Why is My Electricity Bill so Expensive? Ground Source Heat Pump with Immersion Heater

8 October 2021
by Ben Saunders

I have a ground source heat pump at my rented property and when it was being installed I was told you still leave my immersion heater on all the time. I have searched Google but I cannot find any information on if this is correct.

I have no clue how it is set up but surely I want to use the ground source energy to heat my water and turn on the immersion if I need a boost. Or is the system clever enough to only turn on the immersion when it requires it and uses the ground source normally?

I am only asking as I am currently trying to find the reason why my electric bill is so expensive, my fixed tariff runs out next month and my proposed new tariff is extremely scary when it shows my expected monthly costs of £358 on a standard tariff and £450 on a fixed. I'm currently trying to find out what is costing me so much so I can sort it.

The house is a big converted barn and not overly efficient but I still cannot understand the costs here. Anyone that can help would be greatly appreciated!

One Answer

  1. Nigel Griffiths says:

    Hi Ben,

    This was very poor advice you received. It is far better to use the GSHP (ground source heat pump) to provide your hot water as this should on average cost 1/3 of the cost of electrical resistance heating (immersion heater) thanks to the coefficient of performance of the heat pump.

    Converted barns are not normally the type of property that I’d advise using a heat pump in, as it is very difficult to achieve a complete thermal envelope and thus minimise heat demand.

    Turn off the immersion and, depending on the temperature you have set your DHW thermostat, only use it for periodic legionella disinfection.

    Depending on how the building has been insulated and your heat distribution system, predictive timing on the GSHP controls (to anticipate occupation patterns) could also reduce your use of space heating.

    Best regards – Nigel Griffiths (Build It Sustainability Expert)

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