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The Top 3 Things That makes biggest difference to EPC rating?

Things that impact epc rating the most

Have you ever wondered how you can get the best possible EPC rating on your property?

There are many factors and back-end calculations that go into producing the EPC rating for a property. In this article we’ll look at the 3 main factors that contribute the most in deciding whether your property will have a good or a poor rating.

By understanding how these 3 elements work together you can understand where your efforts should be made to improve your ratings.

By improving the EPC rating, you will benefit from lower energy bills as well as having a more comfortable home living environment. Properties that have a higher rating are also more attractive to potential buyers or renters. Also these types of properties can also benefit from preferential mortgage rates from certain lenders.

As a qualified Domestic Energy Assessor, I’ll give you expect advice and explain why these 3 factors play such an important role in the rating of an EPC.

things that improve rating of epc

1. Fuel Source

The source of fuel used to heat the house has a massive impact on the epc rating. The lower the cost of the fuel, the lower will be home’s energy bills and the better will be the EPC rating.

Below is a cost comparison in kWh of typical fuels used to heat UK homes, from the cheapest to the most expensive.

Most Expensive
Least Expensive
Fuel source
Standard Rate Electricity
Bottled (LPG)
Off Peak Electricity
Wood Pellets
Bulk LPG
Natural Gas
Cost per kWh (pence)

Source: Nottingham Energy Partnership date October 2023

As can be seen from the table above, the cost of heating the home by electricity is nearly 4 times the cost compared to heating it by gas.

According to Ofgem, an average UK homes uses 11,500 kWh annually to heat the home. This means that to heat a home by peak rate electric would cost £3, 841 (11,500 x 0.334p) compared to gas of £993.60 (11,550 x 0.0864).

Because the main rating factor on the epc rating is the running cost, a gas heated property will rate better than all other fuel sources on a like for like basis.

By selecting an appropriate fuel source to heat the home, the heating system will cost less to run which will reflect in a better EPC rating.

2. Heating System and Controls

The heating system is the main engine used to heat the house. Therefore, an efficient heating system combined with a low-cost fuel source will result in a good rating on the Energy Performance Certificate.

Different heating appliances have different efficiencies. For example, all electric heaters are 100% efficient. That is, you put in 1 kw of energy and the appliance will produce 1 kw of heat energy. In comparison, the best gas boilers are only 89.9 %.

However, the efficiency itself is not the main factor alone. It is a combination of the heating appliance efficiency combined with the cost of the fuel that determines the rating. So for example, an electric heater that is 100% efficient but cost 33.4 pence per kWh to run will still cost significantly more than a gas boiler that only has an efficiency of 69% where the fuel cost is 8.64 pence per kWh.

This means a gas heating system will always rate better than an electric heating system.

Heating Controls
A heating system, regardless of type, should always have controls to control the temperature at which the heating comes on and off. In addition, it should have a means to control the time the heating comes on or off. This is normally by means of a programmer/timer.

Further efficiencies can be gained if different zones of the property can be controlled independently by means of either thermostatic radiator valves (TRV) or time and temperature zone controls.

The presence of appropriate heating controls will add 2 to 3 points to the EPC rating.

The final part of the equation is to ensure that the heating system has to work no harder than necessary to heat the home. This is achieved by having good insulation.

3. Insulation

A home with good levels of insulation will mean that the heating system takes less energy to heat the home. The benefits of good insulation are, the home will warm up quicker, stay warmer longer and cost less to heat.

This will also reduce the risk of mould and condensation that can form on cold surfaces.

The areas of the home that should have good insulation are roof, walls, and floors. 

Households can cut up to £175 off their heating bills every year by installing loft insulation and up to £135 by installing cavity wall insulation according to British Gas.

Many of the energy suppliers also offer grants on the ECO scheme.


What are good levels of Insulation?

You should aim to improve insulation to the following thicknesses as a minimum:

  • Loft – 270mm
  • Floors – 100mm
  • Cavity wall insulation – 50mm
  • Internal wall insulation – 50mm
  • External wall insulation – 90mm

What is a good energy rating for a house?

If your property has a cheap fuel source, an efficient heating system and good levels of insulation it will rate well and is likely to achieve an EPC rating of C or above.

An EPC rating of A, B or C is a good energy rating for a house. We ran our own calculations from data available on the governments energy performance of buildings open data source and found that 46% of properties in England and Wales have an EPC rating of C.

If it rates poorly on only one of the key 3 items, then it will likely fall in the average UK property band of a D rating.

If it rates poorly on 2 of the key items, then it will rate below average and fall around the EPC rating E band.

If it rates poorly on all 3 of the key items, then it will rate poorly and fall in the EPC rating band F or G. This means that it will not reach the Minimum Energy Efficiency Standard of an E rating which is the legal minimum standard required to be able to rent a property.

What are the minimum energy performance standards for 2023?

The minimum energy efficiency standard will remain at an EPC rating E. This standard applies only to rented properties.

Following an announcement by Rushi Sunak on 20th September 2023, the UK government scrapped the planned proposal to raise the minimum energy efficiency standard to a C for all rental properties in 2025.

Can you sell a property with an EPC rating of F?

You can sell a property with any EPC rating. The purchaser must legally be given a valid EPC which shows the current rating of the property.

Although there is no legal requirement for a property for sale to meet the minimum energy efficiency standard of an E, some mortgage lenders have their own lending criteria that may require a specific EPC rating before they will lend. Properties that rate F or G are not seen in a good light.

Can you get a mortgage on a house with a low EPC?

Yes you can get a mortgage with a low EPC rating. A low EPC rating can be defined as a property that is rated an F or G.

Many lenders will factor in stricter lending criteria if the EPC Certificate has a low rating, as it means the home will be more costly to run and will need additional financial expenditure to raise the rating. For example, HSBC will ask for a higher Loan to Value (LTV) if the EPC is a low rating.

If the property is for rental, then it will be extremely difficult to get a buy to let mortgage if the property is below an E. It is illegal to rent a property below an E rating, unless it has a valid exemption.

By understanding that 80% of the EPC rating is derived from the Fuel Source, The Heating System and Controls and the levels of Insulation, by addressing these 3 items will make it easier for households to substantially raise their EPC rating.


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