Direct debit checker: methodology
Where your data goes
Nowhere. Every figure is worked out in your browser and nothing you enter is sent to us or stored. When you arrive from one of the meter analysers, your yearly usage is passed in the part of the address after the #, which browsers never send to a server.
Walking the account forward
The checker starts from today’s balance and steps through the next twelve months a day at a time. Each day costs that day’s share of your year’s energy at that day’s prices, plus the standing charges. Your payment lands on its day each month. The result is your balance on every day of the year ahead, not just at the end of it, which is what shows a winter dip.
How your use spreads across the year
Electricity follows the monthly pattern of three million UK homes from the Faraday dataset, the same one the smart meter analyser uses: a January day uses +9.0% against the average day, a June day −9.1%. Gas follows a heating-season pattern, the same one the tariff checker uses: about 16% of a year’s gas in January and 2.5% in July. Homes heated by electricity, or with unusually high hot water use, swing differently, so treat the month-by-month figures as a guide and the yearly total as the firmer number.
| Month | Electricity, a day against average | Share of a year’s gas |
|---|---|---|
| January | +9.0% | 16.2% |
| February | +8.4% | 14.1% |
| March | +4.2% | 12.1% |
| April | −1.0% | 8.1% |
| May | −6.2% | 5.1% |
| June | −9.1% | 3.0% |
| July | −9.0% | 2.5% |
| August | −8.1% | 2.5% |
| September | −4.5% | 3.5% |
| October | +1.2% | 7.1% |
| November | +6.1% | 11.1% |
| December | +9.5% | 14.6% |
Prices
A fixed tariff keeps its prices for the year. A variable tariff follows the price cap under the scenario you choose; each step multiplies the unit rates and standing charges from its start date. The scenarios, as at 23 October 2026:
- No change. The cap stays where it is for the whole year.
- Lower forecast. Up 16% in January, Cornwall Insight’s forecast of 30 September, the lowest published; then down 0.5% in April and 7.8% in July. Source: Cornwall Insight, 30 September 2026.
- Supplier forecasts. Up 26% in January, the average of British Gas, EDF and E.ON Next forecasts on 21 October; then down 0.5% in April and 7.8% in July. Source: Uswitch, supplier average as of 21 October 2026.
Electricity in Great Britain is zero-rated for VAT until 31 March 2027. The checker takes the prices you enter as today’s and adds the 5% back from the day after, on fixed tariffs too: VAT is passed through whatever the tariff. Gas VAT stays at 5% throughout.
The two payments
Break-even is the payment that brings your balance back to £0 a year from today: the year’s energy, less today’s credit (or plus today’s debt), divided by the number of payments in the year. It is what most suppliers aim for. Starting in autumn, it means owing money for part of the winter and clawing it back over the summer.
Never in debt is the smallest payment that keeps your balance at or above £0 on every day of the year. Your balance on any day is today’s balance, plus your payment times the payments made so far, minus what you have used so far, so the payment has to be at least (used so far − today’s balance) ÷ payments so far on every day. We take the largest of those. The days before your first payment can’t be helped by any payment, and the page says so if your balance dips below £0 then.
Credit you can safely take back is the lowest your balance reaches over the year at your current payment, if that stays above £0. Take back more and you would owe money at that low point.
What it doesn’t do
- Weather. A cold winter uses more than the typical pattern, a mild one less.
- Changes in how you live: a new baby, an electric car, working from home. Adjust your yearly usage for those.
- Prices further out than the scenarios. A fix ending during the year is treated as fixed for all of it.