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Electric combi boilers - the pros and cons

Given the recent rise in gas prices and the UK government’s stated aim of making all newly built homes ‘zero-carbon ready’ by 2025, the need to move away from using gas to heat and produce hot water for domestic properties has been brought into focus.

One of the technologies that is seen as an alternative to a gas combi boiler is the electric combi boiler. Here we go through our views of the positives and negatives of this technology. As with all mechanical and electrical technologies used in domestic buildings, the most appropriate one will depend on the type of property that it is to be installed in, and the way that the building is used.

The pros:

Use electricity to power not gas Greener - 47% of grid electricity produced via renewables and rising
No direct carbon emissions No emissions released during operation
Installation simple  No flue pipes needed, the boiler does not have to be situated on an outside wall, Can work with existing radiator system
Maintenance simple  There are fewer moving parts to go wrong, so maintenance is simpler and cheaper
No carbon monoxide risk No gas so no carbon monoxide!
No need to be connected to the gas grid Can be installed in rural areas where gas is not available
Smaller footprint  Boilers are more compact can be used in smaller properties
Solar integration Integrate solar PV to reduce bills, predominantly for the production of hot water in summer


The cons:

More expensive than gas (Pre gas supply issues) Prices for electricity are 13p/kWh and gas 2.8p/kWh. But, a high quality electric boiler will consume less energy than a gas boiler. When combined with Atamate control, and if installed in a well insulated property costs may be only marginally more than gas.
Lower power output - gas combi boilers up to 35kW, electric combi boilers up to 9kW May struggle to meet the heating and hot water demand in larger properties
Flow temperatures lower May need to increase size of radiators to provide the same comfort level or improve fabric to reduce heat load
Higher capital cost Electric boilers tend to be more expensive to purchase than gas boilers
Less efficient than direct electrical room heaters There will be losses incurred with an electric boiler as the heated water gets to the emitters in each room
Less choice on the market Fewer options to choose from for end clients
May need a water tank alongside to ensure hot water supply If there are multiple bathrooms, or the occupants require a lot of hot water a separate tank with immersion may be required to ensure supply
Affected by power cuts If there is a power cut, the boiler will not be able to provide heating or hot water
May require upgrade to electrical supply Connected load for electrical boilers may be too high for existing supply to property


 If you are thinking of installing an electric combi boiler to replace an existing gas boiler, here are a few things that should be considered first;

  • The process of rethinking the heating and hot water systems in your house needs to start by understanding the building, specifically the heat losses for your property and each room within it. Will the new boiler provide you with the heating and hot water that your occupants need? What changes will need to be made to ensure your comfort levels are maximised.
  • Electricity is 3x more expensive than gas, and although electric boilers consume around ½ the energy of a gas boiler a simple swap will mean higher bills in the short term. But, prices could (and should) even out in the longer term. 
  • If installing an electric combi, you will need to control ie automating the turning on and off emitters. This will need to be more than simple thermostat control to ensure that rooms are not heated when unoccupied to reduce energy use.
  • Electric boilers can be appropriate in small properties where heating and hot water demand is low. In larger properties, an additional hot water cylinder will be required, and even then the boiler may not have the power to provide both heating and hot water. Gas boilers range from 24-40kW whereas electric combi boilers tend to range from 9-15kW
  • Design in renewables - think about your requirements for heat and hot water and design an appropriate solution. This can include solar PV and batteries. If these are all designed as one system you are more likely to end up with a system that is the most efficient and effective.

Next steps:

As atBOS can control any mechanical and electrical system, we can be, and are, technology agnostic. As such we can take an unbiased view on what technology or systems are the most appropriate for each project. We offer a free consultancy session for people with domestic buildings looking for advice on how to approach the heating, ventilation and hot water provision in their new or existing property.

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