Your browser isn't supported
It looks like you're using an old web browser. To get the most out of the site and to ensure guides display correctly, we suggest upgrading your browser now. Download the latest:

Welcome to the MSE Forums

We're home to a fantastic community of MoneySavers but anyone can post. Please exercise caution & report spam, illegal, offensive or libellous posts/messages: click "report" or email forumteam@.

Search
  • FIRST POST
    • Stan79
    • By Stan79 28th Nov 17, 7:01 PM
    • 15Posts
    • 0Thanks
    Stan79
    Working out Air Source Heat Pump running cost?
    • #1
    • 28th Nov 17, 7:01 PM
    Working out Air Source Heat Pump running cost? 28th Nov 17 at 7:01 PM
    Hi all,

    Does anyone have any experience working out the running cost of an Air Source Heat Pump?

    I've been very bad at recording readings from it so only have a few readings plus the start date to calculate from... in principle though, is this equation right?

    kW used / (Days elapsed x 24hours) x tariff price per kW = cost per day

    So, last winter would be:
    2682kW / (87 days x 24 hours) x 0.21 = 0.27 per day

    And, this summer would be:
    719kW / (192 days x 24 hours) x 0.21 = 0.03 per day

    Does that look right? Many thanks in advance for any help!
Page 1
    • Cardew
    • By Cardew 28th Nov 17, 10:37 PM
    • 27,994 Posts
    • 13,844 Thanks
    Cardew
    • #2
    • 28th Nov 17, 10:37 PM
    • #2
    • 28th Nov 17, 10:37 PM
    If your ASHP used 2,682kWh in 87 days, that is an average of 30.83kWh a day and an average of 1.28kWh per hour over the whole 87 days. If you pay 21 pence for a kWh(extremely high cost) then it costs 6.47 a day and 27p an hour.
    • matelodave
    • By matelodave 28th Nov 17, 10:59 PM
    • 4,721 Posts
    • 3,045 Thanks
    matelodave
    • #3
    • 28th Nov 17, 10:59 PM
    • #3
    • 28th Nov 17, 10:59 PM
    I think we need a bit more info. Are the consumption figures you are giving for the ASHP alone or for the whole house.

    Is the ASHP on a seperate meter or have you got in on the day rate of an E7 tariff or some strange complex metering system. As Cardew says 21p a kwh is insanely high what tariff are you on. I'm moaning about having to pay 11.55p/kwh to run mine.

    My ASHP cost very little to run in the summer but iit can look quite expensive in the winter but I reckon mine uses around 3000-3500kw a year which equates to between 350 and 400 a year.

    As it responds to the house heating requirements and it has weather compensation it's consumption can vary between 10-50kwh in a day depending on how cold it is outside. That's anywhere between 1-6

    You can only determine what it's using by continuously monitoring it's consumption.
    Last edited by matelodave; 28-11-2017 at 11:03 PM.
    Never under estimate the power of stupid people in large numbers
    • Stan79
    • By Stan79 28th Nov 17, 11:01 PM
    • 15 Posts
    • 0 Thanks
    Stan79
    • #4
    • 28th Nov 17, 11:01 PM
    • #4
    • 28th Nov 17, 11:01 PM
    Hi there,

    The 2682 figure is just a kW figure.... not a kWh figure!

    Stan
    • Stan79
    • By Stan79 28th Nov 17, 11:06 PM
    • 15 Posts
    • 0 Thanks
    Stan79
    • #5
    • 28th Nov 17, 11:06 PM
    • #5
    • 28th Nov 17, 11:06 PM
    The figures given are for the heat pump only.
    I'm on a Superdeal/Flexiplus setup where there are three tariff prices:
    Day @ 20.77p / kWh
    Night @ 10.99p / kWh
    Stored heat @ 9.92p / kWh

