What could you actually save?

The calculator below gives a range, not a single number, on purpose. Solar economics depend on so many variables — weather, tariff, household behaviour, export rate — that any single-figure estimate is misleading. We err toward honesty even if it makes the answer less satisfying.

Before the numbers, here's the first big variable: where you live. UK yield varies by roughly 40% between the sunniest South West and the least-sunny far North of Scotland.