How Our Comparison Works

Our energy price comparison calculator is wholly owned and managed by us and our team based in the UK. It uses information about your current energy supply arrangements to identify or calculate your average annual energy usage. It then uses this annual usage figure to calculate comparative quotes for all available products available to you so you can easily compare these with your current gas and electricity tariff. All calculations are fully impartial and are calculated on a true like-for-like basis.

A bit about our history

The Energy Shop calculator was the first ever price comparison service to be accredited under the energywatch Code for energy price comparison sites (now the Ofgem Confidence Code) back in 2003. We have remained accredited by the Confidence Code since we first launched almost 20 years ago. This means that we have consistently passed strict tests that confirm that the service we offer is comprehensive in our coverage of energy suppliers and energy tariffs, accurate in the presentation of our results, and totally impartial.

The detail - how we actually compare!

From your address we identify the region of the country in which you live and filter out the range of tariffs available to you because energy suppliers have different prices in different regions. NOTE: There are 14 different regions in the UK known as PES regions each carrying their own set of rates/prices for any given tariff. Imagine the costs to provide power in the Scottish Highlands (long cables to a few spread out properties) compared to the costs to provide power in London to thousands of properties in one block of flats.

From the details of you current energy supplier, current energy tariff, current payment method and current consumption, we calculate the annual bill that you will pay with your current supplier based on their latest prices. We then compare this to the bills that you would pay with all the other energy suppliers and prices available to you in your area based upon your payment and tariff preferences.

If you do not know your annual usage in kilowatt hours, but know your approximate annual gas bill and / or your electricity bill, then we will use the bill information you give us to calculate your annual energy usage based upon your current energy supplier's latest prices. From the calculated usage figure, we then compare the bills that you will pay with your current supplier with the energy bills that you would pay with the other energy suppliers and energy tariffs available to you in your area based upon your payment and tariff preferences.

The estimated savings are calculated by subtracting the annual cost of the new tariff from the cost with your current energy supplier and tariff.


Current Annual Gas Usage: 12,000kwh

Current Annual Electricity Usage: 2,900kwh

First, let's look at the current gas bill.

Current Standing Charge = 20p per day

Annual Standing Charge = 20p X 365-days = £73.00

Current Gas Unit Rate = 2.5p per kilowatt hour (kwh)

Current Gas Usage Cost = 2.5p p/kwh X 12,000kwh = £300.00

TOTAL GAS COST = £73.00 + £300.00 = £373.00

Next, let's look at the current electricity bill.

Current Standing Charge = 20p per day

Annual Standing Charge = 20p X 365-days = £73.00

Current Electricity Unit Rate = 18.5p per kilowatt hour (kwh)

Current Electricity Usage Cost = 2.5p p/kwh X 12,000kwh = £536.50

TOTAL ELECTRICITY COST = £73.00 + £536.50 = £609.50

TOTAL BILL = £373.00 (Gas) + £609.50 (Electricity) = £982.50.

So, this is your current energy bill breakdown and enables us to see that you are currently spending £982.50 a year on your gas and electricity bills.

Next up, we do the same calculation using your existing usage, to see what the cost will be for all of the currently available energy tariffs for your postcode.

The options available to you, in order of price with the cheapest at the top, might be:

Option 1 = £900.00

Option 2 = £910.00

Option 3 = £935.00

Using your existing cost of £982.50, this would then show that the above options would give you the following annual savings:

Option 1 = £982.50 (your current cost) - £900.00 (the cheapest option) = £82.50 annual saving.

Option 2 = as above = £72.50 annual saving.

Option 3 = as above = £47.50 annual saving.


The default presentation of the results is shown strictly in the order of lowest cost (highest saving) first. You are then able to narrow your results by selecting the tariff types you are interested in e.g. fixed/variable tariff, paper/paperless billing etc... You can also choose to sort your results by factors other than price (for example by length of fixed period or tariffs with no exit penalty) and decide which energy payment options you want to see.

Please note that you can opt to filter tariffs based on the features and preferences you require. However, if you choose to do this to refine your search, then you will only see those tariffs that match your criteria. In this case you may no longer see the cheapest energy tariffs available to you.

Energy usage - best results!

