How We Calculate Energy Costs

For every tariff we list, the annual cost is calculated as:

annual cost = (electricity unit rate × elec kWh)
            + (electricity standing charge × 365)
            + (gas unit rate × gas kWh)
            + (gas standing charge × 365)

Unit rates and standing charges come from each supplier's published rates — via a daily API feed for Octopus tariffs and dated, hand-checked figures for other suppliers — and we show the resulting annual cost alongside the assumptions used.

Unless you give us your own usage, we use Ofgem's Typical Domestic Consumption Values (TDCV) for a medium dual-fuel household:

• Electricity: 2,500 kWh per year (single-rate)
• Gas: 9,500 kWh per year
• Multi-register electricity (e.g. Economy 7): 3,400 kWh per year
• Payment method: Direct debit (most common in the UK)
• Region: National average — regional variations shown separately on the regional pricing pages

Smaller households (1–2 people) typically use ~1,800 kWh elec / 8,000 kWh gas; larger households (4+) typically use ~4,100 kWh elec / 17,000 kWh gas. Use our postcode estimator to refine for your home.

• Tariff data: Octopus Energy rates are pulled daily from Octopus's public API. Other suppliers' rates come from their published rate cards; where a figure is live we label it, otherwise it is a dated, hand-checked figure.
• Price cap: Ofgem's quarterly default tariff cap announcements, detected by an automated daily check of Ofgem's pages and confirmed by a person before being labelled verified. Stored in one central record used across PowerGuardian. The current record is £1,862 for Q3 2026 (1 Jul – 30 Sep 2026).
• Market context: daily monitoring of Ofgem, DESNZ, NESO, Elexon and UK energy trade press. We do not operate a direct exchange or wholesale data feed, and we don't claim to.
• Policy & statistics: Department for Energy Security & Net Zero (DESNZ).

We do not currently publish a forward price forecast. Our outlook pages show the price caps Ofgem has actually announced, and say plainly that no estimate is published for the quarters beyond them.

What does operate, and can be demonstrated:

1. A daily check of Ofgem's own price cap pages. When a new cap is announced, the annual figure, unit rates and standing charges are read from the publication and stored with its publication date. Anything that does not parse cleanly is held back for a person to check.
2. A separate human confirmation step. A figure is only labelled as confirmed once someone has checked it against the Ofgem publication. Until then the page says it was read automatically and has not been checked by hand.
3. Dates kept apart. The source publication date, the data period, the automated refresh date and the human review date are recorded and shown separately. An automated job never advances a human review date.

Earlier quarterly estimates were withdrawn in September 2026 because their inputs and calculations were not recorded, so nobody could reproduce or defend them. Forward estimates will only return if they can be calculated from a recorded wholesale price input using Ofgem's published cap methodology, or licensed from a published forecast we are permitted to republish. Confidence labels will not return without a documented basis for them.