Why is my electricity bill so high?

1. Is the reading estimated?

Look for the word “estimated” next to the meter readings. If it is there, the bill is not a record of what you used — it is the supplier’s model of what you probably used, and estimates drift, sometimes badly.

Submit an actual reading. The period is rebilled against it. Do this before investigating anything else, because until it is done nobody can tell whether the bill is wrong or the estimate is.

2. Does the arithmetic check out?

Take your usage, unit rate and standing charge and work out what the bill should be. If it matches, the bill is correct and the question becomes why the usage is high — which is a different problem. If it does not match, you have something specific to raise.

Use the electricity cost calculator, and see how the sum works.

3. What is your overnight base load?

Read the meter last thing at night and again first thing, with nothing running that you would not expect. The difference, divided by the hours, is what your home draws constantly.

Under about 0.1 kW is unremarkable. Much above it means something substantial is running around the clock — and at 0.4 kW you are spending roughly £850 a year on whatever it is. Finding it is usually worth more than every other change combined. How to do it.

4. Is something electric heating when it should not be?

The usual suspects, in rough order of how often they turn out to be the answer:

• An immersion heater left on, or on a timer nobody set.
• A heated towel rail running all year.
• Underfloor heating in a bathroom, on a thermostat set high.
• A plug-in heater in a spare room or conservatory.
• Frost protection in a garage or outbuilding.

Each is easy to leave running for months without noticing, and each is expensive, because electric heat costs around four times what the same heat costs from gas.

5. Has something changed in the household?

Working from home a few days a week, a new appliance, a teenager, a hot tub, a car. These are real causes rather than faults, and they are worth quantifying rather than guessing at — a single appliance is rarely the whole story.

6. Are the rates the problem rather than the usage?

Check this last, not first. If your usage is unremarkable and the arithmetic matches, the remaining variable is what you pay per unit. That is a real cause, and it is the one with an answer that costs effort rather than money.

Use the tariff comparison, and take the standing charge and any exit fee into account — a lower unit rate on its own does not make a tariff cheaper.

What not to do

Do not buy anything until you know what the cause is. The most common outcome of this checklist is an estimated reading or an immersion heater, and neither is solved by a purchase.