How to estimate your energy use

The energy price cap

When we talk about the energy price cap we often talked about it as a single headline figure based on a “typical” household. Energy quotes are often presented in the same way. But the price cap does not limit your total bill.

Instead, the energy price cap limits:

the unit rate (what you pay per kWh of gas or electricity), and

the standing charge (the daily fixed cost).

It only applies to households on variable or default tariffs. If you’re on a fixed deal, the cap does not apply.

Your total bill still depends on how much energy you use.

Your usage matters

No matter what tariff you’re on, if you know:

Your unit rates, and

your annual gas and electricity usage,

You can get a much more accurate idea of what your energy will actually cost.

This is especially useful when:

comparing tariffs, as suppliers split costs differently between unit rates and standing charges

checking whether your direct debit is realistic

Do you know your energy usage?

If you’ve recently moved in, or don’t have past bills, you can estimate your usage using national averages.

Price comparison sites usually ask whether you are a low, medium or high user:

Low users: small flats or houses, 1–2 occupants

Medium users: medium-sized homes (2–3 bedrooms), 2–3 occupants

High users: larger homes (4+ bedrooms), 4–5 occupants

The energy price cap is based on a medium user. But households vary widely. Usage depends on:

how warm you keep your home

how often someone is at home

insulation and energy efficiency

Because of this, average figures are only a guide. Your real usage will always give a more accurate picture.

Why estimates can cause problems

When suppliers rely on estimates, your bills can be:

overestimated, leaving you with large credit balances

underestimated, leading to debt

This often means your direct debit doesn’t match what you’re actually using.

Your energy account usually shows your supplier’s estimate of your annual usage. This is based on past data and may not reflect changes in how you live now.

How often does the price cap change?

The energy price cap is updated every three months.
Check the latest price cap update to see current rates.

How to find your actual energy usage

If you’ve been with your supplier for a while and submit regular meter readings (or have a smart meter), your data should be fairly accurate.

You can:

check your online account or app

look at your annual statement

use smart meter data for a detailed breakdown

How to calculate your annual usage yourself

To find your actual usage over the last 12 months:

Find two meter readings roughly a year apart
(for example, 15 August 2025 and 15 August 2026).

Subtract last year’s reading from this year’s reading.

This gives you the exact number of units you’ve used in a year.

Working out electricity costs

Electricity is measured in kilowatt hours (kWh).

Multiply your annual kWh usage by your unit rate
(for many households this is around 26p per kWh)

Add your standing charge × 365 days

This gives you a much more accurate annual cost.

Working out gas usage and costs

Gas meters measure volume, not kWh, so a conversion is needed.

If your reading is in cubic feet, first multiply by 2.83
(skip this step if your meter is already in cubic metres).

Then:

Multiply by 1.02264

Multiply by the calorific value (shown on your bill)

Divide by 3.6 to get kWh

Once you have kWh:

multiply by your gas unit rate (often around 6p per kWh)

add your standing charge × 365

Your energy bill will show the exact formula your supplier uses.

Working out the cost of appliances

If you know an appliance’s wattage, you can estimate how much it costs to run.

Example:

Washing machine = 2,000 watts (2kW)

Run for 1 hour = 2kWh used

At 26p per kWh → 52p per hour

You can find wattage on the back or base of most appliances.

For more examples, see our guide on appliance running costs.

Get help

If you need advice about your situation, we can help for free.

• Email: info@youthlegal.org.uk
• Phone: 020 3195 1906 (Mon to Fri, 10am to 6pm)
• Contact form: youthlegal.org.uk/contact-us

All our advice is free and confidential.