Easy Fuel Comparison
How it works
The tool takes one figure for the heat a home needs each year, for heating and hot water, and works out what it costs to provide that heat with a gas boiler, an oil boiler, a heat pump and direct electric heating.
Drag the handle at the top of a bar up or down to see the fuel price, or the efficiency, needed for that running cost. A bar snaps level with another fuel when they match. Switching between Price and Efficiency puts the bars back to the entered figures. Tap a bar to see how it is worked out.
Figures are saved as you type, so they are still there when you come back from this guide or another page. Clear, at the top of the tool, removes them.
Property energy use
From an EPC
An Energy Performance Certificate (EPC) rates a home's energy efficiency from A to G and estimates the energy it needs each year. A home needs one when it is built, sold or let, and it lasts 10 years.
Find an EPC on GOV.UK. Search by postcode; it is free. This covers England, Wales and Northern Ireland. Scotland has its own EPC register.
On the certificate, look under "Heating this property". It says "Estimated energy needed in this property is:" followed by the kWh per year for heating and the kWh per year for hot water. Enter those two figures in the tool.
EPC figures are modelled on a standard household and heating pattern, so real use can differ.
No EPC: space heating
The design heat loss is turned into a yearly figure using the degree-days for the postcode area:
This is the MCS 031 a) 2.1(e) relationship worked in reverse, as MCS 031 a) Appendix A allows. Degree-days come from MCS 031 a) Appendix B, Table 1. Use the indoor and outdoor design temperatures the heat loss was calculated at.
Example: 6.2 kW at 21 °C indoor and −2.6 °C outdoor, Colchester (CO, 2,254 degree-days): 6,200 ÷ 23.6 × 24 × 2,254 ÷ 1000 = approx. 14,212 kWh.
Engineering judgement: homes are rarely held at the design indoor temperature throughout, so this figure may read high.
No EPC: hot water
Daily use is 40 litres per bedroom and bathroom, or 40 litres per occupant if that is higher (CIBSE DHDG 2026, Table 4-3), delivered at 42 °C from 10 °C cold mains.
Example: 3 bedrooms and 1 bathroom = 160 litres a day = approx. 2,173 kWh a year.
The cylinder storage temperature does not change this figure: a hotter cylinder sends less stored water, mixed with more cold, to give the same water at the tap. Storage temperature does affect heat pump efficiency, standing losses and pasteurisation, which are covered by the efficiency figure you enter or not included.
Running cost and standing charges
Running cost = fuel used × unit price + standing charges
Heating oil is converted from pence per litre to pence per kWh at 10.28 kWh per litre. This is the gross energy content of burning oil (DUKES 2025: 46.20 GJ per tonne ÷ 1,249 litres per tonne). Gross values match the way boiler efficiencies are rated and the way gas is billed.
Checking the prices
Electricity and gas start at the Ofgem price cap for 1 October to 31 December 2026, GB average, Direct Debit. Ofgem changes the cap every three months, from 1 January, 1 April, 1 July and 1 October. Check the current price cap on Ofgem and use the GB average Direct Debit figures: the unit rate in pence per kWh and the daily standing charge in pence per day. The same page gives figures for each region.
Gas includes 5% VAT; there is no VAT on electricity from 1 October 2026 to 31 March 2027. One quarter's prices are applied to the whole year.
Heating oil changes daily, so the tool starts it blank. Check today's heating oil price and enter the price per litre. If the price is shown without VAT, add 5%.
Standing charges. Every home pays the electricity standing charge, so it is added to every option. The gas standing charge is added to the gas boiler only. For the heat pump, oil boiler and direct electric options, the tool assumes the home has no gas supply. If the home keeps gas, for example for cooking, it still pays the gas standing charge (approx. £108 a year at the current price cap), so add that to those options.
Efficiencies
One figure per option covers both heating and hot water. The starting figures can be changed.
| Option | Starting figure | Source |
|---|---|---|
| Gas boiler | 92% | AD L 2021 (2023 amendments), Tables 6.1 and 6.2 |
| Oil boiler | 91% | AD L 2021 (2023 amendments), Table 6.3 |
| Heat pump | SCOP 3.5 | Mean published SCOP at 55 °C flow of 12 R290 models |
| Direct electric | 100% | All the electricity becomes heat |
Boilers in practice
The boiler figures are the minimum seasonal (ErP) efficiencies allowed by Building Regulations. Installed boilers rarely reach their rated figure. In an Energy Saving Trust field trial (43 gas boilers with a full year of data), regular boilers averaged 85.3% measured at the boiler (approx. 80.3% once cylinder and pipe losses were allowed for) and combi boilers 82.5%.
