In Britain’s energy market, suppliers compete on price and service to win customers. In setting their prices, suppliers will seek to cover their costs and to make a profit. They face pressure to keep their prices and costs down, or else risk losing customers to their rivals.
We have a role providing impartial and authoritative data about the energy market. As part of this, we publish information about the prices that households pay for their energy, the profits suppliers make and the trends in the industry costs that suppliers face. This helps to improve transparency around trends in prices, and what may be driving them.
We are also working to facilitate a more competitive, dynamic energy market, with more engaged consumers. Over time, we expect the changes we make to the retail markets to increase the competitive pressure that suppliers face, and so help to keep energy prices down.
In the charts below you can view recent trends in prices for domestic customers split by tariff type and payment method, and trends in suppliers’ domestic pre-tax profit margins. Select the 'more information' tab in the chart for a summary of the latest trends and details of the methodology used.
You can find further information on trends in prices and profits in our reports on the retail and wholesale energy markets, and on our page Understanding the profits of the large energy suppliers.
To provide insight into the most recent developments in the costs suppliers face, we publish a Supplier Cost Index.
The index tracks ongoing trends in wholesale costs, network costs and the charges to suppliers associated with government programmes that are designed to, for example, help deliver low carbon electricity and energy efficient homes, and provide direct financial support to the fuel poor.
Note that while the index gives insight into current and future cost pressures, it is neither able nor intended to predict what prices suppliers will set or when these will change. The costs that individual suppliers incur in supplying their customers may vary significantly from the index. For example, while the index reflects the level of wholesale prices in the month prior to the update, some companies may buy energy for their customers over an extended period of time to smooth their costs.
Information on suppliers’ realised costs is available in the financial statements published by the six large energy suppliers. See Understanding the profits of the large energy suppliers.
Supplier Cost Index
Select a chart for our estimates of the latest trends in the cost index, and what is behind these.
Summary: May 2018
- In the three months (between 1 February 2018 and 1 May 2018) the index increased by 5.3%, driven primarily by increases in wholesale gas and electricity costs. There was also an increase in the costs of government obligations related to supplying electricity.
- Overall, the Supplier Cost Index (dual fuel) increased by 14.1% between 1 May 2017 and 1 May 2018.
- The 12 month increase was primarily driven by increases in wholesale gas and electricity costs.
- The index starts in January 2015. Costs fell during 2015 and early 2016, with much larger reductions for gas than electricity. By the 1 May 2018, the dual fuel index is 9.7% above its level at the start of 2015. The electricity index is 19.7% higher, while the gas index is 0.1% higher.
- We calculate the Supplier Cost Index by estimating trends in network charges, wholesale prices and the charges to suppliers associated with government programmes (note that in some cases, these government charges only apply to large and medium-sized suppliers).
- These estimates are then combined with information on the relative scale of each of these categories of cost to calculate the trend in the overall Supplier Cost Index. The weights given to each category of costs are based on financial statements from the six large suppliers, and are as follows:
- wholesale electricity: 26.7%
- wholesale gas: 35.9%
- networks electricity: 15.4%
- networks gas: 14.4%
- government obligations electricity: 6.7%
- government obligations gas: 1.0%
- The index reflects estimated expected annual costs, covering the 12 months from the time of each update, based on the best information available at the time. So, for example, the value of the index for May 2018 will reflect estimated costs for the period 1 May 2018 to 30 April 2019, expressed relative to estimated expected annual costs as of the base period (1 January 2015 to 31 December 2015).
- The estimates in the index are forward-looking, they therefore rely on forecasts and assumptions, and so will be subject to uncertainty. Information on suppliers’ realised costs is available in the financial statements published by the six large energy suppliers. See Understanding the profits of the large energy suppliers.
- The index does not include estimates of suppliers' ‘back-office’ operating costs (such as the costs of billing or metering – including the costs of the smart meter rollout) or their profit margins, which suppliers will seek to cover when setting their prices.
- The index is based on trends in the average prices of wholesale gas and electricity forward contracts in the month prior to the update. Suppliers will take different approaches to purchasing their wholesale energy, and many will buy their energy over an extended period. The index does not seek to estimate any impact this may have on a supplier’s costs.
- Other elements of costs are also likely to vary across individual suppliers. For example, suppliers may have some flexibility in how they meet their obligations under government programmes. This could mean, for example, that suppliers see different year-on-year changes in costs than indicated by the index where they have chosen to meet their obligations under the ECO scheme at the start of the delivery period (the forecasts used in the index are based on a flat delivery profile). Network charges will also vary between suppliers depending on things like the regional profile of their customer base.
- The index is calculated for a customer with typical consumption. We have held consumption fixed over time to increase comparability with trends in suppliers’ prices (which are also typically expressed for a given level of consumption). In practice, energy use will vary from one year to the next, depending on temperatures. Energy use is also subject to long-run trends, for example as a result of increasing energy efficiency. Trends in consumption will also have a significant impact on the size of customers’ bills.
- Capacity market payments were included in the index from winter 2017, we have categorised these as wholesale electricity costs. We consider that this allocation best reflects the nature of these costs. We intend to keep under review what further detail might be provided on the costs associated with different government programmes.
- Since the August 2017 update, we have included the additional costs associated with the expected exemption of Energy Intensive Industries from the costs of the Renewable Obligation scheme, following the Government’s announcement in December 2017. The Government’s decision on implementing the same exemption for the Feed-in Tariff scheme has yet to be published, and so the possible impact of a similar change to the way this programme is funded is not currently included.
Further details of how we calculate the index are provided in our methodology document.
We are always looking for ways to improve our data. If you have feedback, please contact us at firstname.lastname@example.org.
Below you can view publications and updates relating to our monitoring of suppliers' costs, and earlier monitoring under the Supply Market Indicator.