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Tricia
October 4, 2023
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Roughly how much electricity is used if the gas central heating boiler is left on permanently?

  • October 4, 2023
  • 12 replies
  • 13532 views

Does anyone know roughly how much electricity is used annually if the gas central heating boiler is left on permanently, thermostatically controlled? Is there a saving to be made by switching off completely during the warmer months? 

 

Best answer by Nukecad

@Tricia@bergh 

I actually checked my gas boiler electricity draws in various running states last week, and the controller itself on mine is using 3 W with no heating running.

So that would be 0.003 x 24 x 365 = 26.28 kWh per year.

My current standard tariff rate is 27.2p per kWh.
That would give 26.28 x 0.272 = £7.15 for the year.

So turning the boiler off completely would save 59p of electricity for each month it was off.
Probably not worth worrying about, and switching it off completely for months may give issues when switching it back on. *
(Personally I can’t do that anyway because mine is a combi boiler and does the hot water).
*Note also that many boilers will self-test, and fire up and run the pump ocassionaly, so as to keep moving parts like the pump, pressure sensors, etc. from seizing up from lack of use. If they are switched off altogether then they can’t do that.

To check how much your own boiler controls are drawing when idle:

  1. Switch the heating control to off and let it cool down so that the pump is not still running.
  2. Look at the reading on your IHD.
  3. Switch the boiler off at the wall.
  4. Look at the new reading on the IHD.
  5. It should only be a couple of watts lower and that difference is how much the boiler controls were drawing.

Dont forget to turn things on again, and reset the timer clock and programming  if needed.

 

12 replies

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Nukecad
Super User
NukecadSuper User
Super User
October 6, 2023

It's a no brainer for those of us who cook with electricity. Just change when you cook and you shoud meet target. (I've been checking mine daily and have been below 6% every day this week simply by changing when I cook).

But, as some forum posts show, if you cook with gas then it's almost impossible to meet the target without actually increasing usage elsewhere. Eg start cooking with electricity outside of 4-7. With gas cooking there is just no big electricity use to “move”.

I said, Hey - Watts going on.
    B
    Super User
    BeePeeSuper User
    Super User
    October 8, 2023

    AS you know Combi boilers heat water on-demand rather than storing water for the day in the hot water tank (although some combis do have a small buffer tank). The advice to turn down your boiler thermostat is best applicable to Combi boilers for a couple of reasons.

    1) The boiler enters condensing mode below 60°C, increasing its efficiency. There is some debate as to whether Combi boilers still need to heat water to 60°C to remove Legionella since the water isn't stored it just passes through quickly flushing the bacteria out of the system, a bit like an electric shower.

    2) Whenever you use hot water, the water from the boiler/tank must reach the tap before it gets hot. When you turn the tap off the water left in the pipework is left to cool down. The hotter the water, the more heat is wasted. We do the washing up three times a day. The "trapped" volume is about 2 litres. With a water temperature of 70°C this waste around £10 p.a., at 50°C this falls to around £6.50.

    For those with a Heat Only system and a water tank, turning down the boiler thermostat has problems. If the boiler is set to 60°C then there is no way the hot water tank can reach the same temperature (there must be a temperature difference between the boiler and tank for the tank to heat). Boilers use a certain temperature hysteresis to ensure that the boiler isn't constantly switching on and off. This is probably 10°C or more. So if the boiler flow temperature exceed 60°C it will switch off and wait until the flow temperature falls below say 50°C. Hence when the tank reaches 50°C the pump will run continuously, whilst the boiler remains off, wasting electricity.

    Annually: Petrol 1315l to 442l, Electricity 3779 kWh to 2465 kWh, Gas 17,853 kWh to 9128 kWh. 20 years of monitoring and tweaking.
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