Fit a timer to economy 7 water heater

Yes, in principle a suitable timer can normally be fitted, but it needs to be selected and wired correctly for the type of immersion heater and tariff arrangement. With Economy 7 systems, the off-peak supply is often controlled by the meter or teleswitch, so the timer may lose power when the E7 supply switches off unless the correct type of timer or wiring arrangement is used.

A timer can sometimes be fitted to the daytime/boost supply instead, but it should not be used in a way that defeats the intended Economy 7 operation or overloads the circuit. The electrician would need to check the two supplies, immersion heater ratings, existing switches, cable sizes and protective devices before confirming the best option.

In most cases, the safe solution is either a suitable immersion heater timer designed for Economy 7 use, or a properly rated timer/contactor arrangement installed by a qualified electrician.

Yes, it is possible. A timer with battery backup or a permanently powered timer can be used to control the Economy 7 circuit. The exact solution depends on how the heater is wired.
I would recommend having an electrician inspect the installation and advise on the most suitable timer arrangement.

If the timer is fitted in the E7 feed it will lose power when off?peak ends, so a basic timer will stop/lose its settings unless it has battery reserve, and that’s why you’re being told it “won’t work”; however, the idea can be made to work either by fitting a battery?backed timer (or controller) in the E7 circuit that keeps time when E7 is off, or by using a (contactor/relay setup) where the timer is powered from the 24?hour/day supply but only switches the E7 supply to the heater via the contactor—what you can’t do is simply “borrow” the daytime feed to power a timer and directly switch/interconnect the E7 supply because that risks (back?feeding and mixing peak/off?peak circuits), which is unsafe and can breach metering/segregation requirements; whether it’s practical depends on your meter/teleswitch arrangement and how the two feeds/neutrals are configured, so it needs an electrician to verify the setup before choosing the right method.

You need a SmartSolution!
Yes, this can be achieved by fitting a smart switch and setting when you want to turn it on and off. It needs to handle the power of your water heater. Do you have wifi signal where the heater is?

You can fit the timer to the day time feed but can’t control the water heater via the E7 feed as it will only have power in the night.

This can be done.
Timeclocks with Economy 7 battery back up are available.

control a contactor or relay that allows E7 power to flow to the immersion heater during selected off-peak hours.
Components involved:
1. Timer (mains powered from day-rate supply)
2. Contactor/relay (rated for the immersion load, typically 16–20A or more)
3. E7 power routed through the contactor to the immersion heater
How it works:
• The timer is powered 24/7 from the daytime circuit.
• It sends a signal to the contactor only during selected off-peak hours.
• The contactor allows the E7 power to flow to the immersion heater only during your chosen time window, within the E7 active period.
Key Benefits:
• The timer keeps time correctly because it's always powered.
• You still benefit from the E7 tariff.
• You avoid heating water for the entire E7 window if you don’t need to.

Hi, yes it could be fitted to the daytime feed, although the off peak supply will be automatically controlled by whatever is switching it on so to speak [smart meter etc]. there are special timers to do what you wish, but need a 24hr supply as you ask. Dave