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Heat Pumps - Yes/no Or Maybe...?

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#46 IronmanG


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Posted 17 November 2021 - 02:22 PM

Being devils advocate, you arent comparing like for like. If you had put 100mm + of kingspan in every room anyway the amount of oil you would have used would drop dramatically also.

#47 Magneto


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Posted 17 November 2021 - 05:36 PM

One major difference Rocketman didn't point out is that American homes by and large used forced air, not radiators. I don't know how this affects the efficiency but heat pumps have been used here for decades. In my experience they don't seem to last very long (5-8 years is not unusual) and of course they are expensive to replace plus it gets a lot colder here (well, most of the states anyway) in winter. In Kansas it's not unusual to have temps hover around -17C or worse for weeks at a time. Heat pumps do not work at those temps.


The most cost effective way to heat a home here has been forced air/gas with electric A/C. 


Since you all are talking about radiators and hot water, you must not use forced air to cool you homes then? this is strictly a heating discussion?

#48 finch661


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Posted 18 November 2021 - 09:43 AM

Being devils advocate, you arent comparing like for like. If you had put 100mm + of kingspan in every room anyway the amount of oil you would have used would drop dramatically also.

completely agree, i also replaced the old radiators with K2+ ones, which helped get the heat into the room (and the insulation helped keep the heat in).  a  good point from that is insulation is key, and at some point everyone will be forced into changing over to electric heating.   Again i can only compare to Oil, but the cost of electricity (until fairly recently), has been increasing as a steady pace, whereas oil, the price can been quite volatile.  During lockdown, the cost dropped down to 20p/l, and is now back at 55p/l.  The highest i have seen it is 80p/l.

Another big point, is that heat pumps are seen as a holy grail, and a direct swap for existing heating systems, which they are not! We were lucky to have the system designed for our house, and had the loan to pay for it (it was about £9k for the system including the new hot water tank but minus the radiators).  Quite a bit more than simply replacing an oil boiler (or gas boiler).  The big thing for me was allowing the heating system to be on all the time, which goes against how i used to run the old oil system and our gas heating system in our last house. There has been a big uptake of ASHPs up here, and most people seem happy with them.


I am not a fan of air to air, as i am not a fan of having big diffusers in each room.  I have been in a few holiday lets with them, and i never found they warmed up the house as nicely as a wet system, but thats just my opinion. 

#49 DomCr250


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Posted 01 December 2021 - 05:14 PM

I had a heat pump installed last year, and have had it running for about a year now.  Mine is an air to water, so uses the previous radiators.  Up here, we have no gas, so the option was sticking with existing oil (price varies so much), or storage heaters.  We replaced our old oil boiler (which was burning 3-4L of oil an hour) with a 9kW panasonic unit (going into a 6 bed 1960's build).  One thing i should note, is that i have been doing up my house, and as i went round each room, i installed between 100-125mm of kingspan in each outer wall. This was key, as the water flow is only 40degC.  We just leave the temp at 21degC through the day, and down to 18 during the night.  Its strange that its always on, but means the house never really has a chance to cool down, unlike the old oil system.  We have gone from 2 tanks of oil (2400L) per year (which at the current prices is £1400) down to about £550 up to today.  


Big thing is making sur that your house is well insulated, and the system is designed for your house (we were given heal calcs for each room, and basically whether the system would work for our house). As with anything, a poorly installed system will not work, which i think is where a lot of the issues are arising.  If we had a gas supply up here, i would have stuck with gas.


overall i am happy with our system.

We ended up getting the no interest loan to pay for it, and we get the RHI payments each year for 7 years

Interesting and it very illustrative of a real world install, thanks for sharing it.


2400L of oil equates to an input of 248,400KWH of energy (1L of Kerro is 10.35KWH of energy), thats what you were using to heat your house.  Now a like for like swap with no extra insulation would have resulted in a reduction by 4 times, so thats 62,100KWH of electricity (£9K a year in electricity).  You say you've only used £550 on electricity, so thats say 3,500KWH (15P a unit) or at a 4 times multiplication 14,600KHW usage.  So your insulation has reduced your energy consumption by about 94%, I'm well impressed.


So it much better to insulate extremely well and keep your existing heating system as the cost saving would have be even greater.


I'm on oil, use about the same as you, but have a big tank (Thousand gallons) - great thing is you can buy when the price is low ... like in 2020 when it was 18 pence a litre, you cannot do that with gas or electricity.  

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