Are Storage Heaters Expensive to Run?

01

How storage heaters and Economy 7 work

A storage heater takes electricity during its charging period and keeps heat in its internal store for later release. The useful distinction is between buying energy and releasing it. Opening an output control does not start another free source of heat; it changes how quickly the stored energy reaches the room. A separate boost function may buy additional electricity when you use it.

Economy 7 divides electricity into day and night registers. The lower overnight price can suit a charging load, but the higher day price also applies to other daytime electricity. Compare the whole home over the same period. Cheap heating hours do not automatically compensate for an expensive daytime bill.

02

Work out charging energy before pricing it

Our calculator example starts with an explicitly entered 3.4 kW charging input and seven hours at that input. Multiplying them gives 23.8 kWh for a charging day. Repeating that assumed charge on 120 days gives 2,856 kWh. These are calculation inputs and outputs, not a recommendation to charge every heater fully on every winter night.

An automatic charge controller may draw less than the maximum input throughout the available window. A meter reading for the heater circuit, or a documented average input under the same settings, is a better basis than assuming the nameplate rating runs continuously. Do not use the heater's heat output in place of its electrical charging input.

03

Cost per day and month using your tariff

Multiply charging kWh by your actual night price in pounds per kWh. For a month, add the energy of the charging days in that month rather than assuming the same demand throughout the year. Daytime boost energy needs its own day price. If the boost and the overnight charge are already included in meter totals, avoid adding them twice.

The Ofgem multi-register comparison figure is not a pair of Economy 7 prices, so our worked example uses illustrative prices: 15p/kWh at night and 30p/kWh by day. These are example prices, not a quote or an available offer. Use the prices on your own bill in the calculator. At 15p, the 23.8 kWh charge costs £3.57 a day. A month with 30 charging days uses 714 kWh and costs £107.10. The 120-day season uses 2,856 kWh and costs £428.40.

For comparison, the same 23.8 kWh costs £7.14 at the 30p example day price. On a single-rate tariff at the October to December 2026 GB Direct Debit cap reference of 26.32p/kWh, it costs £6.26. This compares the heater load only. Other day and night use and both standing charges decide which plan costs less for the whole home, so a low night price on its own cannot prove a saving.

04

Should you leave the heater on all the time?

Separate keeping the charging supply available from leaving a daytime boost operating. They are different decisions. Turning off the supply can prevent the next charge, while closing a manual output control mainly slows the release of energy already stored. The best arrangement depends on the controls fitted and when the room is occupied.

Before changing a schedule, check the model's instructions and ask the supplier which meter hours apply. Record whether the room remains comfortable late in the day and whether boost is regularly needed. That gives a more useful starting point than a blanket rule to leave every heater on or turn every heater off.

05

Input and output settings

On traditional controls, input sets the next charge and output governs release. Energy Saving Trust explains why an input change may not affect the heat already stored. Follow the manufacturer's guide when adjusting automatic, weather-responsive or programmable controls; the labels on a newer heater may not match an older manual model.

Change one setting at a time and compare similar conditions where possible. Note the charging meter reading, occupancy and any boost use. If the heater releases most of its warmth before the room is needed, investigate controls and timing before assuming that a larger nightly charge will solve the problem. Persistent faults or an unsuitable installation need an installer.

06

When a different heater could cost less

A portable heater used for a short, occupied period may buy less total electricity than a large storage charge that mostly heats an empty room. Conversely, its electricity may be charged at the more expensive day price. Compare required service, measured energy and applicable prices, rather than treating all heat or all hours as interchangeable.

Include the practical cost of changing equipment and any supply alterations separately. A running-cost estimate does not establish a replacement payback or a suitable heating system. Keep adequate heating and follow relevant safety instructions. Ask a qualified energy adviser or installer to assess a home that cannot stay comfortably warm with the present system.

07

Use the calculator without double-counting

Start with annual household electricity and the proportion already recorded on the night register. Add a proposed heater load only if it is absent from that base. The same rule applies to an electric vehicle or dehumidifier: moving an existing load is different from adding a new one.

Enter the prices from your own bill or quote, not the example prices above, and keep them with the estimate, including region, payment method and meter arrangement. Then compare annual costs on both plans and inspect the break-even night share. That comparison is conditional on the entered usage. It cannot promise future prices, determine room heat demand or confirm how much a particular heater will charge.