Smart Home Energy How it works
The Tariff Checker has one job: tell you whether switching to a time-of-use tariff would actually save you money — for your specific setup.
Three steps
- We pull the real ratesin daily from supplier APIs where they're available. For other suppliers we maintain a manual rate table, reviewed each quarter on price-cap dates (1 Jan / 1 Apr / 1 Jul / 1 Oct).
- We model your usage depending on what you give us:
- Estimate— Ofgem's published average for your household size, plus the kWh implied by your equipment (EV mileage and efficiency, heat-pump size and insulation, etc.).
- Your number — typed annual kWh, a CSV from your supplier portal, or bills we read by OCR.
- Smart meter— your last 12 months of half-hourly readings priced against each tariff's actual price for that exact 30-minute slot. No modelling, no shifting assumptions — just real consumption × real prices, showing you exactly what you would have saved on a different tariff.
- We rank honestly.The top three recommendations are the ones with the biggest annual saving for your setup. If your current tariff is already the best fit, we'll tell you to stay put.
Once the calculation runs, every input and assumption it used is exposed on the Results page and editable inline. Tweak your annual usage, EV efficiency, charging pattern, the share of base-home use you can shift to off-peak — anything that doesn't match your reality — and the numbers recalculate live.
What we don't do
- Hide tariffs from suppliers we don't have deals with.
- Take sponsorship money to promote one tariff over another.
- Recommend tariffs you're not eligible for (e.g. Octopus Intelligent Go without a compatible smart charger).
- Double-count your consumption — EV, heat-pump, and base-home kWh are kept separate so the maths is auditable.
When the numbers might shift
- The modelled tiers assume a typical pattern of when you use electricity. If your cooking, dishwashing or laundry runs mostly through the 4–7pm peak on a tariff that surcharges peak (e.g. Octopus Cosy), our savings figure might be slightly optimistic — but you can adjust how much of your usage is shiftable to cheaper times.
- Rates change. We refresh daily but there can be a lag — the supplier's own page is the source of truth.
Want exact numbers?
Connect your smart meter on the About your usage step. We read your half-hourly consumption directly and the modelling drops out — you get a saving figure based on real kWh × real prices. Currently works for Octopus customers; other suppliers in progress.
You can also read how we make money and why we're independent.