Could heat batteries become eligible for the Boiler Upgrade Scheme?

The barrier is certification, not policy intent. Every heating system installed under the scheme must meet the relevant MCS standards approved and published by the Secretary of State, and installers must be MCS certified³. Heat batteries cannot yet be certified against a thermal energy storage standard, so they cannot satisfy that condition. MCS consulted on a Thermal Energy Storage System Standard in March 2025 and announced a pilot in September 2025⁵.

For a household, the practical position is that a heat battery can be bought and installed now, but not with scheme money. The technology itself is well established as a category: energy storage systems include battery storage, thermal storage and heat batteries, and heat batteries store energy as heat from electricity, including grid power or a home renewable source, or from surplus heat from a boiler, heat pump or another heating system⁶.

What the Boiler Upgrade Scheme funds today

The scheme provides grants to assist with installation costs, and its purpose is to cover part of the cost of replacing a fossil fuel heating system with a renewable heating system¹¹. It provides upfront capital grants to support the installation of heat pumps and biomass boilers in homes and non-domestic buildings¹³. The original fund was £450m, announced in October 2021, spent on grants that predominantly subsidise the upfront cost of replacement¹⁴.

Eligibility turns on replacement. A household must be fully replacing an existing fossil fuel system such as an oil or gas boiler, or an electric heating system such as storage or panel heaters, and there is no funding for replacing existing low carbon heat systems¹⁵. Fossil fuel heating systems include oil, gas, electric or LPG¹⁶. Hybrid systems, meaning any combination of a boiler and electric heat pump whether installed as a split or integrated system and whether on or off the gas grid, are not eligible, and neither is the replacement of low carbon heat systems¹⁷.

The scheme operates in England and Wales¹⁸. Applications properly made on or after 28 April 2026 fall under the current guidance, and uplifted grants for eligible off-gas grid properties apply to applications on or after 21 July 2026³. The scheme opened for grant applications on 23 May 2022¹⁹.

For energy independence, the scheme's design matters as much as its value. It pays to remove a fossil fuel appliance entirely, which cuts a household's exposure to oil or gas supply and price. It does not pay to keep a boiler as a backup, which is why hybrid arrangements sit outside it. A heat battery, which can take surplus heat from a boiler as well as from a heat pump, sits awkwardly against that rule until the standards work is finished.

Heat batteries: what they are and how they store heat

A heat battery stores energy as heat rather than as electricity. The energy can come from electricity, whether from the grid or a household's own renewable source, or from surplus heat from a boiler, a heat pump or another heating system⁶. That dual input is what separates the category from a conventional hot water cylinder, which stores water heated by a single source.

Some heat batteries can be used as a thermal store within a central heating system, typically alongside a heat pump⁶. That is the configuration most relevant to grant eligibility, because it ties the battery to a heat pump rather than to a retained boiler. A conventional electric boiler, by contrast, usually includes a large hot water tank to store the heat²⁰.

The distinction between thermal storage and electrical storage matters when reading scheme documents. Energy storage systems cover battery storage, thermal storage and heat batteries as separate examples⁶. Electrical battery storage appears on the VAT relief list for energy-saving materials; heat batteries do not¹⁰. A household comparing the two is comparing products that are treated differently in both tax and grant rules.

What a heat battery does for independence depends on its input. Charged from a home solar array or a cheap overnight tariff, it shifts the household's heating demand away from the moment of use and reduces reliance on gas delivered by a supplier. Charged from surplus heat off a gas boiler, it improves efficiency but leaves the gas dependence in place, and that is the configuration the scheme's replacement rule is designed to exclude.

Eligibility: why heat batteries are not yet covered

Two separate conditions block heat batteries. The first is the approved list. The scheme's notice of approved grant categories and values sets out what can be funded, and thermal storage is not among the categories⁷. The second is certification. All heating systems installed under the scheme must meet the relevant MCS standards approved and published by the Secretary of State, and installers must be MCS certified and meet the MCS standards³. MCS certification is required for installations to qualify for the funding⁸.

The same logic appears in the Warm Homes: Social Housing Fund. Heat batteries will not be eligible for that fund until they can be MCS certified, and once MCS certified, SAP-eligible heat batteries will be eligible⁵. That wording sets out the sequence plainly: certification first, eligibility second. The same sequence applies to the Boiler Upgrade Scheme, where government has said grant support for heat batteries will only become available once technical product standards have been established².

There are also exclusions that would catch some heat battery designs regardless of certification. Fossil fuel hybrids are not eligible⁹. Exhaust air-to-air heat pumps are not eligible for support under the scheme at this time⁹. Air-to-air heat pumps are only eligible for residential buildings²¹. A heat battery paired with a retained fossil fuel appliance would run into the first of these.

