System size (kW) | 4.00 |
Example 3
With daily energy need of 5 kWh, peak sun hours per day of 5 hours and panel wattage of 400 W, the panels needed works out to 3.
| Result | Value |
|---|---|
| Panels needed | 3 |
| System size (kW) | 1.20 |
Tips for an accurate result
- Keep your units consistent — mixing, say, months with years or grams with kilograms is the most common source of error.
- Round only at the very end. Rounding inputs early can shift the final answer noticeably.
- Re-run the numbers whenever an input changes, rather than estimating from an old result.
Prefer not to do the maths by hand? — the Solar Panel Calculator does it instantly, for free, with the formula and a worked example built in.
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Continue exploring energy calculators with these tools: Generator Fuel Consumption Calculator, Solar Savings Calculator, Solar Payback Period Calculator, Generator Size Calculator, Inverter Size Calculator.