Case Study 4 – Are Electric Boilers A Good Or A Bad Choice For EPC Ratings

epc ratings electric boilers

Electric Boilers In A Domestic Property

In a domestic property, a gas boiler will always produce a better EPC rating than an electric boiler. This is because it can cost up to 3 times as much to heat a home with an electric boiler compared to a gas boiler.

Because the EPC rating is based on running cost, an electric boiler will always rate lower. If the property is also poorly insulated, it may struggle to meet the Minimum Energy Efficiency Standard of an E rating. If you are considering installing an electric boiler in a residential property, you would be wise to get an epc carried out before you install it so that the exact impact on the epc rating can be determined.

Electric Boilers In A Commercial Property

However, in a commercial property, the epc rating is based on carbon emissions and an electric boiler produces less CO2 emissions than it’s gas counterpart and therefore will rate higher. The running costs would still be high and if wanting to stay with electric, an air con system would be a cheaper option that still has low carbon emmissions.

Because of the high running costs of an electric boiler, you will never find it as a recomendation on either a domestic or a commercial epc.

Case Study Overview

We recently carried out 2 EPCs on 2 very similar flats for a landlord. The main difference was that one had a new electric boiler with an efficiency of 100%, the other had an old gas boiler with an efficiency of only 65%.

These were the rating of the flats

Flat 1 – Electric Boiler 100% efficiency

EPC rating E 52

electric boiler epc rating
electric boiler

Flat 2 – Gas boiler 65% efficiency

EPC rating D 62

gas boiler epc rating
old gas boiler

Comparing electric running costs to gas

In this case study each property has a demand of 6,900 kWh per year to provide heating and hot water to the flat.

So using the cost of the fuel from the fuel comparison table below, the running cost for each flat can be calculated.

Fuel type
Electricity Standard
Mains Gas
Cost per KWh (pence)

*Source: Nottingham Energy Partnership

Electric Boiler 100% efficiency
Gas Boiler 65% Efficiency
Fuel cost before boiler efficiency (pence per kwh)
Fuel cost after boiler efficiency (pence per kwh)
Annual demand for heating and hot water (k Wh)
Annual running costs (£)

This example shows that even with a low efficiency gas boiler of 65%, the running costs are still 59.35% cheaper than to heat a home with a 100% efficient electric boiler.

As the epc ratings are based on running costs, the gas boiler will still rate significantly higher.

The EPC will also give a breakdown of the property’s energy performance. This is shown below.

breakdown of property energy performance

We often get uphappy landlords and homeowners complaining that the epc must be incorrect as it rates their new boiler as being very poor.

In these cases we have to explain that the EPC is not saying there is anything wrong or poor about their boiler, but rather that it is poor compared to other heating sources that could provide heating and hot water to the property in a significantly cheaper way.



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Rickie Dickson

Written by Rickie Dickson

Rickie Dickson is an experienced and qualified domestic and non domestic energy assessor. He helps homeowners and businesses in all matters relating to energy efficiency, from meeting building regulations compliance to improving a property’s energy rating score.