Heat pumps
SCOP 3.5 is the mean published seasonal figure at 55 °C flow (BS EN 14825, average climate) for 12 R290 models: Grant Aerona 290, Mitsubishi Electric Ecodan R290 and Samsung EHS Mono R290. A well-designed system running at a lower flow temperature will usually achieve a higher SCOP.
Smart tariffs
Heat pump tariffs charge different rates at different times of day. Over a year, what matters is the average rate the heat pump actually pays:
Example figures only: 60% of use at 15p and 40% at 26.32p gives an average of approx. 19.53p per kWh.
The shares are your assumption. They depend on how the system is run, for example heating the cylinder and warming the house during the cheaper periods. The electricity standing charge stays as entered.
Carbon
Factors are from SAP 10.3, Table 12, in kg CO₂e per kWh: gas 0.214, heating oil 0.298, electricity 0.086. They include methane and nitrous oxide as CO₂ equivalent.
Gas and oil factors hardly change, because they depend on the fuel itself. The electricity factor depends on how the grid generates power, so it falls as more comes from wind and solar. SAP 10.3 uses a projected figure for a cleaner grid. For comparison, the GB grid averaged 128.8 g per kWh in 2025 (approx. 0.129 kg per kWh), and existing-home EPCs (RdSAP 10) still use the older SAP 10.2 figure of 0.136.
What is not included
- Electricity for boiler and heat pump fans, pumps and controls
- Servicing, maintenance, installation costs and grants
- Cylinder and pipe heat losses on the No EPC route
- Secondary heating, such as a fire or plug-in heater
- Price changes through the year
Sources
- Ofgem energy price cap, 1 October to 31 December 2026 (Ofgem)
- Heating oil prices (oilcompare)
- DESNZ, Digest of UK Energy Statistics (DUKES) 2025, Tables A.1 and A.3
- Approved Document L Volume 1, 2021 edition incorporating 2023 amendments, Tables 6.1 to 6.3
- Manufacturer datasheets: Grant Aerona 290, Mitsubishi Electric Ecodan R290, Samsung EHS Mono R290 (SCOP at 55 °C, BS EN 14825)
- Energy Saving Trust, In-situ monitoring of efficiencies of condensing boilers and use of secondary heating (GASTEC at CRE, June 2009)
- MCS 031 a) Issue 2.0, 2.1(e), Appendix A and Appendix B Table 1
- CIBSE Domestic Heating Design Guide 2026, Table 4-3
- SAP 10.3 (June 2026), Table 12; RdSAP 10, Table 32
- GOV.UK, Find an energy certificate
- MoneySavingExpert, gas standing charges to be scrapped (October 2026)
- Energy Dashboard, 2025 Electricity Review
Support & feedback
If a calculation looks wrong, the tool misbehaves, or you have an idea to improve it, please get in touch. Use the link below, or the Support & feedback link at the bottom of the tool. Your build version is added to the email automatically.
About & Terms
Easy Fuel Comparison is part of Easy Heating Engineer, a set of tools for heating engineers and trainees.
Data privacy
This tool runs entirely on your device. Everything you enter stays in this device's browser storage and is not sent to any server or third party. There is no account, no tracking and no analytics. The heating oil price is kept for the day it is entered only.
Disclaimer and competence
This tool compares the yearly running costs and carbon of heating fuels, as an aid to training and discussion. It is a comparison aid only. It is not a quotation, a bill forecast or a system design, it does not replace a heat loss calculation or system design, and it does not by itself satisfy any MCS, Building Regulations or other regulatory requirement.
Results depend on the information entered and on the published data cited. Prices change, so check them before relying on any result. The user is responsible for checking all inputs and outputs, and for working within their demonstrated scope of competence. To the fullest extent permitted by law, the author accepts no liability for any error, omission, or any direct or indirect loss or damage arising from use of this tool or reliance on its output.
Copyright
© 2026 Easy Heating Engineer. All rights reserved. This tool may not be reproduced, redistributed, or modified without written permission. Sources (Ofgem, DESNZ, MCS, CIBSE, SAP, the Energy Saving Trust and manufacturer data) are cited for reference only.
Backups. Your figures are stored only on this device. Clearing the browser's site data, uninstalling the app, or losing or resetting the device will delete them. Clear, at the top of the tool, removes them yourself.