If you have an electric boiler, you’ll know that heating your home can be expensive. It’s a straightforward way to heat your radiators, but relying on electricity throughout the day can quickly add up, particularly in winter.
So, if you’re looking for ways to bring your heating bills down, a heat battery will offer a more cost-effective alternative, without changing the familiar way your home is heated. Heat batteries are cheaper to run and have lower associated carbon emissions than electric boilers – this is why the government is including heat batteries in the boiler upgrade scheme, but not electric boilers.
Let’s look at how the technology compares, what the potential savings could be, and whether upgrading makes financial sense for you.
Why are electric boilers expensive to run?
An electric boiler (also referred to as a “direct electric” or “electric flow boiler”) uses electricity to heat water for your radiators or underfloor heating, typically as and when your home needs warmth.
Other heating technologies, including heat pumps and heat battery boilers, also run on electricity, but they work differently.
The challenge with electric boilers is that they generate heat from electricity at the moment you need heating for your home or hot water.
For example, if your heating comes on at 6pm, your boiler will need to draw electricity at 6pm to produce that heat. If you currently have an electric boiler you’re likely on a flat (single-rate tariff) with a rate between 20p/kWh and 30p/kWh. This makes your heating very expensive. If you’re on a flexible (time-of-use) tariff it could be even more expensive as you’re likely to need your heating the most during peak times in the morning and evening.
Some electric boiler installations already use hot water storage to take advantage of off-peak tariffs, so costs will vary. But for systems that rely largely on electricity as heat is needed, there’s an opportunity to do things differently.
How is a heat battery different?
The tepeo ZEB heat battery boiler is also powered by electricity, but instead of using electricity when you need heat, it charges during off-peak hours and then stores that energy for when you need it.
It works in three simple steps:
- Charge: The ZEB uses electricity to heat its internal ceramic core, with Smart Charging helping it take advantage of cheaper, lower-carbon off-peak periods.
- Store: That heat is stored safely and efficiently, ready for when your home needs it.
- Heat: The stored heat is released through your wet central heating system, warming your home through radiators or underfloor heating.
The important difference is timing.
A heat battery boiler uses the same amount of electricity as an electric flow boiler to provide the same amount of heat. However, because it uses off-peak electricity which is typically around 65% cheaper than a single-rate price, it makes a real difference to running costs.
How much would you expect to save compared with an electric boiler?
For households currently using an electric flow boiler, the potential savings are significant.
Based on tepeo’s Cost and Carbon calculator, a home currently using 8,000 kWh of electricity annually for heating could potentially save approximately £918 a year by switching to a ZEB on a suitable heating tariff.
With an eligible EV-style tariff offering cheaper overnight electricity, your savings could increase to approximately £1,363 annually.
Here’s how the estimated running costs compare:
Electric boiler vs heat battery boiler annual running costs
Here’s how the estimated running costs compare for a home currently using 8,000 kWh of electricity annually for heating:
| Electric boiler | ZEB Heating tariff |
ZEB EV tariff |
|
|---|---|---|---|
| Annual consumption used for comparison | 8,000 kWh | 8,000 kWh | 8,000 kWh |
| Estimated annual electricity cost | £2,063 – £2,148 | £1,066 – £1,178 | £643 – £710 |
| Annual service and warranty | £80 – £120 | £153 – £179 | £153 – £179 |
| Total annual running cost | £2,143 – £2,268 | £1,219 – £1,357 | £796 – £889 |
| Potential annual saving | — | £918 | £1,363 |
Illustrative annual running costs based on 8,000 kWh of space heating demand. Actual costs and savings depend on your home, electricity tariff and charging patterns. Figures include estimated annual servicing and warranty costs.
Figures are illustrative estimates based on tepeo’s Cost and Carbon calculator, using 8,000 kWh of annual heating consumption. ZEB running costs are modelled using half-hourly charging optimisation, historical weather data (2022-2024) and typical household heating patterns. Actual costs and savings will vary depending on your property’s insulation, heating habits, electricity tariff and individual circumstances. Ranges are provided to reflect potential variations in running costs
Is a heat battery boiler worth the upfront investment?
A replacement direct electric boiler will usually cost less to install than a heat battery boiler, so if you’re comparing purchase prices alone, another electric boiler might seem like the obvious choice.
But when you’re investing in a heating system you’ll rely on for years, running costs deserve just as much consideration.
Let’s say your existing electric boiler is approaching the end of its life, and you’ve budgeted around £2,500 to replace it.
Rather than spending that money on another direct electric boiler, you could put it towards a ZEB heat battery boiler, with the potential to reduce your ongoing heating costs.
Here’s how the numbers could work:
| Cost breakdown | Amount |
|---|---|
| Illustrative ZEB + installation cost | £8,500 |
| tepeo Early Grant Match | -£2,500 |
| Cost after discount | £6,000 |
| Your existing boiler replacement budget | £2,500 |
| Additional investment required | £3,500 |
These figures are illustrative and based on assumed installation and replacement costs. Actual installation prices will vary. The tepeo Early Grant Match is subject to eligibility and availability. Any borrowing costs are excluded from the comparison.
In this example, upgrading to a ZEB would mean investing an additional £3,500 compared with replacing your existing direct electric boiler.
However, the reduction in annual running costs mean you would still have a payback vs an electric boiler of only 3-4 years. After this you’d be saving significant amounts every year.
Of course, the upfront investment is an important consideration. Some homeowners may choose to use their savings, while others might explore borrowing through their bank or an independent lender to help spread the cost.
If you’re considering a personal loan, it’s worth comparing interest rates, monthly repayments and the total amount repayable to understand how borrowing could affect the overall cost of upgrading. Any borrowing would need to be arranged independently, rather than through tepeo.
Remember, electricity savings aren’t guaranteed to cover loan repayments, so it’s important to make sure any borrowing is affordable regardless of how much you save on your heating bills.
Ultimately, it’s worth considering both the upfront investment and the potential long-term running costs when deciding which heating system offers the best value for your home.
Is a heat battery boiler right for your home?
If you currently have a direct electric boiler, particularly one that’s approaching the end of its life, switching to a heat battery could be worth considering.
A ZEB could be a good option if:
- You’re looking to reduce your electricity bills by making better use of cheaper off-peak electricity.
- You want to keep your existing radiators or underfloor heating, without completely changing how your home is heated.
- You’re planning to replace your electric boiler and want to consider the longer-term running costs rather than just the upfront price.
- You’re looking for a low-carbon heating alternative that doesn’t require an outdoor unit or large amounts of disruption..
Of course, a heat battery won’t be suitable for every home. Factors such as your heating requirements, available installation space, hot water arrangements and electricity tariff all play a part in determining whether it’s the right choice.
Find out how much you could save with a ZEB
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