Storage Heaters: How They Work

A storage heater is an electric heater that charges up on cheaper, off-peak night-time electricity and stores that heat for use the next day, which is why they are sometimes called Economy 7 heaters¹. Inside, electricity heats ceramic or clay bricks overnight, and the heater then releases that heat gradually through the day². Unlike a plug-in electric heater, a storage heater does not produce heat instantly: it relies entirely on the heat stored overnight, so planning ahead is essential³.

The economics rest on the gap between night and day electricity prices. Night-time electricity on Economy 7 is much cheaper, typically about half the price of the day rate, though the day rate is more expensive than a standard single-rate tariff². Get the controls right and night storage heating is a cheap form of electric heating; leave the settings alone and the same heater wastes money⁴. Modern high heat retention models, which must retain at least 45% of their heat under the standard used in UK energy assessments, hold heat for longer and can be up to 27% cheaper to run than standard storage heaters².

How storage heaters store and release warmth

A storage heater is a heavy, wall-mounted electric appliance whose job is to shift heating from the hours when electricity is expensive to the hours when it is cheap. It works by storing heat generated from cheaper night-time electricity and releasing it during the day². The heat is stored inside the heater's core, which is often made from heavy clay blocks⁹, or from ceramic or clay bricks⁶. Because the bricks are dense and the case is insulated, the heat leaks out slowly rather than all at once.

This is the fundamental difference from every other electric heater in the house. A plug-in electric radiator converts electricity to heat the moment you switch it on, at whatever the rate is at that moment. A storage heater buys its heat in advance, at night, and spends it through the day¹⁰. The trade is fixed in time: the heater cannot decide at six in the evening that it would like more heat at the night rate. It relies on the heat stored overnight, so planning ahead is essential³.

Older storage heaters manage this with two manual dials. The input or charge control regulates how much heat is stored up during the night: set higher in cold weather, turned down or off in warmer weather⁷. The output control governs how quickly the stored heat escapes into the room. More modern storage heaters use digital controls instead, while older heaters have manual controls³. Modern models generally come with improved heating controls, including an automatic charge control, a thermostat and a programmer⁹, and a thermostat lets you set the temperature you want the heater to warm the room to³.

Why overnight charging relies on off-peak power

Storage heaters charge during off-peak hours when electricity is cheaper, usually overnight³. The charging and the releasing are two separate phases: a charging phase, when the elements heat the core, and a heating phase, when the stored warmth is given out into the room³. The two are linked by a delay of up to a day, which is the practical heart of living with storage heaters.

The input setting is the household's main lever on cost. Automatic charge control regulates how much energy you use by storing more or less heat at night³. On older manual heaters the input dial has to be moved by hand to match the weather; on digital models, sensors and smart controls store just the right amount of heat³. Once they are set, digital controls are easier to run than manual ones because they automatically store enough heat for your set routine³.

Two safety nets matter. First, most older storage heaters will only charge up at night, so the input setting can be left without danger of using expensive day-rate electricity². Second, some heaters include a boost function for when the stored heat runs out, but this uses more expensive on-peak electricity⁸. The boost setting on an older night storage heater uses expensive daytime electricity, not cheap-rate stored heat, and should only be used if the stored heat has run out². Some specific storage heater models that use particular time of use tariffs may need to be left on all the time³.

The off-peak tariffs built for storage heaters: Economy 7 and Economy 10

Storage heaters were built around off-peak tariffs, and the two main ones are Economy 7 and Economy 10. Storage heaters use these tariffs for cheaper energy at night⁷, storing heat generated from the cheaper nighttime rates they provide⁶.

