About WattPayback

WattPayback is a suite of home-energy calculators. The aim is simple: show the arithmetic behind solar and heating decisions, with every assumption editable and every formula printed out.

Installer sites often hide defaults that make payback look shorter. Here, region yield, self-consumption, degradation, export rates and the rest are inputs — not locked marketing choices.

This is physics and arithmetic, not professional advice. Use the tools to understand orders of magnitude, then get a site-specific survey before spending money.