Help!! Air source heat pump costs

victor2

MrsBeee said:

We’ll it hasn’t gone to plan so far.
usage yesterday 17.42kwh
usage Tuesday with the immersion on 24h 16.63kwh!! 

As already suggested, switch off your ASHP for a while, preferably all day, and see what your usage is.

If you are using an additional "unexplained" 10kWh every day, that's equivalent to a constant load of just over 400 watts.

I was the person with an American fridge/freezer using about 3kWh per day before it died and was replaced with a much more efficient one. They don't draw a steady current, but cycle the compressor on and off as required, and frost free ones usually have a heating element that comes on periodically. My old fridge/freezer had an 800W element that came on once a day for about 20 minutes. However, I doubt if your fridge/freezer is the cause of your high usage, more likely the heat pump, so concentrate on that.

Alnat1

I also reported on my old American FF that was using almost 900kWh/yr (based on 48 hour Tapo monitoring) which is 2.45kWh a day average. Replaced with new upright FF, in last 30 days (constant monitoring) has used 12.5kWh, that's 152kWh/yr. Winner!!

Although new FF will take several years to see ROI 

Evan3020

Wow! 900 kwh will soon be £450 a year to run.

Mstty

The OP here states their Fridge Freezer uses 2.9kWh a day so that's over £480 a year come October or £40 a month!! Just for a fridge freezer.

matelodave

Here's my fourpence worth - we have a 140m2 detached bungalow out in the Cambridgshire fens, so pretty exposed to both wind and rain. The heatpump is a 12 year old Daikin split feeding underfloor heating all over. and a 200litre hot water tank.

 We are at home all day and so the heating runs almost continuously during the winter. We shower once a day each but can manage it in only 2-3 minutes each (including hair washing) and we heat the water to 45 degrees. WE have stuff like computers, monitors, router, separate tall upright fridge and freezer, induction hob, fan over and various other odds and sods running during the day. We also have a 55" LED TV, Skybox and 5.1 surround sound system which is used for about 3 hours a night.

Our leccy consumption is about 7-8kwh/day at the moment, but can go up to between 10 12 depending use of the washingmachine, dishwasher and tumble dryer. Most of our stuff is tumble dried rather than being hung on the line. Last week were were on holiday and most stuff was off except the freezer, Sky box, router, surveillance cameras and couple of LED timed lights and anything we've forgotten and we used around 2.9kwh a day (about 128 watts)
Our average annual consumption (over 12 years of data) is 7200kwh, but last year is was over 8000kwh as it was colder in the spring and we didn't go away as often.

The heat pump has weather compensation set so heat the flow to 40 degrees when its zero outside and linearly reduced it to around 30 when its 15 degrees and so averaged around 35 degrees. We dont turn it off over night when heating, just reduce the flow temp by 3 degrees.

It does have a parasitic load of around 120 watts, so gets shut off completely  and just turned on for for water heating at this time of the year and we can get away with heating the water every other day for an hour or using using just under 1kwh. The heatpump has a 6kw boost heater and theres's a 3kw immersion heater in the tank - both are shut off so they cant be inadvertently triggered.

In the winter we've peaked at around 55kwh on very cold days but overall our average consumption is 20kwh a day. I shall probably have a bit of a tweak of the settings to see if we can shave a bit more off but I've got no chance of persuading my wife to reduce to the house temp or using the tumble dryer less.

matelodave

It's got height but no upstairs, so unlike a house where any heat that rises from the ground floor helps heat upstairs, ours goes up and out through  ceiling into the 140m2 roof  space. Although there's about 400mm of insulation the roof area ,is still quite a bit larger more than that of a normal house.

We do have pre 2000 double glazing and some dubious cavity wall insulation which was installed when it was built in 1986 but the place is very exposed to the elements on all four sides.

Flight3287462

OP one quick question, do you have instant hot water at the tap (ie hot water circulates so you don't have to wait for it to warm up)?  If so that will be expensive, so can you switch of the recirculation pump if you do indeed have it fitted?

We have GSHP installed in our 3 bed self build 11 years ago our usage is around 9,500KW per annum and in the winter can be about +30KW/day, through the summer we use about 12-15KW/day.  Two of us working from home and 18 year old daughter PCs running constantly, induction hob, router, NASS drive, sky box, 2 x TVs, washing machine seems to be on everyday (god knows why), No tumble dryer.

Spoonie_Turtle

matelodave said:

It does have a parasitic load of around 120 watts, so gets shut off completely  and just turned on for for water heating at this time of the year and we can get away with heating the water every other day for an hour or using using just under 1kwh. 

How exactly do you do that?  With the settings at the boiler(? Water tank? I don't know what it's actually called), or the big red button by the outside unit?

matelodave

I have three heavy duty switches on the wall - one feeds the heatpump, one the boost heater and one for the immersion heat. I keep the boost and immersion heater ones off (unless I want a hot water boost or a higher tank temperature) and just turn the heatpump one on when I want hot water heating- it does lose the clock time and day but all the other  programmed stuff stays in memory. I'm not too fussed about legionella sterilisation as its a non-vented tank fed directly from the mains which is quite highly chlorinated (smells like a swimming pool and tea tastes horrible unless filtered) so I just do it once or twice a month, rather than weekly.

They each have a  separate feed from MCB's in the original off-peak consumer unit - 32a for the heatpump, 32a for the boost heater and 16a for the immersion. The bungalow used to have storage heaters which had a  separate MCB to each heater. So I've use three of these and up rated the cable for the 32a feeds. We don't have E7 anymore so the peak and off-peak units are paralleled at the meter (I got it done when we had the meter changed to single rate)

I only do it between about May and September when the outside temp is above 15 degrees or so, I lleave it on for the rest of the year and just let the heatpump get on with it. The clever thing to do would be to fit a big time switch to save doing it manually

MrsBeee

Lots of replies again so please prompt me if I miss anything. 

Matelodave - your home size and ASHP set up sounds identical to ours although we have some full height rooms. Our windows and doors are wooden but double glazed. 

We don’t have the same buttons you do, and no boost option at all. I can only turn off the boiler on the boiler or at the fuse. 

I would love to get down to your usage levels. 

Todays usage is on 11kw so far at 9pm. I haven’t done a wash load today and we’re both late back so only just cooking and then will sit down for an hour of tv. 

We do have a recirculating pump which provides instant hot water but I turned that off months ago. I saw very little effect on the use. I have been monitoring everything since we had a smart meter fitted, I came here when I felt I could reduce no further without stopping hot showers and hot meals! 

I feel like my usage is comical and in some ways unbelievable. We don’t even use the lights unless absolutely necessary, don’t use hot water in the bathroom furthest from the tank. Always wash on eco, don’t tumble dry, don’t have anything typically expensive to run, yet our usage is this high. 

I am going to turn off the ASHP one day this weekend to monitor usage. 

Whilst my fridge is obviously a problem, it would take a long time to see the benefit from a more energy efficient replacement. We could replace with a smaller type but it’s old and working and I am inclined to keep it for the time being. It would sell for nothing and probably doesn’t have long left.