Economy 7 gives a cheaper rate for seven hours, usually between midnight and 7am⁷, though the exact window varies: the cheaper period runs for a seven-hour period at some point between 11.00pm and 8.00am, and your regional network operator defines the hours, which can be between 7 and 9 hours depending on the region¹¹. The meter tracks usage on two separate rates: a 17-hour day (peak) period and the cheaper night period¹¹. For energy customers who have electric storage heaters, the Economy 7 tariff is an ideal option, as they can be heated overnight and used to give off heat the following day¹². As a general rule of thumb, you would need to use more than 35% of your electricity at night to make Economy 7 cost-effective¹¹. Economy 7 remains on offer as a tariff from most energy suppliers¹¹.

Economy 10 provides 10 set hours of cheaper off-peak electricity: three hours in the afternoon, two hours in the evening and five hours through the night⁷. Three of these hours are in the afternoon and seven are overnight¹¹. The afternoon and evening windows suit households that want heat at times a storage heater cannot easily deliver, but Economy 10 tariffs typically only offer five hours of heat at night¹³. While Economy 10 offers unit rates of up to half the price of peak rates, the standing charges are often higher¹³. To get an Economy 10 tariff you must have an Economy 10 meter, and your property should be based on an electric rather than gas heating system⁷. Because of the complexity of the three different rates, many price comparison sites cannot support comparisons for Economy 10 meters¹¹, and a supplier may charge a fee to install the meter, as they are fairly uncommon¹³.

In Scotland, the picture is broader: Total Heat with Total Control, Economy 7 and Comfort Plus are meters and tariffs designed to work with storage heating¹⁴. UK energy assessments recognise electric storage heaters on 7, 10 or 24 hour supplies⁵.

How to spot the right meter

Economy 7 requires a special multi-rate meter to be installed at your home¹⁵. Without one, the household is on a single rate and the whole off-peak saving is unavailable.

The meter itself is easy to check. An Economy 7 meter has two sets of numbers, one marked low, which means night, and one marked normal, which refers to the day¹². These two sets of numbers are typically marked low and normal, or the meter shows one set marked Day Rate with a button to switch to the off-peak reading¹. If your bill shows two different electricity rates, one for night and one for day, that is the other confirmation.

If you have an Economy 7 meter and tariff, you typically get charged at a cheaper rate for energy used during the night¹⁵. That cheaper rate applies to everything used overnight, not only the heaters, which is why households on Economy 7 are often advised to run washing machines and dishwashers overnight too. If you are on Economy 7, you might also need to keep your immersion heater on overnight to get hot water at the night rate¹⁶.

Low charging costs but higher unit prices

The running cost story has two halves that pull in opposite directions.

The first half is favourable. Storage heaters use electricity at a cheaper rate to store heat for later use¹⁷. In homes without access to the gas mains, storage heaters are cheaper to operate than a standard electric heater⁶, and electric heaters that heat directly, on the day rate, tend to be more expensive to operate in comparison⁶. Night storage heaters are a cheap form of electric heating if you understand the controls, regularly update the settings to match the amount of heat you need, and are on the Economy 7 tariff⁴. Plug-in electric heaters, by contrast, do not effectively heat a home and are very expensive to run¹⁶.

The second half is the price of electricity itself. Electricity is around four times more expensive than gas per unit¹⁰, so even off-peak electric heating costs more per unit of heat than a gas boiler does. Official figures bear this out: for a three-bed semi-detached house, electric storage heaters cost £3,000 to £3,800 a year, the most expensive fuel type assessed, in figures covering Great Britain as of March 2026¹⁸. A typical running cost of £912 a year is quoted for a flat, depending on the type of heater⁸.

Figures for a flat, by heater type⁸.

Two warnings sit inside these numbers. Dynamic storage heaters do not work with Economy 7, so their running costs are higher than night storage heaters⁸. And the boost function uses expensive on-peak electricity⁸, so a household that leans on boost all winter loses much of the off-peak saving. High heat retention models are more expensive to buy but lower to run than traditional or integrated models, making them the most cost-effective option over time⁸.

