How we calculate
The method behind every SolarCalcLab result, step by step.
Every SolarCalcLab result follows the same five steps. This page explains each one, so you know what a number means and where its limits are.
1. Your inputs
You enter values in the units you use: watts or kilowatts, feet or meters, AWG or mm². We convert units internally and show the converted values in the working, so nothing is hidden.
2. Location data
Tools that depend on sunlight use hourly irradiance and modeled yield from the European Commission’s PVGIS service, which covers most of the world, and from NREL’s PVWatts for the United States. Where a tool uses a typical figure instead of your exact location, it says so next to the result.
3. Open formula
Each calculator prints the formula it used and the same formula with your numbers substituted, so you can repeat the calculation by hand. The full method, symbols and worked examples sit below the tool.
4. Standards and limits
Electrical tools name the guidance they compare against, such as the voltage drop recommendations in the US National Electrical Code and BS 7671 in the United Kingdom. These comparisons are guidance only. Local code and a licensed electrician have the final say.
5. Sources and date
Every tool lists its sources and the date its data and method were last checked. When a tariff, rebate or rule changes, we update the tool and the date.
What our results do not do
- They are estimates for planning, not a design certificate or a quote.
- Unless a tool says otherwise, they ignore site details we cannot see, such as roof shading, cable bundling or local permit rules.
- Financial results use the rates you enter or the published averages we show. Your bill may differ.
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