How to Use the Energy Bill Calculator in the UK

Understanding your energy bills can feel complicated, but an energy bill calculator helps estimate your electricity and gas costs based on your usage, tariff, and location.

It uses real info from Ofgem 2025, rates for your area, and what you read from your meter. This helps give a clear idea of your total energy costs.

By comparing results, you can easily compare energy prices across suppliers and find the most cost-efficient tariff for your household.

Try the energy bill calculator

What Is an Energy Bill Calculator and Why Do You Need One?

An energy bill calculator helps you figure out what you may have to pay your energy supplier. It uses your energy use, unit rate, standing charge, and payment method to do the calculation. The calculator changes your kilowatt hours (kWh) into an estimated bill, and it adds VAT to the total.

For 2025, the average UK household pays around £1,755 each year for dual fuel under the energy price cap set by Ofgem (October–December 2025).
This amount is based on paying by direct debit. It uses the standard variable tariff, with a usual household using about 2,700 kWh of electricity and 11,500 kWh of gas per year.

The calculator helps you if you use any of the big energy companies. This includes British Gas, OVO, EDF, E.ON Next, Scottish Power, and SO Energy. It works for people on fixed rate tariffs, variable rate tariffs, and also for those with a prepayment meter in Great Britain.

How Does the Energy Bill Calculator Work?

Example (Ofgem Oct–Dec 2025):

• The electricity unit rate is 26.35 p per kWh.
• The gas unit rate is 6.29 p per kWh.
• The standing charge each day, for each fuel, is 29.82 p. This is about £109 every year.

The calculator applies these automatically based on your postcode, tariff, and energy usage.

What Information Do You Need to Use the Energy Bill Calculator?

Step-by-Step Guide: How to Use the Energy Bill Calculator

The Free Price Compare calculator is easy to use. It takes you through seven simple steps. These steps are the same ones suppliers use to work out your utility bills.

Step 1 – Enter Your Postcode

Enter your postcode so the calculator identifies your energy region and the relevant distribution network operator.
Regional unit rates and standing charges vary; for example, homes in the South West often pay more than those in the North East.
Accurate postcode entry ensures the tool displays the right energy tariffs available in your area.

Step 2 – Select Your Address

After entering your postcode, choose your address from the list. This ensures correct local rates and helps the calculator detect your current or old supplier if available.
Address precision is especially useful if you have just moved into a new home, as it ensures the right standing charge and unit rate for both fuels.

Step 3 – Confirm Your Supplier and Tariff

Next, pick your energy supplier. For example, you can choose British Gas, OVO Energy, or E.ON Next. Then, choose your energy tariff.

• Standard Variable Tariff – the price can go up or down with the energy market, but there is a cap set by Ofgem.
• Fixed Rate Tariff – your rates stay the same for a set time.
• Prepayment Tariff – you pay as you use your energy with a prepayment meter.

This helps you set a starting point. You can use it to compare any new energy deals in the future.

Step 4 – Enter Your Energy Usage

Enter your yearly or monthly electricity usage and your gas usage in kWh.
If you don’t know your figures, the calculator can estimate based on typical consumption values:

• Electricity ≈ 2,700 kWh / year
• Gas ≈ 11,500 kWh / year

You can also import readings directly from a smart meter or add manual values.
The calculator multiplies your usage by the unit rate, adds the daily standing charge, and applies 5 % VAT.

Estimate your bills with the energy calculator

Step 5 – View Your Current Plan Cost

The calculator now shows your guess for how much your bill may be each month and for the year. It splits your bill into:

• Electricity cost
• Gas cost
• Standing charges
• VAT

Example (Ofgem 2025 typical household):

• The cost of electricity is about £711 each year.
• The gas bill is about £723 each year.
• The standing charges are close to £218.
• The total adds up to around £1,755 each year.

Step 6 – Compare Energy Deals

You will see a list of energy plans. They are sorted by the money you could save.
Each deal includes: supplier, tariff type, estimated annual cost, exit fee, payment method, and percentage of renewable energy.

Switching to a fixed tariff can protect against price rises, while a variable rate may fall if wholesale costs drop.
Results are compliant with the Energy Switch Guarantee, so your power and gas continue during the switch.

Find out your estimated annual energy cost

Step 7 – Complete Your Energy Switch

Pick the new supplier you want to go with. The new supplier will get in touch with your old supplier to close your old account. They will also ask you for your meter readings.

The switch usually takes about five working days. This is set by the Ofgem Confidence Code.

Your next bill will show your new tariff and payment terms.