    Storage heaters heat the old part of the house and a new extension has a wet underfloor setup powered by the ASHP
    Last edited by Stan79; 28-11-2017 at 11:08 PM.
    • Stan79
    • By Stan79 28th Nov 17, 11:11 PM
    • 15 Posts
    • 0 Thanks
    Stan79
    • #6
    • 28th Nov 17, 11:11 PM
    • #6
    • 28th Nov 17, 11:11 PM
    The usage figure i'm quoting is the kW used by the heat pump. Not kWh.
    • matelodave
    • By matelodave 29th Nov 17, 9:00 AM
    • 4,721 Posts
    • 3,045 Thanks
    matelodave
    • #7
    • 29th Nov 17, 9:00 AM
    • #7
    • 29th Nov 17, 9:00 AM
    Energy consumed by the heatpump will be measured in kwh, ie if it uses 1kw and it's on for one hour then it's used 1kwh. Your leccy meter measures in kwh

    Heat energy produced by the heatpump is also measured in kwh and is done by using a heat meter which measures the temperature of the water going into the heatpump, the temperature of the water leaving the heatpump and the volume of water flowing through the pump. These are integrated together which results in the quantity of heat produced by the pump.

    The COP of the heatpump is ithe difference between the energy supplied to the heatpump from the electricity supply and the heat energy output from it. So if it consumes 1kwh of leccy and produces 3.2kwh of heat it has a COP of 3.2.

    The quantity of energy produced by the heatpump varies with the outside temperature and the flow temperatures so isn't a constant.

    Most heatpump COPs are spec'd at 7 degrees ambient to 35 degrees flow (7/35) and a change to either of those temperrtures will result in a different COP.

    If you assume that your heatpump has a COP of 3 then your 2682kwh of leccy should have produced about 8000kwh of heat which means you are paying the equivalent of around 7p/kwh during the day and about 3,6p/kwh at night assuming you get some benefit from using it from the off-peak supply.

    I'm interested in how you are measuring the consumption - is it separately metered on it's own circuit, indepenedant from everything else or have you got an energy monitor connected to it?
    Last edited by matelodave; 29-11-2017 at 11:15 AM.
    Never under estimate the power of stupid people in large numbers
    • Cardew
    • By Cardew 29th Nov 17, 9:35 AM
    • 27,994 Posts
    • 13,844 Thanks
    Cardew
    • #8
    • 29th Nov 17, 9:35 AM
    • #8
    • 29th Nov 17, 9:35 AM
    Hi there,

    The 2682 figure is just a kW figure.... not a kWh figure!

    Stan
    Originally posted by Stan79
    Believe me the figure of 2,682 used over 87 days is kWh!

    Your heat pump could be rated at anything between 9kW and 14kW

    As said above, the price you are paying for electricity is unbelievably high. There are plenty of tariffs available where you pay around 12p/kWh to13pkWh all day and night i.e. 24/7, and that includes all the electricity consumed in the house - not just for the ASHP.
    Last edited by Cardew; 29-11-2017 at 9:40 AM.
    • Stan79
    • By Stan79 29th Nov 17, 6:53 PM
    • 15 Posts
    • 0 Thanks
    Stan79
    • #9
    • 29th Nov 17, 6:53 PM
    • #9
    • 29th Nov 17, 6:53 PM
    Ah... i've found part of the problem... The meter i have been quoting is a meter linked to the RHI payments and measures the amount of hot water produced in kW. What a prat. Sorry to waste your time.

    Still no closer to working out how much electricity the heat pump is consuming!!!

    Changed tariff today and am now paying 16p day, 8.5p night, 7p stored/heat. Works out to 200 saving based on projection and cheaper than their lowest single rate tariff. Projected bill is 726 for a family of 4 in a 4 bed house.


    As i say though, I'm still no closer to working out how much electricity the heat pump is consuming!!!

    It's a 10kW model...
    • matelodave
    • By matelodave 29th Nov 17, 7:32 PM
    • 4,721 Posts
    • 3,045 Thanks
    matelodave
    If you are having to provide meter readings to get RHI then you should have two meters, one is the heat meter which works out how much energy your unit is producing and you should also have a separate electricity meter to record how much electricity you are inputting. so your RHI should be based on the difference between the two
    Never under estimate the power of stupid people in large numbers
    • Stan79
    • By Stan79 29th Nov 17, 11:02 PM
    • 15 Posts
    • 0 Thanks
    Stan79
    I don't have to provide meter readings. I think the fitters installed it "just in case"...

