Electric boiler vs gas boiler: which is right for your home?

The short comparison

Both appliances heat water that runs through your radiators, and both come as combi, system and heat-only versions. The difference is the fuel, and that changes the installation, the running cost and what the property's supply has to carry.

Running costs: why gas usually works out cheaper

An electric boiler turns close to all of the electricity it uses into heat, and a modern condensing gas boiler is not far behind on the gas it burns. On efficiency alone the two look similar. What separates them is price. Under the Ofgem price cap, a kWh of electricity has cost several times as much as a kWh of gas, so the same amount of heat costs noticeably more from an electric boiler on a standard tariff.

How much that matters depends on how much heat the home needs. In a small, well-insulated flat with low heating demand, the difference over a year may be modest and can be outweighed by the saving on installation. In a draughty Victorian terrace or a family house with two bathrooms, the gap adds up quickly.

Off-peak electricity tariffs can narrow it. Some electric boilers are paired with a hot water cylinder or thermal store that heats overnight on cheaper rates. That only works if the system is designed around the tariff, so check the current Ofgem cap and the tariff you would actually be on before comparing figures from a brochure.

Installation: where electric boilers score

A gas boiler needs a gas supply of the right size, a flue that meets the positioning rules, a condensate pipe to a drain and a Gas Safe registered engineer to fit and commission it. In some London flats, especially in converted buildings and blocks with freeholder restrictions, one of those is the obstacle: there is no acceptable flue route, the gas pipe would have to cross communal areas, or the building does not allow new gas appliances at all.

An electric boiler avoids all of that. It can go on an internal wall, in a cupboard or anywhere with a suitable electrical supply and access to the heating pipework. There is no flue terminal on the outside wall and no condensate pipe to freeze in winter. If you are weighing up moving a boiler to a new position, an electric model can open up locations a gas boiler cannot use.

An electric boiler is a large fixed load. It needs its own dedicated circuit, and the work must meet the wiring regulations and be certified by a qualified electrician. Do not let anyone connect one to an existing socket circuit.

The electricity supply is the real limit

Most homes have a single-phase electricity supply, and the main fuse caps how much current the whole property can draw at once. A large electric boiler running alongside an electric shower, an oven and a kettle can push against that limit. That is why electric boilers tend to top out at lower outputs than gas boilers, and why larger properties sometimes need a supply upgrade from the distribution network operator before one can be fitted.

Before choosing electric, ask for the main fuse rating to be checked and a load assessment made. If the property has older wiring, an EICR will show whether the installation is in a fit state to take the extra load. The same question comes up when a hot water cylinder is replaced and the immersion wiring is found to be inadequate.

Hot water: combi, cylinder or thermal store

Electric combi boilers exist, but heating tap water instantly takes a lot of power, so their hot water flow rate is often lower than a gas combi's. For more than one bathroom, an electric system boiler with an unvented cylinder usually performs better, because the cylinder stores water ready for peak demand and can be heated off-peak.

A gas combi remains the most common choice for flats and smaller houses on gas, and a gas system boiler with a cylinder for larger ones. Our guide to the types of boilers explains how combi, system and regular boilers differ, whichever fuel they run on.

Carbon, grants and the future of gas

An electric boiler burns nothing in the home, and its carbon footprint falls as the electricity grid gets cleaner. It does not qualify for the Boiler Upgrade Scheme, which is aimed at heat pumps, and it uses more electricity for the same heat than a heat pump does.

There is currently no ban on fitting a new gas boiler in an existing home, as our gas boiler ban guide explains, so you do not need to abandon gas because of a deadline. If lower carbon matters to you and the property suits it, compare a heat pump as well as an electric boiler before deciding.

Which one should you choose?

Use the lists below as a starting point, then get the property looked at. The right answer depends on the heat demand, the supply you already have and how the home is used.

• Choose gas if you already have a suitable gas supply and flue route, the property is a house or a large flat, and you want the lowest running cost on a standard tariff
• Choose electric if there is no gas, gas is not permitted in the building, no flue route is acceptable, or the flat is small and well insulated with low demand
• Consider electric with a cylinder if you can use an off-peak tariff and have space for storage
• Look at a heat pump if you want lower carbon heating, have outdoor space and can size the radiators and cylinder to suit
• Replacing a working gas boiler with electric purely to avoid servicing rarely pays; compare the whole running cost first

Get advice before you replace your boiler

Loyal Plumbers covers London and inside the M25 with 10 vans, and our Gas Safe registered engineers carry out all gas work. If you are deciding between electric and gas, call 020 4652 8585 or send an enquiry with the size of the property, how many bathrooms you have, whether there is gas in the building and what you have now. We will look at the heating system and the practical constraints and tell you which route makes sense, before you commit to anything. Our guide to comparing boiler quotes explains what a proper quote should include.