When solar panels pay back: which factors to calculate

Payback depends on installation cost and the economic value of its energy. Two systems with the same capacity can produce different financial results. A useful comparison separates production, self-consumption and exports, making assumptions visible.

Use verifiable production and consumption

Enter an annual production estimate from your system design and consumption from bills. Simuily does not fetch local irradiation or know roof orientation or shading. Modelled self-consumption is the smaller of annual consumption and production × self-consumption share. An annual comparison does not reproduce hourly operation or detailed battery behaviour.

Separate avoided costs and export revenue

Avoided cost = self-consumed energy × purchase price. Export revenue = remaining production × entered export price. Annual net benefit = both amounts − maintenance. Do not value exports at the purchase price if your contract compensates them differently. Example prices are hypothetical, not current tariffs, and fixed bill charges do not necessarily disappear.

Read payback and the study horizon

Net investment = initial cost − entered incentives. The model does not look up grants or guarantee eligibility. With constant positive annual benefits, simple payback = net investment / annual benefit. With degradation, annual benefits are accumulated and the recovery-year fraction is estimated. If the investment is not recovered within the horizon, that limitation is shown rather than an invented date.

Compare scenarios without promising returns

Test lower output, different prices and higher maintenance. Cumulative balance is not net present value: cash flows are not discounted and financing, taxes, inverter or battery replacements are not automatically included. Consider these costs in further scenarios and review the technical quote before deciding.

Hypothetical example, not a forecast

The amounts are invented examples. They are not current prices or personalised recommendations.

Example inputs

Approximate results

A common question

Does higher self-consumption always mean more saving?

It depends on avoided purchase prices, export compensation and the cost of achieving it. A battery adds costs to consider separately.

Try these inputs and compare different assumptions in the calculator.

Electricity cost calculator