    Unless the control box for the heat pump logs kWh usage? I will have to have a look!
    • matelodave
    • By matelodave 30th Nov 17, 8:31 AM
    • 4,721 Posts
    • 3,045 Thanks
    matelodave
    Ttis is what I've got www.energyhive.com/dashboard/dave which allows me to monitor my energy consumption. You can monitor it on a PC, phone or tablet and download the data if you wish

    There's a similar device made by Efergy (The Efergy Engage which seems to use similar software and the same servers) Maplins are flogging them off cheaply at the moment, if you can find any left in their stores. 20 for a hub and transmitter. https://www.maplin.co.uk/p/efergy-engage-hub-kit-n67nw

    Mine is monitoring the whole house, but as I've had it for several years I've got a pretty good idea of how to read it so I know what's on and when and most of it is for the heating at this time of the year.

    It's possible to get extra transmitters to monitor different circuits. The sensors clamp around the supply cables so there's no requirement to make connections to the mains supply/ Although if you wanted to monitor just one device, like your heatpump, you'd have to clamp it round the live conductor in the cable that feeds it.
    Last edited by matelodave; 30-11-2017 at 8:40 AM.
    Never under estimate the power of stupid people in large numbers
    • Cardew
    • By Cardew 30th Nov 17, 11:02 AM
    • 27,994 Posts
    • 13,844 Thanks
    Cardew
    If you are having to provide meter readings to get RHI then you should have two meters, one is the heat meter which works out how much energy your unit is producing and you should also have a separate electricity meter to record how much electricity you are inputting. so your RHI should be based on the difference between the two
    Originally posted by matelodave
    Hi,
    I must admit to knowing little about the detail of RHI payments, but I cannot see how you can have a heat meter to measure energy the ASHP is producing.

    Even if a meter could measure the energy produced, what is the relevance of the figures obtained? If you and I have identical houses and ASHPs yet I am wasteful and use twice as much 'energy' as yourself, would I get twice the RHI payments? If not what is the point of measuring the energy produced?

    From: https://www.ofgem.gov.uk/system/files/docs/2017/10/essentialguideforapplicants_rpiia_4.1_october_2017 .pdf

    Most people won’t need to install meters to join the
    Domestic RHI and will be paid based on the annual
    heat demand figure listed on their EPC,
    My 'back of a fag packet' understanding of the RHI system for ASHP was was that the heating/hot water demand of the house was assessed by EPC - say 15,000kWh - and the COP(SPF) was assessed by MCS - say 3.0 - and the RHI payments were based on those assessed figures.
    Last edited by Cardew; 30-11-2017 at 11:06 AM.
    • sam108
    • By sam108 30th Jan 19, 11:21 AM
    • 3 Posts
    • 0 Thanks
    sam108
    Air source heay pump excessive electrcity bill help
    HI,
    We just installed an ASHP which replaced an old combi boiler.
    It is used for domestic hot water and heating.
    We have the old radiators which are used.

    Our last bill for the month came to around 700.

    I have now started to monitor the electricty usage of the ASHP as it has an electrcal meter fitted. It is using around 100KwH a day.....

    This is around 470 per month just to run the ASHP for elecricity usage....

    Can someone help? IS this normal?

    Its a 4 bed detached house, temperature is set at 22 but never gets above 19.5 at the moment

    BUt my biggest worry is the huge electricity bill per month 500 is almost another mortgage....

