What are Economy 7 hours and how do they work?

Economy 7 is a UK dual-tariff electricity metering arrangement that provides seven hours of cheaper electricity overnight, typically between midnight and 7 am (though the exact window varies by region and supplier). Storage heaters use this window to charge up with heat at the lower rate, then release it during the day at no additional electricity cost.

Why is my storage heater warm in the morning but cold by afternoon?

The heater has used up its overnight charge. Either the input control was set too low the previous night (so it did not store enough heat), the output dial was turned up too high (releasing heat too quickly), or the heater itself is old and has lost insulation efficiency. Try increasing the input setting on the coldest nights and reducing the output dial in the morning.

Can I replace my storage heaters myself?

Removing and replacing like-for-like storage heaters in the same position, on the same dedicated Economy 7 circuit, is possible for a competent homeowner if you understand the wiring. However, the Economy 7 circuit uses dedicated wiring and a separate meter that is different from your standard ring circuit. Any new circuit, new cable run, or consumer unit work is notifiable under Part P and must be done by a registered electrician.

My storage heater circuit trips at night. What should I check?

First check the Economy 7 MCB at the consumer unit and reset it if it has tripped. If it trips repeatedly during the overnight charging period, one of the heaters on that circuit likely has a faulty element drawing too much current. Unplug or isolate each heater in turn to identify the faulty unit, then call an electrician to replace the element or the heater.

Understand Your Economy 7 Storage Heaters (UK)

Helpful video reference. This guide uses John Ward's tutorial "Understanding your Economy 7 storage heater" as the video reference. John Ward (jwflame) is a retired UK electrician based in Dorset whose channel is one of the most reliable sources of UK-specific electrical explanations online. His walk-through of how the Economy 7 tariff, dedicated circuit and heater controls all fit together is well worth watching before adjusting anything.

Before you start. Storage heaters are connected to a dedicated Economy 7 circuit, which is separate from your normal ring circuits. Never attempt to re-wire, move, or add to the Economy 7 circuit yourself: it has its own meter, its own MCB in the consumer unit, and sometimes its own separate cutout. Any electrical work on the circuit is for a qualified electrician. Adjusting the controls on the heater itself requires no electrical knowledge and is what this guide covers.

1. How the Economy 7 circuit works

Economy 7 is a dual-tariff metering arrangement used across the UK. Your electricity meter records consumption on two separate registers: the normal daytime rate and a cheaper off-peak rate that applies for seven hours overnight (usually midnight to 7 am, though the exact window varies by region and supplier).

The storage heaters in your home are wired on a completely separate circuit from your normal ring circuits. That circuit connects through its own MCB in the consumer unit and is energised by the meter only during the off-peak window. The heaters cannot draw power outside those hours: the circuit is simply switched off by the meter.

In some older installations, a separate contactor (a large relay) sits between the meter and the heater circuit. It closes at the start of the off-peak period and opens again when cheap-rate electricity ends. If that contactor fails, the heaters will not charge even if the MCB is healthy.

2. The two controls on your heater

Most UK storage heaters have two controls, sometimes labelled differently depending on manufacturer, but the function is the same:

Input (also called Charge): Controls how much heat the heater stores during the overnight charging period. Setting it higher means the heater draws more electricity during the off-peak window and stores more heat in its ceramic bricks. Setting it lower means a smaller charge and less heat available the next day.
Output (also called Boost or Heat): Controls the rate at which stored heat is released into the room. Turning it up increases airflow over the heat store and warms the room faster, but depletes the stored charge sooner.

These two controls are the first thing to adjust when a heater seems to be performing poorly. Most problems come down to the input being too low for a cold night, or the output being left too high and draining the charge by lunchtime.

3. Setting the input for the coming night

Check the weather forecast before you go to bed. If it will be cold the next day, turn the input up to around three-quarters or maximum. If it will be mild, reduce it to avoid overcharging the heater and running up an unnecessary bill.

Some heaters have an automatic charge control that adjusts input based on the outdoor temperature. If yours has one, it still benefits from a manual override on very cold nights.

4. Managing the output through the day

Turn the output down in the morning and only increase it when you need warmth. This spreads the stored heat across the day rather than exhausting it by midday. Many households leave the output at one-quarter or one-third until early afternoon, then increase it as the evening approaches.

If a heater has a window or boost facility, that draws electricity at the standard daytime rate to supplement the stored heat. Use it sparingly: it is the most expensive way to heat the room.

5. Confirm your Economy 7 off-peak hours

The charging window is not the same everywhere. It depends on your network distribution area and your supplier. Ring your electricity supplier or check your meter to confirm the exact hours. If you are on a smart meter, your supplier may be able to tell you precisely when your off-peak period runs.

Some older Horstmann or Sunvic time switches in the meter cupboard control the overnight window locally. If yours is set incorrectly (perhaps after a clock change), the heaters may be charging at peak-rate hours or not at all.

6. Common faults and what they usually mean

Heater warm in the morning, cold by mid-afternoon: The charge was used up too quickly. Reduce the output dial in the morning and increase the input setting the previous night.

Heater still cold after the overnight period: Check the Economy 7 MCB at the consumer unit. If it has tripped, reset it and monitor. If it trips again overnight, one of the heaters likely has a faulty element: call an electrician.

Heater very hot but not warming the room: The output control may be turned to zero, trapping heat inside. Turn up the output. If the heater is extremely hot to the touch on its casing (not just warm), the internal thermostat may have failed: switch the heater off at the wall and call an electrician.

Heater not charging at all, MCB healthy: Possible contactor failure in older installations. This is an electrical fault that needs a qualified electrician.

Stop and call an electrician if: the Economy 7 MCB trips repeatedly overnight; any heater is extremely hot to the touch on its outer casing; you can smell burning from the heater or the back of it; the wiring at the back of the heater looks damaged, corroded or has been interfered with; or any heater sparks or makes a crackling noise. Storage heater elements can fail and draw fault currents. Do not keep resetting a circuit that trips repeatedly.

When to call us

Adjusting the controls costs nothing. Diagnosing a faulty element, replacing a contactor or re-wiring any part of the Economy 7 circuit needs a qualified electrician. Richard covers storage heater electrical faults in Sandwich and east Kent.

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Richard diagnoses storage heater and Economy 7 circuit faults on the small-job rate. Call or message to book.

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Understand your Economy 7 storage heaters