Investment summary
10.7 years
Simple payback from year-one savings before electricity price inflation.
Verdict
Reasonable
Inflation-aware payback
9.1 years
25-year total return
£11,930
Total lifetime savings
£17,930
Indicative IRR
8.4%
10-year savings table
Net upfront cost: £6,000| Year | Generation | Annual savings | Cumulative |
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Methodology
How this solar return model is built
Year-one value comes from two income streams: electricity you use on site, which avoids imports at your electricity tariff, and exported electricity, which earns the selected SEG rate. The self-consumption slider lets you test how batteries, home occupancy, or flexible loads may improve on-site value.
Annual generation gradually falls according to the degradation assumption. Meanwhile, the avoided-import component rises with the assumed energy inflation rate. That means inflation-adjusted payback can be materially shorter than simple payback when electricity prices rise faster than zero.
The 25-year total return is calculated as lifetime savings minus net upfront cost after grants. The internal rate of return is an indicative IRR solved from the annual cash flow series and should be treated as a planning metric rather than formal financial advice.
This model does not include inverter replacement, maintenance, financing costs, tax effects, or opportunity cost of capital. For owner-occupiers, the main question is usually whether the installed price is low enough relative to yield and self-consumption to produce a strong long-term return.