What would solar panels, a battery, or both have saved you? This replays your own half-hourly electricity use from Octopus Energy, with the solar your panels would have made and the real prices of each tariff, over a year you choose.
How it works. It fetches your half-hourly electricity readings from Octopus Energy for the twelve months you choose, finds your location from your postcode, and works out what panels like yours would have generated there in each half hour. The rest is maths.
Prices. Each tariff uses its real half-hourly prices for those months, from Octopus, including VAT (Direct Debit). Agile, Cosy and Go use whichever version was on sale at the time; Flexible Octopus follows the price cap. You can also set your own import and export prices.
Solar generation. A typical year for your location and panel angle from PVGIS, the European Commission's solar database. When PVGIS can't be reached, Open-Meteo's satellite-based estimate is used instead, scaled to match PVGIS.
Limitations. It replays a past year as if you had had solar or a battery. Nobody knows future prices, so the aim is to say: based on what happened, this is what you could have saved.
The battery model. The battery is dispatched with perfect foresight to save the most money on your tariff, so it shows the most a real battery could earn. The "skip trades worth less than" slider stops it trading for small gains, closer to how a real battery behaves. Octopus free-electricity sessions and Saving Sessions are not included.
Heat pump scenarios. If your account has gas readings, the calculator estimates your home's heat loss from your winter gas use and the local weather; you can also choose a heat loss. It then adds the measured electricity use of a matching heat pump from HeatPumpMonitor.org.
Your data. Your API key is used in memory to fetch your readings. It is not stored, logged or shared.