Solar Panel Payback Calculator

Estimate a solar-panel system’s simple payback using installation cost, generation, self-use and export payments. See annual benefits and how they add up under your chosen assumptions.

How to use Solar Panel Payback Calculator

1. Choose the currency used for results. 2. Use generation and household consumption from a quote or measured data. Enter the share of generation used at home, the import price avoided and the export payment received. 3. Change a value to update the results, or select Calculate. Review the chart and notes with the total. 4. Use Copy results, Share results or Download result graphic to keep the answer. Shared links include your figures. 5. Reset restores the editable example inputs.

Why use this tool?

Electricity used at home and electricity exported can be worth different amounts. A solar payback calculation that prices every generated kWh at the import tariff can overstate the benefit. This tool values those two parts separately. The result is a simple payback, with an annual allowance for maintenance or future components. It does not forecast sunlight, a roof’s output or when electricity is used. The self-use assumption should reflect how much generation can actually replace imported electricity, including any battery arrangement in the figures you have chosen.

How the calculation works

Self-used kWh = annual generation × self-use percentage ÷ 100. Exported kWh is the remainder. Annual net benefit = self-used kWh × avoided import price + exported kWh × export rate − annual maintenance allowance. Net upfront cost = installation cost − grant or discount. Simple payback = net upfront cost ÷ positive annual net benefit. Self-used generation cannot exceed the entered household consumption. The projection repeats the entered annual benefit. It excludes tariff changes, generation degradation, financing and investment opportunity cost, and includes future component costs only through your allowance.

Example

With 4,000 kWh generated, 50% self-use, an illustrative £0.25 import rate, £0.08 export rate and £80 annual allowance, net benefit is £500 + £160 − £80 = £580 a year. A £6,000 net installation cost has simple payback of about 10.34 years.

Practical tip

Try a lower self-use percentage and a lower export rate to see how sensitive the payback is. Keep battery purchase cost and its effect on self-use consistent rather than adding its benefit without its cost.