Help, we have had air source heat pump fitted with solar panels and back up battery. This is our first winter with this new system and our electricity bills have tripled, we are afraid to turn the heating on. Our bill for the last 3 months is £1150 when it hasn’t been exceptionally cold. How can this be?
Air Source Heat Pump: Electricity bills have tripled since having solar installed - any advice?
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Updated on 09/10/24 by Shads_OVO
Without any more to go on this is what I suggest you do:
Turn the hot water down to 50 degrees C. Make sure you’re only heating it on a schedule, not on ‘reheat’. I heat our hot water at night during my cheap rate hours and again in the afternoon when the outside temperature is warmest. The space heating (ie radiators) won’t get any heat when the hot water cycle is running so do it at a time when you won’t notice it missing. Mine takes about 45 mins. If you have a ‘legionella’ or disinfectant’ cycle enabled you can disable it. It’s reckoned to be unnecessary in a domestic setting where you’re using and refreshing the contents of your hot water cylinder every day.
Next, rather than have the radiators on for a few hours at a time (generally an inefficient way of running a heat pump) run it at a lower temperature for longer hours. Without knowing what heat pump you have it’s a bit difficult to explain the changes you need to make. Mine is a Daikin Altherma 3 and I have a Madoka room sensor. I’ve set the controls to Weather Dependant, which means the radiators are cooler when it’s warm outside and warmer when it’s cool outside. You may have been set up with a fixed flow temperature which is not an efficient way to run it. Open all your radiator valves (the adjustable ones) fully so they all receive heat at the same time. The heat pump needs a good flow of water pumped around and there’s no benefit closing some off here and there. If that sounds extravagant then don’t worry, you’ll save by the hp running at tickover rather than having to burst into life every time a change of heat is called for, as it is currently. You can turn the overall temperature down to use less electricity rather than turn it off. This does all sound involved I know. With more info on your system I might be able to explain better how you can do all this.
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serennu wrote:
juliamc wrote:
Hmm. Not sure I agree that the heating would cost that much through the night. How are you controlling the times and temperature?
I I have a wifi hub that controls the temps in each room
Does that control the radiator valves ? What make is it ?
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Hi
In this example the owners bills have dropped significantly by having the hp.
juliamc wrote:
serennu wrote:
juliamc wrote:
Hmm. Not sure I agree that the heating would cost that much through the night. How are you controlling the times and temperature?
I I have a wifi hub that controls the temps in each room
Does that control the radiator valves ? What make is it ?
Yes Julia, it controls each rad valve, it is a Honeywell
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I thought I’d just summarise this thread to make sure I’ve got everything straight.
Can you read through all this and correct me if I’ve got anything wrong please.
You have a small 3 bedroom house in Powys, two occupants (“oldies”) with an ECO4 installation of an air source heat pump, solar and battery, installed last year, replacing the solid fuel central heating. You still have a log burner. The installers were Sprint Renewables, who also put in new radiators, plumbing and shower. Last summer you were still taking energy from the grid though you expected to generate and store sufficient for your use.
You’ve been through one winter and the last 3 months cost you £1150 which is triple your usual electricity bill. Importantly your house has not been warm enough and you have been supplementing the radiators with your log burner. The bills are not estimates: you do not have a smart meter but have sent an up-to-date reading recently. You are on the Simpler Energy tariff, ie a single rate over all 24 hours.
You have not felt confident enough to alter the settings on the new “Cape Canaveral” controls in the airing cupboard. Warm Wales (who I assume organised the installation) suggested SevernWye came to advise you but it transpired they knew nothing about your system so could not give any help at all.
You have 9 radiators though have not had them all switched on because of the large bills. You are using Honeywell wifi controls (part of the new installation?) to set the time and temperatures they run, eg two lounge rads 21 deg for 8 hours, bathroom rad 21 for 2 hours and one upstairs for 2 hours. You have a 139 litre hot water cylinder, set at 60 deg but you have since reduced that to 50 deg. You use the shower once or twice a day.
The solar inverter is a Sun Synk, (no obvious CT clamp though one should be present where the mains electricity enters the building ie close to your meter), you have now set up an online account with SunSynk, but need help to understand further.
The battery appears to be a Dyness, it is situated where it doesn’t have much space around for cooling.
The heat pump is a Vaillant VWL 105/6 A 230V S2R1 which is a 10kW unit.
The radiator controller has a Honeywell wifi hub and individual controls on each radiator valve.
Assistance from the installer recently has been: they agree with running all the radiators at 18 in the day, but suggest setting back to 12 at night. Your low daytime electricity use suggests that the solar was supplying the house. You still need a strategy for setting back at night, at the last comment you used 10 kW at night with rads set to 12 deg. You are now running the radiators at 21 deg in the day.
My recommendations:
The Vaillant has its own inbuilt control system for setting the temperature in the house. I am certain that you should not be controlling the radiators with the Honeywell wifi controls as that will use much more electricity. Your installer (or someone competent) should show you how to do this.
I think it’s quite possible that you have an oversized heat pump. You can check that with the documents you should have from your installer. If it is oversized then your installers should be made to replace it for a correctly sized one, an oversized unit means higher electricity bills.
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Just had a very quick read through the thread. Very useful advice being given.
When is the water cylinder being reheated? Is this a constant reheat when the temperature drops below a certain value or is it set to a schedule to reheat at a certain time (perhaps overnight?)?
Is there a way of checking usage on the backup or immersion heaters to make sure these are not being overly used rather than the heat pump?
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