Electric boilers for wet existing systems

Come the year 2025, no more gas for new build homes. What are the alternatives, and what is economically possible?
My research has let me to the conclusion that electric boilers for a wet system (radiators) is possible but probably only for small two bedroom houses. For larger four bedroom houses a 25 30 KW system would be required . This would not be achievable with the average properties electric power supply (single phase)
A 3 phase supply would be expensive but demand for this connection will only grow as we approach 2025.
If somebody has the answer I would appreciate their thoughts

Peter Weston

Air source heat pumps.

Difficult on existing housing stock due to needing massively oversize radiators for lower flow temperature, and the need for super insulation to minimise the amount of heating needed. Easily doable on a new build though, with underfloor heating etc.

No gas in my parents’ village so when their coal fire central heating system broke the council replaced it with an electric boiler. This I think is 7kW and they already had a 4kW electric immersion heater for hot water. House is 1960s built 3 bed. Would work fine for me to heat the whole house but they like the living room hot so supplement it with a convector heater when required. They use about 15,000 kWh a year so getting on for £3,000 in round figures. Not too different to what they used to pay for coal hardly ever letting it go out.

Ground source heat pumps are the better option if you can install them. In the winter when you need the heat the most, the air has far less of it to give. The ground on the other hand is a pretty constant temperature all year round. Neither option is very good for existing wet radiator systems though.

Also better insulated and sealed buildings. With a well insulated property (either retrofit or new build), the energy requirements for your heating system (whatever it is) is drastically reduced. MVHR systems will likely become more common as keeping in heat also generally means keeping in moisture and stale air.

Absolutely. But I suspect that most retro-fits wont have any room, hence air-source will become the most popular systems despite their downsides.

I wholly expect air-source heat pumps (along with snake oil ceramic core electric heaters) to be the devices of choice being installed, but it’s still nonsense! As always, insulation sales people will sell you insulation, and heating sales people will sell you the largest boiler that they can get away with.

Personally I really don’t look forward to the UK starting to look like the US with heat exchangers haphazardly slapped onto the outside of buildings. Cabling is bad enough!

… not to mention the noise of all these things running overnight on off-peak electricity charging up heat batteries.

What’s a better solution for properties without enough land to install a ground source heat pump?

Bzzzzzzzzzzzzzzznnnnnnnnnnnnnnnnnnn thwooooooooooooooooooo

Yeah, not fun.

Better solution is honestly to work on sealing up draughts and insulating. If I thought there was any money in it, I’d be buying and hiring out a top of the range thermal camera to assist people with that goal.
I’m probably going to end up hiring one for work in a few weeks - looking forward to taking it home with me on an evening.

I could see vertical borehole ground source heat pumps becoming more common for houses with some but limited garden space. Other than that I can’t think of any better solution for >100% efficiency from electric heating.

It will be very interesting to see how the market develops as gas is phased out for domestic heating which it will have to be based on existing information. Currently ASHPs are roughly 4 to 5 times efficient over a calendar year (that is for every 5kw of heat coming out only 1kwh of electricity is needed going in). Look at the price of gas per Kwh and you will see why ASHP’s need that sort of efficiency! I think on a large housing estate it will be impractical for all houses to have an ASHP, they do generate a certain degree of noise so careful siting is needed and may not be possible on dense developments. As far as comparison between modern and old property my usage is just under 9000kwh/year for hot water and heating using an ASHP. But 15% year of my total electricity consumption is used for car charging so actual heating/hot water uses probably around 7700kwh. The house has a floor area of around 140 sq m and has underfloor on the ground floor only and radiators elsewhere. It is built to current building regs. If you do consider ASHPs have a look at those from Scandinavian countries where they have been around for many years - the overall design of the systems and software used to run them in my opinion is way ahead of most models installed in the UK. Ground source is clearly much more efficient and therefore much cheaper in terms of running costs if it is practical to do the external work needed.

Some very useful contributions to life after gas but we are entering a cliff edge in our fuel /energy requirements. In five years, if we believe what we are told,No gas to new build homes. Currently for 10 radiators we need 24 to 27kw and for 15 rads we need 28-34kW with gas. Only 3 phase 415 volts will give you this power in a fully electric wet radiator system. We do not have the infrastructure that is readily available to use this higher voltage.
Its now good Bulb preaching about their green energy credentials if the very green energy cannot be implemented, because our houses are not geared up for it. We worry about broadband but to heat our homes in the 21 st century should take priority.

Peter Weston

This would be true if the heat came from a basic purely resistive heating system that operates like a giant kettle. As @ddnyorks said above, systems like heat pumps are typically 4 to 5 times more efficient than resistive heating, since they are not converting the electric directly to heat but using the electric to move heat from outside to inside. Taking your upper value of a 34kW gas boiler, the equivalent heat pump would require something like 8.5kW which is easily doable on a standard domestic supply and less than your typical electric shower.

If ASHP can be made in the commercial volumes and the installation costs brought down this could gain some traction. With some solar input as well this could be one of the solutions for new build homes
There remain millions of homes with gas and oil central heating systems with radiators and when they come to replace their old boilers what do they do? They replace with the same as this will be the cheapest option, unless after 2025 gas/oil shoot up in price. They might of course look at electric boilers as the easiest and greenest option.
My conclusion is that unless there are some extremely good inducements made by government, we will be dependant on fossil fuel for many more years, and future generations will pay the cost.


I agree. De-gassing existing properties is practically impossible without extensive renovations.