With home heating responsible for nearly a fifth of emissions in the UK alone, scaling up domestic TES is critical to achieving net zero. Johan du Plessis, CEO at tepeo argues that smart heat batteries are vital to accelerate the transition to low-carbon heat while keeping the grid in balance.
Electric storage heating technology, like night storage heaters, isn’t a new concept. Yet, despite having been around since the early 1960s, it is yet to become mainstream. According to the latest census, only nine per cent of households in England and Wales had electric-only heating.
A primary limitation of night storage heaters is that they aren’t installed with wet heating systems (radiators or underfloor heating), which is currently used in approximately 23 million UK homes. Switching to this type of storage heating would entail replacing all wet radiators with night storage heaters – which would have a huge carbon footprint, not to mention the cost and disruption for homeowners.
From storage heaters to heat batteries
Research and development have, more recently, focused on optimising storage materials and product design while integrating smart capabilities. The outcome of this effort has been the modern heat battery boiler.
Heat batteries and night storage heaters are based on similar principles. The main difference is that heat batteries are specifically designed to integrate into existing wet heating systems. With this technology, households can eliminate their gas boilers — and the associated greenhouse gas emissions — without replacing radiators. As mains gas is the only heating source for over two thirds of UK households, switching to heat batteries can be transformational.
However, not all heat batteries are created equal. While some are predominantly aimed at water heating, others are specifically designed for space heating.
Different materials, different applications
Some heat batteries use phase-change materials to store thermal energy. These materials have minimal heat loss, and are typically used in hot water production to replace traditional domestic water cylinders. Due to their lower energy density, they are typically unsuitable for space heating.
By contrast, magnetite materials display two-to-three times the energy density of phase-change materials. These heat batteries can reach temperatures as high as 800 degrees while being fully insulated and enclosed for complete user safety. Reducing size and footprint is essential to making TES suitable for homes where space comes at a premium.
How can heat batteries complement heat pumps?
Heat pumps have established themselves as the go-to low-carbon heating technology, thanks to government subsidies. Widespread adoption of these heating systems remains critical to achieving net zero. However, there are limitations to how many heat pumps can be installed.
Firstly, not all UK homes can be fitted with heat pumps. Around 20 per cent of the housing stock, including millions of traditional terraced houses, present challenges to heat pump installation, due to insufficient outdoor space, and this percentage may be even higher. A 2024 study from the University of Warwick found that, although around half of UK homes were “eligible” for heat pump installation subsidies, only eleven percent of homes were likely to be “heat pump-ready”. Costs to upgrade pipework and radiators, lengthy installations and planning permissions are other barriers to adoption.
Secondly, the International Energy Agency (IEA) warns that “without improving efficiency in parallel” heat pumps can nearly triple their peak demand during winter. Therefore, retrofitting combined with “careful grid planning and demand-side management”, will be critical to mitigating this surge in demand.
Highly flexible technologies like heat batteries can complement heat pumps in two ways. They can be deployed in houses unsuitable for heat pumps, making decarbonised heating accessible to all, and they can ease pressure on the grid by shifting energy demand away from peak times.
Being smart about heat storage
Similar to the batteries in smartphones and EVs, modern heat batteries use smart algorithms to optimise energy use. Demand prediction algorithms analyse historic patterns and weather forecasts to determine accurate heat requirements. In addition, charging algorithms optimise energy use based on the household’s electricity tariff and grid carbon intensity, ensuring that the battery only recharges during off-peak times when electricity is the cheapest and the cleanest. These algorithms can even adapt to the most advanced dynamic tariffs, reflecting half-hourly wholesale electricity costs.
Heat batteries can help balance the grid by completely decoupling energy consumption from heat demand – recharging only when demand is at its lowest, and releasing heat only when this is actually needed. In addition, they constantly monitor grid frequency and can stop charging in response to frequency drops.
Faster installation, faster decarbonisation
Many UK households only decide to replace their boiler when it breaks down, meaning speed of installation is a critical factor when selecting a new boiler. Heat batteries can be installed in 1-2 days, minimising the time that a family spends without heating or hot water.
Installers can learn to fit a heat battery in less than a day. They don’t need the gas safety or refrigerant training that would be required for gas boilers or heat pumps, respectively. Speed and ease of installation are key to accelerating the uptake of low-carbon heat technologies.
The future of heat batteries
As dynamic energy tariffs evolve, heat batteries will be able to meet the higher heat demand of larger houses without increasing their carbon footprint – and, potentially, even reducing it. This evolution will involve charging flexibly throughout the day, rather than in the single overnight period typically seen in existing smart tariffs.
Another fundamental advancement will be integrating space and water heating into one product – similar to how combi boilers work. While space-heating batteries already enable indirect water heating via a water cylinder, these devices will, in future, be accessible to homes without water cylinders.
By continuing to optimise product design and smart capabilities, heat batteries will be critical to the UK’s transition to net zero. This technology can bring low-carbon heating to homes while helping ease pressure on the grid.
Installer insight – case study
Heating engineer Martyn Jones is the director of Bewdly-based M4RT, a company committed to choosing the right product and delivering tailored heating solutions to keep customers warm and reduce both their energy bills and carbon foot print. Martyn shares his firsthand experience of installing heat batteries.
I was hesitant at first, as most boiler professionals who are used to working with gas are but once I put tepeo’s ZEB® in and it worked the same as a boiler is supposed to I couldn’t believe it – it was amazing.
I thought to myself, for somebody who can’t have an air source heat pump or doesn’t want the upheaval associated with one, this is a perfect option. It is exactly like a gas boiler, it heats the radiators the same, pipework you can pretty much keep the same and so I thought…perfect. It’s another choice for our customers.
The training for the installation process is very straightforward. If you’ve been working in the trade and involved with heating for a while and already know your stuff, this is second-knowledge. It roughly takes a good day and a half to install the ZEB, which is a standard install of a new boiler, so the process is the same. We have to ensure the system is clean as obviously if you’re removing an old boiler you need to brick up the hole and then plaster and make good then remove all the old pipework.
Good for customers. Good for us
The tepeoPRO App is brilliant, I wish more gas boiler manufacturers had a similar App which tells you exactly what the boiler is doing and exactly what you need to know as a heating engineer. I love the App, I think it is great.
The best thing is that the ZEB is delivered onsite by the tepeo team – they bring it in and position it exactly where it needs to be and if not we can always move it to where we want it using the jacking wheels. The best thing about it is, it has been well thought about and the process is very straightforward.
Our customers say that the ZEB is very little hassle – our Trustpilot reviews for ZEB installs are incredible.
Image credit: tepeo
