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Heat Pump Running Costs

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  • Registered Users Posts: 19,943 ✭✭✭✭Cyrus


    Mine used 26 yesterday albeit near half at night rates which helps a bit



  • Registered Users Posts: 886 ✭✭✭ColemanY2K


    a glorious day, currently 8 degrees celsius outside according to the screen on the internal unit. the 8kW HP is on course to use circa 10kWh of energy today (4.8kWh used from midnight to noon so i pro rata to get ~10kWh).

    on the face of it i'm pleased as that's just €3 per day (ignoring the solar contribution) however i'm unsure its running as it should. the data from shelly is showing the heat pump coming on for 20 minutes, run for 20 or so minutes and then turn off. rinse and repeat for the 24 hour period apart for a single one hour session in the early hours when it heats up the tank.

    does this sort of schedule sound right or would it be considered short cycling? the stats are dumb and UFH is one single big loop. the call for heat is controlled by the indoor unit which has the 'ROOM' temperature set to 19 although the stats are saying anything from 21.5 to 22.5.

    🌞 7.79kWp PV System. Comprised of 4.92kWp Tilting Ground Mount + 2.87kWp @ 27°, azimuth 180°, West Waterford 🌞



  • Registered Users Posts: 2,306 ✭✭✭newhouse87


    Heat demand won't be there to run all the timeat 8deg hence hp shuts off. Short cycling is much more frequent. 6 per hour is considered problematic cycling.



  • Registered Users Posts: 886 ✭✭✭ColemanY2K


    It seems to keep the same routine no matter the temperature which I find odd but obviously works harder when it does come on as the temperature drops.

    Something to keep an eye on, thanks for the feedback.

    🌞 7.79kWp PV System. Comprised of 4.92kWp Tilting Ground Mount + 2.87kWp @ 27°, azimuth 180°, West Waterford 🌞



  • Registered Users Posts: 367 ✭✭munsterfan2


    Home assistant must have updated their energy dashboard recently, nice new visual of the data.


    Post edited by munsterfan2 on


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  • Registered Users Posts: 233 ✭✭cromelex


    Latest release.

    I need to fix something that will break when I update, but looking forward to having the ability to visualise the heat pump on that graph



  • Registered Users Posts: 886 ✭✭✭ColemanY2K


    not great for the 1 in 12 men & 1 in 200 women who, like myself, are colourblind. i wish more companies could add lettering or symbols of some sort to help differentiate charts.

    🌞 7.79kWp PV System. Comprised of 4.92kWp Tilting Ground Mount + 2.87kWp @ 27°, azimuth 180°, West Waterford 🌞



  • Registered Users Posts: 886 ✭✭✭ColemanY2K


    This is just a personal anecdote but thought it useful to share.

    All week the heat pump was ticking along at 0.6kWh or lower with the dumb stats reading a steady 21 degrees. the mother in law arrives yesterday for a short break and says to the Mrs she's a bit chilly. So I cranked up 'ROOM' temperature setting on the indoor unit from 19 to 21 degrees (the house temperature is usually a couple of degrees above the 'ROOM' setting which would bring the house up to 23 degrees).

    Last night I had a look at what shelly was recording in terms of consumption for the day. Lo and behold as soon as I made the change the HP went into overdrive. Consumption has doubled from 0.6 to 1.2kWh. It has been like that since 6pm yesterday and I presume will stay like that until the set temperature is reached.

    Moral of the story, even modest adjustments can significantly affect the performance of a heat pump ...so if you're heat pump is running like crazy then by dialing down the settings a tad may have a significant impact on the HP's performance.

    She's here till Tuesday 🥵

    🌞 7.79kWp PV System. Comprised of 4.92kWp Tilting Ground Mount + 2.87kWp @ 27°, azimuth 180°, West Waterford 🌞



  • Moderators, Home & Garden Moderators Posts: 5,960 Mod ✭✭✭✭graememk


    Interesting on how long it will take to get the slab up to the higher temperature. And then how long it stays at that temperature after it gets turned down again.



  • Registered Users Posts: 161 ✭✭johndoe11


    Yes, it makes a huge difference, if adjust the desired room as it offsets the heating curve.

    If your desired room temp is not lower than your actual, you could probably lower your flow temp a bit and get them to match up. It made quite a big difference in efficiency for me. See below from my manual , line 1 is 21c desired room temp, 4 is 24 and 5 is 18. As you can see it makes an enormous difference to the curve if it is changed. It is best to have temp matched up to reduce compressor cycles and have the optimum heating curve slope. I'm using weather compensation.




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  • Registered Users Posts: 19,943 ✭✭✭✭Cyrus


    massive difference now with heat pump usage,

    mine was less than 8kh/w yesterday incl DHW, im expecting it to lower again as i have decreased the overnight temps down stairs (had increased it to 23 degrees over night on night rate to heat the house up a little and lower usage during the day)



  • Registered Users Posts: 2,489 ✭✭✭ECO_Mental


    Decided to switch off room stats over the weekend as they werent calling for heat anyway…having them off safeguards me for when someone opens a window as they want fresh air and it turns them on for no reason. Should see my daily usage trend done to the 4-6kWh day over the next week or two hopfully.

