Calculators
Plan with your own numbers
Each calculator uses the same open model: a representative day per month, simulated in quarter-hour steps, with every assumption written out beneath it. Nothing you enter leaves your browser.
Solar yield and payback calculator
Annual yield, self-consumption, savings and payback for your roof.
Open calculator
Home battery planner
How self-sufficiency grows with every extra kilowatt hour of storage.
Open calculator
Heat pump running cost calculator
Electricity use, running cost and CO₂ compared with a gas boiler.
Open calculator
EV charging time and cost calculator
Charging time, energy from the wall, cost and range added.
Open calculator
What the calculators can and cannot do
They are made for the early questions: is the roof worth it, how large should the battery be, will a heat pump cost more or less than gas, how long does the car take to charge. They do not replace a site visit, a shade analysis or a heat load calculation, and they do not know your tariff better than your bill does. Use them to ask better questions when the offers arrive.