How Do Storage Heaters Work?

Charging overnight on Economy 7, storing heat in ceramic bricks, and releasing it during the day.

Last reviewed: 2026-06-27 • Reading time: 5 minutes

Storage heaters use ceramic bricks to store heat. Electric heating elements embedded in the bricks heat them overnight during Economy 7 off-peak hours (typically 00:30–07:30) at ~9p/kWh. The stored heat is released gradually during the day via convection and radiation. Modern high-heat-retention models add insulation, fans, and thermostats for better control.

The Basic Principle

Storage heaters work like a rechargeable battery for heat:

Charge overnight: Electric elements heat ceramic bricks during off-peak hours when electricity is cheap.
Store the heat: Ceramic has high heat capacity. It stays hot for 12–24 hours.
Release during the day: Heat radiates and convects from the bricks into the room.

Economy 7 Tariffs

Storage heaters are designed for Economy 7 electricity tariffs, which offer 7 hours of cheaper off-peak electricity overnight.

Off-peak hours (typical): 00:30–07:30 (times vary by supplier)
Off-peak rate: ~9p/kWh (2026)
Peak rate (rest of day): ~28p/kWh (higher than standard 24p/kWh rate)

The heater charges automatically during the off-peak window. A time switch or smart meter controls when the heater can draw power.

Old vs Modern Storage Heaters

Old storage heaters (pre-2010):

Poor insulation (heat leaks out overnight before you need it)
Manual input dial (you guess how much charge you need based on tomorrow's weather)
Manual output dial (adjusts a damper, limited effect)
Heat releases passively all day (you can't stop it once charged)

Modern high-heat-retention storage heaters (2010+):

Better insulation (20–30% more heat retained until you need it)
Programmable timers (set different charge levels for weekdays vs weekends)
Built-in thermostats (stop charging when room reaches target temperature)
Fan-assisted output (deliver heat on demand, not just passively)
Adaptive charging (some models can top up during the day if needed)

Controls Explained

Input control: Sets how much charge the heater takes overnight. Higher setting = more electricity used = more heat stored. You set this based on how cold you expect tomorrow to be.

Output control: On old heaters, this opens/closes a damper to adjust heat release speed. On modern heaters, it controls a fan that pushes stored heat into the room when you need it.

Thermostat (modern models): Measures room temperature and stops the fan when the target is reached. Prevents overheating and wasted heat.

Why They're Common in Flats

Many UK flats (especially pre-2000 builds) have storage heaters because:

No gas connection (common in high-rise blocks)
No space for a boiler and radiator pipework
Low upfront cost (£300–£500 per heater vs £2,500–£4,000 for gas central heating)
No maintenance (electric heaters have no moving parts, no annual service needed)

Full guide: Storage Heaters →

Last reviewed: 2026-06-27