Does a new London home’s EPC rating
tell you what your bills will be?
An Energy Performance Certificate (EPC) rates a home’s energy efficiency from A to G and gives an average household’s yearly energy cost. This guide explains what the rating and the cost are based on, why your bills can differ, and why it matters where the heat comes from in a new flat.
An EPC is a yardstick for comparison;
your use sets the bill.
An EPC rates a home from A (most efficient) to G (least efficient) and is valid for 10 years. GOV.UK says the better the rating, the lower the fuel bills are likely to be; but the rating uses standard occupancy assumptions and takes no account of how many people live in the home or how you heat it.
The yearly cost on the certificate is what an average household would spend on heating, hot water and lighting in that home, based on average prices in the year the certificate was made. It does not show today’s tariff, standing charges or your own use.
Some new flats get their heat from a heat network. Ofgem says the energy price cap does not protect you in that case; heat networks have been regulated by Ofgem since 27 January 2026.
What an EPC shows
According to GOV.UK, you need an EPC when you sell, rent out or build a home. The certificate contains information about the home’s energy use and typical energy costs, and steps to improve its energy efficiency and save money. The seller, landlord or letting agent must show you the EPC.
You can find a certificate on GOV.UK’s Find an energy certificate service and download it free. On it you will see:
- The current rating and the potential rating with recommended improvements.
- An average household’s yearly cost for heating, hot water and lighting.
- Recommended improvements and the home’s total floor area.
How the total floor area is measured, and why it can differ from the developer’s figure, is explained in our guide to flat sizes.
How the rating and the cost are worked out
New homes are assessed with the Standard Assessment Procedure (SAP), and existing homes with RdSAP, its reduced-data version. The current versions are SAP 10.3 and RdSAP 10.0.1. According to the certificate, a SAP assessment must be carried out on all new homes built after 1 April 2008 in England and Wales.
GOV.UK’s EPC guide says the rating uses “standard occupancy” assumptions, which may differ from how the building is actually used.
It takes no account of how many people live in the home, the appliances you own or how you choose to heat it. The guide says fuel bills are likely to be lower in a better-rated building; it gives no figure.
The cost on the certificate is tied to that year’s prices. A certificate made in 2021, for example, says its cost is based on average 2021 costs and that people living in the home may use different amounts of energy. The government also accepts that energy prices can change during a certificate’s validity and make cost information out of date.
What sets your bill
Ofgem says your bill can also vary with how your home is heated, for example if you use heating oil or your home is on a heat network.
The energy price cap is the maximum your supplier can charge for a unit of energy and the standing charge together; it does not limit your total bill. Ofgem sets the cap every 3 months.
What makes the bill differ between two flats with the same rating:
- How many people live there and how much you use the home
- How long, and at what temperature, you run the heating
- Your tariff: the unit rate and the daily standing charge
- Where the heat comes from: the flat’s own system or a heat network
Flats on a heat network
In some new buildings, heating and hot water come from a shared system for the building or the area, a heat network.
According to GOV.UK, since 27 January 2026 all heat networks in Great Britain are regulated by Ofgem and must register with the Energy Ombudsman’s redress scheme. Under the government’s plan, more complex regulation such as pricing and standards of performance follows from January 2027.
Ofgem states that you are not protected by the price cap if you get your heat from a heat network.
For a flat on a heat network, ask the seller in writing for the heat tariff, standing charge, metering and billing arrangements, and whether these costs sit in the service charge or on a separate bill. The service charge is explained in our leasehold guide.
EPCs when you buy off-plan
Under the 2012 regulations, the person carrying out the work on a new building gives the EPC to the owner no later than five days after the work is completed.
The same regulations do not require an EPC to be given to a buyer before construction is complete; once there is one, the seller must make it available free of charge at the earliest opportunity.
If you are buying off-plan, ask the developer for the home’s target rating and which heating system it was calculated with; any figure before handover is an estimate. GOV.UK’s guide, last updated in 2017, says most new buildings complying with the Building Regulations of the time achieve a C or B rating.