Save More with Dual Fuel Energy Tariffs

Switch both gas and electricity in just 6 minutes and cut your bills.

Compare Dual Fuel Tariffs

How Does the Energy Calculator Adjust for Different Tariffs?

Standard Variable Tariff:
This is a type of variable tariff where the energy price is tied to the energy price cap. The price you pay can go up or down every three months. It changes when the market price changes. The standard variable tariff follows the rules of the energy price cap.

Fixed Rate Tariff:
This plan lets you keep the same rates for 12 to 24 months. If you leave early, there may be an exit fee. A fixed rate tariff helps people feel more sure about their bills.

Prepayment Meter:
Prepayment meter lets you pay before you use the energy. It often costs more for each kWh, and the standing charges that come with it are, in most cases, the same as other options.

Economy 7 / Smart Meter Tariffs:

Get lower price electricity at night. You put in your day and night smart meter readings apart to get the right numbers.

Why Does the Calculator Ask for Your Postcode?

Energy costs are not the same in every area. This is because different regions have their own local network charges.

Two homes using the same amount of energy can have different bills due solely to location.

How Do You Read Your Meter and Understand kWh?

Take both electricity (kWh) and gas (m³) readings. Subtract the previous reading from the current one to find usage.
If you have a smart meter, readings update automatically in your online account or app.

A kilowatt hour (kWh) measures one unit of energy — equivalent to using a 1,000-watt appliance for one hour.

How Do Payment Methods Affect Energy Costs?

Direct Debit: usually cheapest; spreads payments evenly and qualifies for lower rates.
Prepayment Meter: helps budgeting but has higher rates and daily standing charges.
Pay on Bill: flexible but costs more due to admin fees.

Payment choice can alter your total annual bill by £50–£120 depending on supplier and region.

What’s the Difference Between Gas and Electricity Costs?

While the price for each unit of electricity is high, using gas for heating helps to even out the overall cost.

How Do Property Type and EPC Rating Affect Your Bill?

Moving your EPC rating from D to C could help you save over £650 every year on utility bills.

What Are Daily Standing Charges and Why Do They Matter?

Every home in the UK has to pay a standing charge each day, even when there is no energy use. This fee is fixed. It helps pay for the things needed to keep your house linked to gas and electricity. These things include looking after power lines, checking meters, and giving customer service.

As of October to December 2025, Ofgem has set the standing charges as follows:

Together, these fees usually add up to about 10% to 15% of what a home pays for energy each year. The exact amount can change based on how much you use.

Even if you use no gas to heat your home in the summer, or you use little electricity in the day, you will still have to pay the standing charge. This is because the standing charge is there to keep your energy supply active and ready for you to use whenever you need it.

When you put your details into the energy bill calculator, the fixed costs are added to your total right away. The tool takes your daily standing charge for the billing time. It multiplies that charge by the number of days. Then, it adds this amount to your unit rate for how much energy you use.

For example, if you put in 11,500 kWh of gas and 2,700 kWh of electricity, the calculator will use the right standing charge for each type of fuel. This way, you get a total that shows your real costs. This helps you see your estimated bill match what suppliers charge, based on the energy price cap. You can look at your energy costs and get a clear idea of what you will pay before you compare energy prices or choose a new tariff.

How Does the Calculator Handle Decimal Places and Watts of Electricity?

The calculator gives you results with two decimal places. For example, you might see 2.45 kWh.

If you want to work out the cost of an appliance yourself: Watts × Hours ÷ 1,000 = kWh. Then, use your unit rate and multiply it by the kWh. After that, add the standing charge.

This shows how things you use every day, like appliances and light bulbs, can change your electricity cost.

What Happens When You Switch Energy Tariffs?

When you switch:

1. Your new supplier contacts your old supplier to close your account.
2. Final meter readings settle your old balance.
3. The Energy Switch Guarantee ensures no loss of supply.
4. Most switches complete within five working days.

Your new deal then starts automatically on the agreed date.

Compare energy prices to get the best energy tariff

Prepayment Meter Tariffs – Find Cheaper Options Today

Compare top-up tariffs in your area and cut your prepayment energy costs.

Find Cheaper Prepayment Tariffs

Benefits of Using the Energy Bill Calculator

• You get a clear view of your unit rate, standing charge, and VAT.
• See your total energy usage and the cost of your energy at any time.
• You can check different tariffs to find out about potential savings.
• Support for all payment methods and energy suppliers.
• Up-to-date price cap figures and regional rates.
• Easy access to new energy supplier choices and renewable energy tariffs.

FAQs About the Energy Bill Calculator