All guides
Interactive guides to home energy
Four explainers that open the box on the technology in your house — heat pumps, solar panels, batteries — and let you test the numbers with your own prices. Plain language, no sales pitch.
How a heat pump works
Why a heat pump can deliver three times more heat than the electricity it uses — the refrigerant loop, step by step, with an interactive diagram.
Open the guide → 02Heat pump vs. gas boiler: the real savings
A calculator that compares running costs using your own gas and electricity prices, and shows the efficiency a heat pump needs to come out ahead.
Open the guide → 03How solar panels work
From photon to wall socket: the physics of a solar cell, the job of the inverter, and a calculator for what a roof like yours could generate.
Open the guide → 04Is a home battery worth it?
Simulate a day with and without a battery, see how quickly extra capacity stops paying, and calculate the one number that decides.
Open the guide →How these guides are made
Cutaway Guide explains the technology inside the modern home — the parts you normally never see — with interactive diagrams, simulators and calculators that run on your own numbers. Each guide starts from the physics and ends with a decision.
The models are deliberately simple, and their assumptions are written next to every tool. They are for understanding, not for quoting: real prices, roofs and tariffs vary, so check any decision against offers and bills from your own installer and supplier. Each guide shows the year it was last reviewed, and we revisit them regularly.
The site is independent. It is not affiliated with any manufacturer, installer or energy supplier, it carries no sponsored content, and it is funded by advertising. If you spot a mistake or want a topic explained, the About page says how to reach us.