For the most accurate energy comparison it is best to enter your annual gas and electricity usage in kilowatt hours. You can obtain this information by adding the usage figures from your last four quarterly gas bills and electricity bills. Alternatively, you can get this information by calling your current energy supplier.

If you do not know, or cannot obtain, details of your usage or annual bill, then we suggest that you use one of the usage profiles shown below. These profiles have been compiled by energy watch, the gas and electricity watchdog, and represent the current industry standard for domestic energy usage profiles.

Profile Gas Standard Rate Electricity Economy 7 Electricity (Day Units) Economy 7 Electricity (Night Units)
Low 8,000 kWh 1,650 kWh 2,400 kWh 1,800 kWh (42.0%)
Medium 12,000 kWh 3,300 kWh 4,200 kWh 2,900 kWh (42.0%)
High 17,000 kWh 4,950 kWh 7,100 kWh 4,300 kWh (42.0%)

The Calculation details explained

Our calculator uses the most up-to-date energy prices available and the website is often updated within hours of a price increase being announced. This means that the calculator is always using the most up to date information for comparison purposes. To check exactly which tariff have been included in the comparison please check the Tariff Updates page.

The calculator looks at several variables when calculating the annual bill for each tariff. It then works out how much you could save by switching from your current energy supplier to each available tariff. The variables used are:

Standing Charges. This is where the supplier charges a fixed daily amount irrespective of the amount of energy that you use. This does not apply to all energy tariffs.

Unit Rates - These are the rates that you pay for each unit of gas and electricity that you use. In working out which unit rates to apply, we take into consideration consumption thresholds. This is where different unit charges apply depending upon the amount of energy that you use in a given period. Typically, you will pay a higher unit rate for the first block of units used in a given period, and a lower rate for the second and subsequent blocks of units used thereafter.

Discounts - We take into consideration all recurring discounts or charges that are automatically applied to the given tariff.


In determining which discounts to include, we work on the underlying principal that only recurring cash discounts (or charges) that are automatically applied to tariffs each year are included in our calculations. Introductory or one-off discounts are not included, nor are charges that may be incurred if a plan is cancelled or altered. If there is a one-off incentive for signing up to a particular product this will be shown in the special offers column of the results table. Were a tariff offers non-cash incentives we show details of the particular offer separately, but we do not put a cash value on any such incentives. Contributions made to charity are also not included in the calculated annual bill.

Discounts we include:

- Dual fuel discounts

- Direct Debit discounts (and any other discounts that may be applicable to a chosen payment method).

- Paperless billing discounts

- Online discount where customers obtain an ongoing discount for signing up online or agreeing to manage their account online

- Fixed charges where, for example, applying for a tariff also requires paying an ongoing monthly membership fee.

Historic plans

Our calculator includes plans that a customer may currently be signed up to, but which may no longer be available for new customers. These tariffs are sometimes called historic tariffs. Examples include Fixed Price or Capped Price energy deals that an energy supplier previously offered, but which has now withdrawn from the market. We include these in our database so that you can compare these tariffs with other deals in the marketplace. However as they are not available to new customers, they are not included in the results table. The list of such that tariffs we allow for comparison purposes is extensive but not exhaustive. Because many of these prices are no longer published, we cannot guarantee that we can include them all.

Non-Standard Meters

We do not currently provide comparisons for non-Standard Meters, for example Economy 9 or Economy 10.

Assumptions made

The main assumptions made are listed below and are applied consistently across all calculations. We assume that:

- You are a domestic customer and that the gas supply and electricity supply to your property is used wholly or mainly for domestic purposes.

- You already have an existing gas supply and / or electricity supply to your property. If you do not yet have a supply you will need to get a new connection first.

- Your gas connection is connected to the main national gas distribution network in the UK. Our calculator does not yet cover homes connected to Independent Gas Transporter (IGT) networks.

- All savings estimates are based on your current consumption. This implies that your annual usage will not change materially from year to year. If you believe that there is a good reason why your usage will change, upwards or downwards, then you should factor this into the estimates that you provide to us.

- The usage figures or energy bill figures that you input into our calculator accurately reflect your energy usage.

- You have been on your current tariff for the last 12 months as this is the tariff that has been used to calculate your annual savings.

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Ofgem Confidence Code
Fully accredited by Ofgem since 2003