UK homeowner eyes electric boiler after adding solar panels, gets blunt warning: 'You'll regret it'

A solar-and-battery installation led one U.K. homeowner to a natural follow-up: If the house will be making some of its own electricity, does it make sense to swap out the gas boiler too?

Commenters generally agreed that solar can help lower power bills, but they argued that using an electric boiler for heating and hot water is usually one of the most expensive ways to electrify a home.

Here's what to know

In a Reddit thread on r/ukplumbing, the poster said, "The thought of all the household energy needs being met by 'free' electricity is obviously appealing."

They were already planning to add solar panels and a battery, but noted that this would still leave gas use untouched and asked whether more panels and batteries could make an electric boiler a sensible next step.

The pushback centered on both cost and practicality, with one saying "you will regret it."

One commenter warned, "Typically heat is needed in the winter, PV electric production is about 20-30% in the winter, therefore, all that power for your boiler comes from your supplier at 3x the price of gas."

Another was even less charitable: "Electric 'boilers' are literally insane. There is no such thing as an electric combi 'boiler' that will give an acceptable DHW flow rate."

Instead, what's typically best if looking to power a water heater from electricity is a heat pump water heater, which is several times more efficient than an electric resistance boiler because it moves heat from the ambient air into the water, with most models boasting advanced technology to supplement with electric resistance heating only during off-peak grid pricing or when demand for hot water is higher. 

One example of a heat pump water heater is Cala, which does have all of those smart features, though it is not available at this time in the U.K. It's also increasingly common to see a whole-home heat pump system that handles home heating and cooling as well as hot water in one package, such as Mitsubishi's Ecodan system, which is newly available in both the United Kingdom and United States.

Another option is a tankless water heater using electricity, which is about 3-4 times less efficient than a heat pump water heater but at least provides a couple of advantages over an electric tank unit: less wasted power to keep water hot, and less space used overall. A tankless water heater saves about $50-$100 per year over an electric tank unit, and for anyone with surplus solar power, might be a sensible cost-saving option.

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In all cases, while gas has its advantages and even more so in areas where gas bills are cheap, gas does introduce fire, explosion, and carbon monoxide risks into a home, whereas the latter two are completely eliminated with an electric unit, and even general fire risk is lower (as long as a quality unit is installed by a licensed professional) since there is never an open flame. 

Still, electric resistance heating is not great. Panels can reduce how much electricity a home buys during the day, and batteries can move some of that energy into the evening, but that does not change the underlying economics of direct electric resistance heating.

Much of the advice to consider heat pumps instead came down to efficiency.

"Electric boilers are ~100% efficient, and heat pumps 300-400%," one commenter explained. "Sounds mental but heat pumps use the energy to move heat from outside instead of turning it all directly into heat."

In practice, that means a heat pump can deliver several units of heat from one unit of electricity, while a boiler only turns that electricity straight into heat.

Some replies also focused on tariffs rather than hardware. One suggested, "You can heat a hot water cylinder with an immersion heater, but it's likely to make more sense to export the power at 12p and buy it back overnight to heat the cylinder at 8p."

What can be done?

Across the thread, the most consistent recommendation for people trying to cut gas use and keep bills down was to consider heat pumps instead of electric boilers. Multiple commenters pointed to them as the better option, especially in homes that are well insulated or otherwise workable for retrofit.

For hot water, others mentioned more targeted electric options such as immersion-heated cylinders, electric showers, and on-demand electric hot-water taps. Those approaches may not fully replace a central gas boiler in every property, but commenters saw them as ways to reduce fuel use without taking on a huge winter electricity bill.

One commenter added that solar panels and batteries may offer a different kind of benefit than many homeowners expect: "Main thing panels and batteries provide is access to wider range of tariffs."

The thread's bottom line was short and clear: "If you want electric heat, get a heat pump." 

Where can I learn more?

For homeowners weighing solar, batteries, and a move away from gas, the real questions are usually about upfront costs, winter savings, and whether a heating upgrade will actually lower bills. Incentives, smart controls, and smaller efficiency fixes can shape that math just as much as the choice between a boiler and a heat pump.

• In the U.S., homeowners can still use federal solar incentives to cut installation costs.

• A smart thermostat upgrade can pay for itself by trimming bills and emissions.

• In winter, reversing a ceiling fan can effectively heat a home without touching the boiler.

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