What's behind a payback figure
Every solar proposal leads with a payback figure. Few explain what's behind it. The number is only as good as the assumptions underneath — and those assumptions are where projects quietly succeed or fail.
The variables that actually move payback
System cost per kW, your consumption profile, the share of generation you self-consume, and your tariff all matter more than which panel brand sits on the roof.
A payback figure without the assumptions behind it is a marketing number, not an engineering one.
1. Self-consumption rate
The percentage of generation you use on site is the single biggest lever. A system that exports half its output earns far less than one sized to be consumed where it's made.
2. The tariff you're escaping
Payback is really a comparison against what you'd otherwise pay the grid. A site on an expensive, peaky tariff pays back faster than one on a flat cheap rate.
3. The 25-year view
Payback marks the break-even year. The value is in the two decades after it, as grid prices rise and the asset keeps producing.