Help!! Air source heat pump costs

Olinda99 · 3 August 2022 at 7:08AM

It might be worth turning the pump off completely - at the 'fuse box' if possible. Then monitor your electricity meter use for 24 hours. This will confirm (or otherwise) that there is nothing else drawing power that you are unaware of ie that it is in fact the heat pump that is using it.

welshmoneylover · 3 August 2022 at 7:36AM

It’s the immersion heater for the hot water! I didn’t realise you had one when I posted earlier.

I was able to turn my CH off in January due to having a multi fuel fireplace which was on 24/7

k_man · 3 August 2022 at 8:01AM

welshmoneylover said:

It’s the immersion heater for the hot water! I didn’t realise you had one when I posted earlier.
I was able to turn my CH off in January due to having a multi fuel fireplace which was on 24/7

@MrsBeee Related to the post above, how much hot water do you use each day?
Full baths, long (more than 5 minutes) showers (assuming these are from the hot water) etc?

And how well insulated is your hot water tank?

If you are using a full tank each day, that could be up to 10kWh of your 16kWh per day.

And is the hot water/immersion on 24/7? If so that could be up to an extra 1- 2kWh.

comeandgo · 3 August 2022 at 8:05AM

I’ve had to use my immersion heater for the first time in 16 years as our oil based water heating system is on the blink. Usually our electricity use is 6 or 7 units a day. The immersion heating was on for two hours to heat the tank of water. That day our electricity use was 15 units. Never again. Will use the kettle and wash in the sink until it gets repaired.

MrsBeee · 3 August 2022 at 8:36AM

Oh wow. Thank you so much for all of your replies. I’m a little overwhelmed, what a wonderful place this is.

I am also mortified after reading the other thread about ASHP which I didn’t find previously but I will get to that in a second.

To respond:
House is a 3 bed semi, 2 bathrooms plus a toilet. System was installed during the build 15 years ago and isn’t retro fit.

The system is Daikin. It’s 15 years old. Our house is partial stone, rest brick and some rooms have full height ceilings, hence winter heating costs are high.

We don’t have a hot tub, outside lighting, fish tank, pool, pond, tumble dryer etc. I don’t use anything that I know uses a lot of electricity. I was bought up to only light the room you were in!
We have two phones, two tablets, one tv, a printer, router and extender, American fridge freezer, dishwasher, washing machine, oven, grill, induction hob and an air fryer. We don’t really drink hot drinks so the kettle isn’t boiling all day. We do have a mini coffee pod machine for guests. All appliances except the fridge were purchased new less than 4 years ago.

We have a petrol lawnmower but otherwise the garage is empty as I park my car in there. The hot water tank and ASHP system is in the garage, all pipes are lagged. We haven’t had a bath since moving in, two adults have one short shower a day, I wash my hair twice a week which takes a little longer, after which I blow dry to style.

We don’t have a separate meter for the ASHP.

So after reading the other thread and running to the garage at 6am, my hot water has been heating 24 hours a day for 2 years. I had absolutely no idea and the two engineers I’ve had out have never mentioned this, I even asked about timing the heating and hot water and we had a long conversation about it. I am almost certain he said it doesn’t really work like that and the immersion will only kick in to do the legionella cycle and if I turned it off, or heated the water less, I was at risk of legionella!!

I have now changed the settings with the help of a YouTube video (what a pain for anyone who has the old controls) and it will only heat for 1 hour per day.

I couldn’t actually be more thankful at this stage. Even if I am also completely embarrassed having spent hours researching the system, controls and efficiency and this never being mentioned. We also have weather compensation mode on, this has always been on for the person who mentioned it.

The other thread mentions EPC. If anyone is interested my EPC says I should be using 2500kwh per year for water heating. I always thought this was just widely inaccurate and the assessors based the rating on a unrealistic usage.

I will report back in a couple of days

[Deleted User] · 3 August 2022 at 8:53AM

A well-lagged hot water cylinder only has a very small heat loss each day. My 250L unvented cylinder heats as required throughout the day up to 65C. Yesterday, our energy use for cylinder re-heating was slightly less than 3kWh. Clearly, if the cylinder water temperature is low then more heating will be required to bring the cylinder up to temperature.

High energy use is clearly dependent on hot water use, and heat loss from the cylinder and associated pipe runs. I get ‘annoyed’ as we have a long pipe run to one of the basins in our home which ‘wastes’ over a bowl of water before the tap runs hot. ‘Annoyed’ in the sense that I wish there was some way that I could lag the pipes.

MrsBeee · 3 August 2022 at 9:36AM

I have amended our hot water to 48 degrees now I have set it to 1 hour per day.

We have a long way from the tank to our en suite so we never use hot water in there. We use the main bathroom for showering. This probably sounds crazy, but we have honestly done everything we can possibly think of to reduce our costs.

Evan3020 · 3 August 2022 at 9:43AM

Just keep taking regular meter readings, hourly, 2 hourly and look for spikes or whether its a constant drain.

Mstty · 3 August 2022 at 10:22AM

Edited thanks for the reply

chris_n · 3 August 2022 at 10:25AM

Your tank will be losing more heat in the garage than in the house as the temperature differential will be higher (maybe not at this time of year). Anything you can do to enclose it, e.g. build an insulated cupboard around it will help. It would be better in the house but I guess that isn t possible / practical.