The five numbers that matter
- Meter readings: 'actual' means read from your meter; 'estimated' means guessed. Estimated readings are the single biggest cause of wrong bills.
- Unit rate (p/kWh): what you pay per unit of energy. Gas and electricity have different rates — check both.
- Standing charge (p/day): the fixed daily fee you pay regardless of usage. Multiply by 365 to see its yearly cost — it's bigger than most people think.
- Tariff name: confirms which deal you're on and when it ends. If it says 'standard variable', you're probably overpaying.
- Usage in kWh: how much you actually used. Compare it with the same period last year to see whether a higher bill is usage or price.
Estimated bills: the quiet rip-off
When your supplier doesn't have a reading, it guesses — and the guess is rarely in your favour. A high estimate means you overpay now (you'll get it back eventually, but they've had your money). A low estimate is worse: you underpay for months, then get a catch-up bill for hundreds of pounds. The fix is free and takes a minute: photograph your meters and submit the readings every month, or get a smart meter and never think about it again.
Spotting a wrong bill
- Readings going backwards or jumping impossibly between bills — the meter serial number may be mismatched.
- A tariff name you don't recognise, or a unit rate higher than the one you agreed.
- Two bills covering overlapping dates, or a 'catch-up' bill stretching back many months (suppliers generally can't bill you for energy used more than 12 months ago if it was their fault).
- Direct Debit set far above your actual usage — suppliers must justify the amount and review it fairly.
What to do if it's wrong
Contact your supplier with your own meter readings and photos. If they won't fix it, escalate to a formal complaint — and if that's unresolved after 8 weeks, the Energy Ombudsman can step in for free. Keep copies of everything.
Frequently asked questions
What should I check first on my energy bill?
Three things: that the meter readings are actual (not estimated), that you're on the tariff you think you're on, and that the unit rate and standing charge match what you signed up for. Those three catch the vast majority of billing errors.
Why is my bill estimated and does it matter?
Suppliers estimate when they don't have a recent reading. Estimates are frequently wrong — too high and you overpay, too low and you build up surprise debt. Send a reading every month and the problem disappears.
What is a kWh on my energy bill?
A kilowatt-hour: the unit you're billed for. A typical UK home uses around 2,700 kWh of electricity and 11,500 kWh of gas a year. Your bill multiplies your kWh by your unit rate, then adds the standing charge.
My bill suddenly jumped — what should I do?
First check for estimated readings and whether a fixed deal just ended (rolling you onto the expensive standard tariff). Then compare your usage in kWh with the same period last year — if usage is similar but cost is up, it's the tariff, and it's time to switch.
Keep reading
Related: why the standing charge deserves as much attention as the unit rate.