    I checked online and most are saying that the average running cost should be around 1100 per year.....but we are looking at almost 6k running costs

    Any help or direction most appreciated?
    Maybe the intsaller has not set this up right

    many thanks
    sam
    • lovesgshp
    • By lovesgshp 30th Jan 19, 3:15 PM
    • 1,357 Posts
    • 748 Thanks
    lovesgshp
    You should be looking at a lot lower cost for that. I will presume you are using radiators.
    You need to check all the pump settings .....flow... cutoff ...etc. It could be a installer error and also the pump operates continuously even with no heat demand.
    Give us the pump model, size of house and we may be able to provide more help.
    As Manuel says in Fawlty Towers: " I Know Nothing"
    • sam108
    • By sam108 30th Jan 19, 3:28 PM
    • 3 Posts
    • 0 Thanks
    sam108
    Hi Lovesghp,

    Thanks for your reply- model is Samsung Air To Water Heatpump Monoblock 16kw model AE160JXYDEH

    House is 4 bed detached; 3000sq feet

    using radiators which were there before with combi boiler

    I've checked with installer and he says this is normal (but surely 100kwh is way overboard?) - or am i missing something....
    • matelodave
    • By matelodave 30th Jan 19, 4:11 PM
    • 4,721 Posts
    • 3,045 Thanks
    matelodave
    What is your heating flow temperature and what temperature is your hot water.

    IMO it's never a good idea to just bung a heatpump onto an existing system because the radiators are seldom sized to allow the pump to run at it's optimum temperatures - ie between about 35-45degrees. Anything over about 50 degrees will require the use of the boost or back-up heater which will be using peak rates electricity.

    What controls have you got? and what are they set to, what timings. If you are trying to run it like your old boiler with a couple of hours in the morning and a couple at night then it will be flogging it's heart out and you'll still be cold.

    It took me my first winter to get it tweaked properly but our system was matched to the heatpump rather than just bunging one on in place of a boiler. Our flow temperatures are between 30-40 degrees unless it's everso cold when they might creep up to 42. Our hot water is also just heated 45 degrees but boosted to 60 degrees to sterilse the tank once a week.

    We dont turn our heating off, just down by 3 degrees overnight and then back up in the morning - we are at home all day so it runs virtually continuously at this time if the year.

    Have a look at the link in post#12 above to see how our energy consumption varies and you can see the unit runs at night as well.

    I can get through between40-60kwh a day in this weather but my overall average consumption for this January will be around 1100kwh (about 35kwh/day)which is what I expect. That's all our energy including generous use of the washing machine, tumble dryer, dishwasher, cooking etc etc. Our worst January was in 2013 when we used 1500kwh (nearly 48kwh.day).

    Our detached bungalow is about 1350sq.ft but it's roof is pretty big, however it got lots of insulation u there (over 300mm) the walls are brick with some insulation in them and the windows were double glazed in 1999
    Last edited by matelodave; 30-01-2019 at 4:29 PM.
    Never under estimate the power of stupid people in large numbers
    • matelodave
    • By matelodave 30th Jan 19, 5:42 PM
    • 4,721 Posts
    • 3,045 Thanks
    matelodave
    Check out post#15 on this thread - dunno if it affects yours

    https://forums.moneysavingexpert.com/showthread.php?p=75394313#post75394313
    Never under estimate the power of stupid people in large numbers
    • Cardew
    • By Cardew 30th Jan 19, 7:07 PM
    • 27,994 Posts
    • 13,844 Thanks
    Cardew
    HI,


    I have now started to monitor the electricty usage of the ASHP as it has an electrcal meter fitted. It is using around 100KwH a day.....

    This is around 470 per month just to run the ASHP for elecricity usage....


    sam
    Originally posted by sam108


    Are you sure that the heat pump is not using the 'back up' internal immersion heater for much of the time?
    • lovesgshp
    • By lovesgshp 30th Jan 19, 7:31 PM
    • 1,357 Posts
    • 748 Thanks
    lovesgshp
    I think as Cardew says that the backup heater is activating. Do not use the system as a normal heating system with on /off controls. They are not meant for that. 3C rad temp minus overnight for rads.
    Have you a menu to say what the power distribution is ?
    Last edited by lovesgshp; 30-01-2019 at 7:34 PM.
    As Manuel says in Fawlty Towers: " I Know Nothing"
Welcome to our new Forum!

Our aim is to save you money quickly and easily. We hope you like it!

Forum Team Contact us

Live Stats

267Posts Today

3,451Users online

Martin's Twitter