High heat retention units: improved insulation and controls

High heat retention storage heaters are the modern end of the market, and the name has a technical definition. A high heat retention storage heater is one with heat retention not less than 45%, measured according to BS EN 60531⁵. In practice, these models can retain up to 45% of their heat even 24 hours after they were last charged¹⁹. They are the most efficient type of night storage heater⁸.

What separates them from an old manual heater is a set of features that work together⁹:

• Better insulation: high heat retention models are well insulated and retain more heat than other storage heaters⁹.
• Automated controls: they have automated controls, and modern storage heaters have higher heat retention, meaning they hold heat for longer⁹.
• Weather-aware charging: these models estimate the next day's heating demand based on user heating habits and climatic conditions, so input settings need no adjustment².
• Faster heat release: modern storage heaters can release heat more quickly when needed, sometimes using a fan to send out warm air⁹.

The financial effect is measurable. Upgrading to a modern storage heater can help reduce energy bills by about 10%², and high heat retention models are up to 27% cheaper to run than standard storage heaters². Storage heaters made after 2018 must meet stricter efficiency standards and come with better controls⁹.

The market is moving in this direction. Under the Energy Company Obligation, 15,122 upgrades to a high heat retention electric storage heater had been installed under that measure as of August 2026²⁰, and high heat retention storage heaters appear as an eligible heating measure in local authority home improvement loan schemes such as Cornwall's²¹. For a household weighing a replacement, the choice is broadly between a cheaper traditional unit with manual controls and a dearer high heat retention unit that manages its own charging.

The drawbacks of storage heating

The limitations are inherent to the design, and no amount of spending on a bigger model removes them.

• The heat comes when it comes. Storage heaters can leave your home very warm in the morning and struggle to stay warm in the evening⁶. Because they need to charge the night before, any change to the input will not take effect until the next day¹⁴.
• No instant heat. Storage heaters do not produce heat instantly like a regular electric heater; they rely on the heat stored overnight³.
• Size and weight. Storage heaters are large and chunky, stick out from the wall and can be obtrusive, taking up a considerable amount of room⁶.
• One room per heater. You will usually need one per room¹⁹, because a storage heater heats only the space it stands in.
• Boost costs day-rate money. The boost function uses more expensive on-peak electricity⁸.
• Tariff lock-in. The savings depend on being on the right tariff, and dynamic storage heaters do not work with Economy 7 at all⁸.

Sizing rules exist to stop overspending on capacity. Official guidance says the heating appliance should not be sized for more than 120 per cent of the design heating load unless an explanation can be given²², a limit carried through consultation responses on the maximum oversizing of heating plant²³. The size of space heating systems should be designed using the heat loss calculation in BS EN 12831-1 for the dwelling, and systems should not be oversized²⁴.

What they cost to buy, fit and replace

Prices span a wide range depending on specification. Basic models cost as little as £150, but you can spend much more depending on what you are looking for⁶. Modern storage heaters can cost from around £400 each¹⁹. Installation is quoted per heater: traditional night storage heaters cost £200 to £400 per heater to install, high heat retention night storage heaters £400 to £800, and dynamic storage heaters £400 to £600⁸. A typical installation cost for electric storage heaters is £900 to £1,400 per room¹⁰.

Replacement is not a DIY job. A registered electrician should replace your storage heaters⁹. Storage heaters need a connection to the correct circuit in your home and are hard-wired to the circuit⁹, so the work involves fixed electrical installation, and the heater must land on the off-peak circuit to charge at the cheaper rate.

On the running side, the annual figures above apply: £912 a year for a flat with a traditional night storage heater on Economy 7, £676 for a high heat retention model on the same tariff⁸. Against the purchase price, the upgrade case rests on the bill saving of about 10% from moving to a modern storage heater² and the up to 27% lower running cost of high heat retention models against standard ones².