For a household, the eligibility question is therefore not simply whether the product works. It is whether the product can be certified, whether the installation removes the fossil fuel appliance entirely, and whether the property has already taken public money for a low carbon heating system. A heat battery installed alongside a working gas boiler would fail the replacement test even after the standard exists.

The £2,500 grant: when applications are expected to open

Government has stated that a £2,500 grant for heat batteries will also be available once the legislation and appropriate product standards are in place¹. Independent guidance repeats the figure, describing £2,500 off the cost of installing a heat battery to work with a central heating system for eligible households in England or Wales⁶. No date for opening applications has been published.

The scheme's grant values have moved before. The government increased its grant by 50% for new heat pumps, announced in November 2023²³. The higher grant rate applies only to new applications submitted from 21 July 2026²⁴. Households may be able to access a grant of up to £2,500 for air-to-air heat pumps²⁵. The approved grant categories notice lists £2,500 as a grant value⁷.

The published figures do not settle every case. The approved grant categories notice gives £2,500 as a grant value, while other scheme material gives £7,500 for heat pumps, and no ruling settles which figure applies to which technology⁷. A household reading grant figures should check the specific technology and application date rather than relying on a single headline number.

The scheme has also been expanded in scope. Grants were expanded to include air-to-air heat pumps and thermal batteries, announced in November 2025². A consultation on reforming consumer protection for home upgrade schemes refers to support for installation of heat pumps, biomass boilers and heat batteries in homes and non-domestic buildings²⁶. Expansion of the categories and payment for heat batteries are separate steps: the first has been announced, the second waits on standards.

The standards that must be in place first: MCS certification and SAP eligibility

The MCS Thermal Energy Storage System Standard is the certification route being built for this product category. MCS consulted on it in March 2025 and announced a pilot in September 2025⁵. Until it is published and products can be certified against it, heat batteries cannot meet the requirement that all heating systems installed under the scheme meet the relevant MCS standards approved and published by the Secretary of State³.

Certification operates at two levels. Products are certified, and installers are certified. MCS describes a route for certifying products²⁷. On the installer side, heat pump installations funded by the Boiler Upgrade Scheme need to be carried out by an MCS-certified installer²⁸. The scheme's own installer guidance states that installers must be MCS certified and meet the MCS standards⁴.

SAP eligibility is the second gate. The Warm Homes: Social Housing Fund wording is explicit that once MCS certified, SAP-eligible heat batteries will be eligible⁵. SAP is the assessment method used to score a home's energy performance, and a measure that cannot be modelled within it cannot be counted. A heat battery that is certified but not SAP-eligible would still fall outside.

For a household, this is the part of the timeline that cannot be compressed by choosing a different installer or a different product. The standard is a sector-level document. Until it exists, no heat battery installation can be certified for scheme purposes, and no grant can be claimed, whatever the announced £2,500 figure says.

What a heat battery grant would mean for householders

A grant would change the upfront arithmetic of a heat battery installation, but not the underlying dependence. The scheme exists to help with the upfront cost of low carbon heating technologies²⁹. It provides a grant to help cover the costs of installing low carbon heating technologies, such as heat pumps³⁰. The government offers grants to homeowners to install low carbon heating systems such as heat pumps³¹. A UK Government grant helps pay for a heat pump or biomass boiler in England and Wales³².

What a heat battery adds to independence is the ability to store heat rather than buy it at the moment of use. Charged from a home renewable source or from surplus heat, it decouples heating demand from the grid's peak. What remains is the input: a heat battery charged from a gas boiler leaves the household on gas, and one charged from electricity leaves it on a supplier and the grid. The battery shifts when energy is used, not where it comes from.

The scheme's replacement rule shapes which version of that a household can fund. Because eligibility requires fully replacing an existing fossil fuel system, and because fossil fuel hybrids are not eligible, a grant-funded heat battery would need to sit in a system with no retained fossil fuel appliance¹⁵. That is a stronger condition than the technology itself requires, and it is the condition that would determine what a grant-funded installation looks like.

Households weighing a heat battery now are therefore weighing a product that can be installed and used, against a grant that has been announced but not opened. The related questions of how a heat battery compares with a cylinder, and how the leading products differ, are covered in heat battery vs hot water cylinder and Sunamp vs Caldera heat batteries. The wider picture of how storage technologies fit a home's independence sits in Emerging Technology and Household Energy Independence, and the certification landscape in Standards and Certification for Emerging Energy Products.