    @Cyrus I dont know an I a believer in ramping up the heating at night before to predict the next day, what happens if the sun comes out the next day unexpectedly and heats the house up so you dont need heat and you have wasted all that energy for no reason. Better off just leaving it alone and if needs heat it will call for it.

    6.1kWp south facing, South of Cork City



  • Registered Users Posts: 886 ✭✭✭ColemanY2K


    i still have dumb stats and one single zone in my 2100 sq foot bungalow. i let mine just tick over to keep the house at a steady 21 / 22 degrees. very happy with its performance at the moment.

    for dhw and heating the heat pump has used an average of 6.25 kWh per day this month (up to close of play yesterday) or based on my current tariff if i had to buy power then it would in theory cost €1.27 per day.

    this doesn't take into account solar which has reduced the daily cost to zero for the month of April thus far. the way things are going it won't cost me anything to run between now and start of october.

    🌞 7.79kWp PV System. Comprised of 4.92kWp Tilting Ground Mount + 2.87kWp @ 27°, azimuth 180°, West Waterford 🌞



  • Registered Users Posts: 19,943 ✭✭✭✭Cyrus


    yeah normally id agree but our night rate is so cheap and when it was cold it was nice to wake up to a very warm house downstairs for not a large cost!



  • Registered Users Posts: 2,489 ✭✭✭ECO_Mental


    Yeah I suppose if you are on one of those fancy smart boost rates that 7 or 8 cent there is no harm

    6.1kWp south facing, South of Cork City



  • Registered Users Posts: 349 ✭✭andyd12


    I assume you have no actuators? Open loops everywhere?



  • Registered Users Posts: 886 ✭✭✭ColemanY2K


    the actuators on both manifolds have been removed to turn all the zones into 1.

    🌞 7.79kWp PV System. Comprised of 4.92kWp Tilting Ground Mount + 2.87kWp @ 27°, azimuth 180°, West Waterford 🌞



  • Registered Users Posts: 349 ✭✭andyd12


    As I thought, thanks.

    I am struggling with the dumb stats concept however… For example, one day its 0 degrees outside and no sunshine so no solar gain. The next day its 4 degrees outside and full sunshine so considerable solar gain. How is the system/HP sensing this kind of difference?



  • Registered Users Posts: 19,943 ✭✭✭✭Cyrus


    through the internal thermostats? or maybe im wrong, he said dumb stats, are they not linked back?



  • Registered Users Posts: 349 ✭✭andyd12


    Stats typically control actuators. I thought with the actuators removed the room stats are just a visual of the room temperature. But could be wrong. Interested to know how it's all controlled



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  • Registered Users Posts: 19,943 ✭✭✭✭Cyrus


    one stat will be controlling them (stat for zone 1) no?



  • Registered Users Posts: 886 ✭✭✭ColemanY2K


    The indoor unit has a built in stat. You set it to your preferred temperature and the HP does the rest.

    I have 2.8m wide south facing window yet the temperature remains constant so all I can say is excessive solar gain isn't an issue.

    Post edited by ColemanY2K on

    🌞 7.79kWp PV System. Comprised of 4.92kWp Tilting Ground Mount + 2.87kWp @ 27°, azimuth 180°, West Waterford 🌞



  • Registered Users Posts: 2,306 ✭✭✭newhouse87


    What tariff are you on with your electric provider?



  • Registered Users Posts: 886 ✭✭✭ColemanY2K


    flogas bwg smart electricity

    day 24 cents

    night 18 cents

    peak 28 cents

    standing charge works out at 65 cents / day.

    🌞 7.79kWp PV System. Comprised of 4.92kWp Tilting Ground Mount + 2.87kWp @ 27°, azimuth 180°, West Waterford 🌞



  • Registered Users Posts: 2,306 ✭✭✭newhouse87


    V good, tried to get it but didn't have referral code. Think for non smart you didn't need code,just rang up and no questions asked.



  • Registered Users Posts: 886 ✭✭✭ColemanY2K


    i'm probably one of the few boardsies who signed up to the bwg deal who actually works with a bwg affiliate 🤣

    🌞 7.79kWp PV System. Comprised of 4.92kWp Tilting Ground Mount + 2.87kWp @ 27°, azimuth 180°, West Waterford 🌞



  • Registered Users Posts: 349 ✭✭andyd12


    Is the preferred temperature a room temperature or HP flow temperature?



  • Registered Users Posts: 886 ✭✭✭ColemanY2K


    It's the preferred room temperature.

    I find whatever I set it to on the indoor unit the house stats report two degrees higher so in the photo below it's set to 19 degrees in order for the house to reach 21 degrees. I don't know why this is the case but it's something the plumber said would happen when he installed it and sure enough it has.

    Other photos showing current temperatures of flow etc.

    The house has been built to passive standards hence why I have a really low flow (supply line) temperature.

    🌞 7.79kWp PV System. Comprised of 4.92kWp Tilting Ground Mount + 2.87kWp @ 27°, azimuth 180°, West Waterford 🌞



  • Registered Users Posts: 1,781 ✭✭✭hold my beer


    My sitting room thermostat does somethimg similar but the opposite way. Constantly says the room is about 2 degrees warmer than it actually is. Bizarre, and very annoying.



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  • Registered Users Posts: 19,943 ✭✭✭✭Cyrus


    there is normally a calibration setting you can change (if its digital) my joule ones were 2 or 3 degrees out.



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