The EPC itself is changing. The government plans to replace the single cost metric with four headline metrics: energy cost, fabric performance, heating system and smart readiness. It has moved the launch of the reforms to the second half of 2027.
If you plan to let the home
You also need a valid EPC to let a home. Since 1 April 2020, landlords cannot let a home with an EPC rating below E unless they have a valid exemption.
The government has decided to raise the standard to the equivalent of EPC C; subject to Parliamentary approval, all tenancies will have to comply by 1 October 2030. Letting obligations are covered in our NRLS guide.
Five questions
to understand the bill.
A reminder only; your use and your tariff set the amount you pay.
Short questions,
short answers.
Is the yearly cost on the EPC what I will pay?
No. It is what an average household would spend on heating, hot water and lighting under standard assumptions, based on prices in the year the certificate was made. Your bill depends on your use, your tariff and standing charges.
What rating does a new home get?
GOV.UK’s guide, last updated in 2017, says most new buildings complying with the Building Regulations of the time achieve a C or B. Your home’s rating is on its own certificate; any rating given before handover is an estimate.
Does the price cap apply to a flat on a heat network?
No. Ofgem says you are not protected by the price cap if you get your heat from a heat network. Heat networks have been regulated by Ofgem since 27 January 2026 and must register with the Energy Ombudsman’s redress scheme.
An EPC lasts 10 years; can I use an older one?
The certificate is valid for 10 years, but its cost figure rests on prices in the year it was made, and the government accepts that price changes can make it out of date. Use the rating to compare homes, not the cost as a guide to today’s bill.
Is the EPC going to change?
The government plans to replace the single cost metric with four headline metrics (energy cost, fabric performance, heating system and smart readiness) and has moved the launch to the second half of 2027. Certificates made today still use the A to G rating.
We do not estimate bills;
this page is not advice.
This guide summarises, as general information, what GOV.UK, Ofgem and the relevant regulations publish; it does not state what any home’s bills or savings will be. Questions about a certificate can go to the energy assessor who produced it.
OGKinvest introduces buyers to new-home developers and is paid an introduction fee by the developer; when a developer pays us, we tell you.
The pages this
guide relies on.
- GOV.UK: Selling a home, Energy Performance Certificates. When you need one, A to G, 10 years, contents, the duty to show it.
- GOV.UK: A guide to energy performance certificates for the marketing, sale and let of dwellings (2017). Standard occupancy, household size and heating, bills “likely” lower, C or B for new buildings.
- GOV.UK: Find an energy certificate. Certificate wording: potential rating, average household cost, prices of the certificate’s year, SAP and 1 April 2008.
- Energy Performance of Buildings (England and Wales) Regulations 2012, regulations 5(2), 6(2) and 7A. No EPC required before completion, free of charge, five days.
- GOV.UK: Standard Assessment Procedure (8 June 2026). SAP 10.3 and RdSAP 10.0.1.
- GOV.UK: Reforms to the Energy Performance of Buildings regime (partial government response 21 January 2026, update 9 March 2026). Four headline metrics, cost information going out of date, second half of 2027.
- GOV.UK: Heat networks (11 February 2026) and the government response on heat network regulation (August 2025). 27 January 2026, Energy Ombudsman, January 2027.
- Ofgem: Energy price cap and standing charges explained and How your bill is calculated. What the cap limits, every 3 months, heat networks, heating type.
- GOV.UK: Minimum energy efficiency standard, landlord guidance (5 May 2026) and Improving the energy performance of privately rented homes: 2025 update (government response 21 January 2026). Rating E, EPC C and 1 October 2030.
Last checked: 16 October 2026. This page is general information, not a forecast of bills or savings. Energy prices and EPC rules change; check the current information on GOV.UK and Ofgem before you decide.
Let’s talk running costs
before you buy.
In a consultation we can go through the EPC, the heating arrangements and the service charge for the flat you are considering.
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