Looking after them: upkeep, safety and how long they last

Storage heaters are among the lowest-maintenance forms of heating. Electric space heaters need no regular maintenance²⁵, and electric heating generally needs very little maintenance, with safety checks only every five years¹⁰. This contrasts sharply with oil-fired heating appliances, which need annual servicing to stay in safe, working order²⁶. There is no flue, no combustion and no water: electric space heating does not normally require a flue or pipework²⁵.

The lifespan comparison favours electric heating too. Electric space heaters can last an average of 50% longer than a conventional fossil-fuel heat source²⁵. For a household, the practical implication is that a storage heater bought once is likely to outlast a boiler bought at the same time, with no annual service bill in between.

The regulatory position on controls is worth knowing. Official building guidance states that automatic control of input charge should be provided²⁷, and electric storage heaters are required to have automatic control of input charge and an adjustable heat release rate²⁸. Northern Ireland's decent homes standard treats electric storage heaters on an off-peak or Economy 7 tariff as efficient heating²⁹. In new build projects, an electric heater can be installed at the second fix wiring stage²⁵, and it is easy to add heaters to a system at any stage, as budgets allow, because they operate as stand-alone units²⁵.

Storage heaters across British homes

Storage heaters have a long history in the UK housing stock and a shifting place in it. They fell out of favour in the 80s and 90s as electricity prices increased and people wanted their heat on a more flexible schedule¹⁹.

The current numbers vary by nation. In Scotland, the Scottish House Condition Survey records storage heaters used by around 5% of the housing stock in 2024³⁰; a correction to the 2023 survey fixed the figures at 7% for storage heaters and 2% for other heating types¹⁸. Across England and Wales, a further 9% of households use electric heating¹⁵. These are not large shares compared with gas central heating, but they represent a substantial number of homes, concentrated in flats, rural areas and off-gas-grid properties.

The policy context is pulling in two directions. On one side, electric heating, both at the off-peak and standard rate, is now lower carbon intensive than fossil-fuel heating alternatives²⁵, and all electric resistance heating products are 100% efficient at point of use²⁵. On the other, the heat pump is the government's preferred replacement route: 90% of UK homes are assessed as having sufficient insulation and electrical capacity to operate a heat pump¹⁵. A parliamentary committee has also argued that the scope of heating grants should be wider to better support consumer needs, including key components such as hot water storage cylinders³¹. For storage heater households, the practical question is whether to upgrade within storage heating or move to a different technology altogether.

Storage heating and self reliance for households

Storage heating sits in an unusual position on the independence spectrum. On the plus side, it removes several dependencies at a stroke: no gas connection, no flue, no pipework, no annual service, no fuel deliveries²⁵. A storage heater household is not exposed to gas price shocks or heating oil supply problems, and because heaters operate as stand-alone units, the system can be expanded one room at a time as budgets allow²⁵. Charging overnight also shifts consumption to hours when the grid has more spare capacity, which is where the cheap rate comes from in the first place.

The dependencies that remain are different in kind. The household is tied to its electricity supplier and to the off-peak tariff: the whole economics depend on the supplier continuing to offer Economy 7, and on the meter registering the night rate correctly. The household is also tied to the meter's fixed clock, since the regional network operator defines the off-peak window¹¹. There is no storage of fuel in the sense an oil tank gives: the "fuel" is heat in clay bricks, bought the night before and spent within a day, so a power cut overnight leaves the home cold the following day in a way a wet system with stored hot water would not be.

The deeper question is where the technology sits in a decarbonising grid. Off-peak electric heating rewards using electricity when it is cheapest, which is the same logic that will govern heat pumps, smart tariffs and home batteries. High heat retention storage heaters, with their automated, weather-aware charging², are in effect an early form of smart heating. What they cannot do is convert the electricity to heat more efficiently than any other resistance heater: all electric resistance heating products are 100% efficient at point of use²⁵, so the saving comes entirely from when the electricity is bought, not how much is needed. A household that masters the controls holds most of the independence storage heating offers; one that does not pays day-rate prices for night-rate heat.