Hi
Had a survey completed on Monday which gave a heat loss of 9,187kWh. I have been quoted for a 11kWh Daikin heat pump.
Does that seem consistent? For context its for a 5 bed detached property, built in 2004, with adequate levels of insulation (270mm in loft), 220 sqm of floor space.
They also quote consumption of around 4,000 kWh per annum, which also seems low?
Any thoughts appreciated.
Hi, welcome to the forum, and your first step on the journey to getting a heat pump!
I’m guessing you mean a heat loss of 9,187 W at design temperature, and a 11 kW heat pump?
Looking at similar sized properties on HeatpumpMonitor.org, this seems consistent with them:
This particular system in Basingstoke may be quite similar to yours and has data for the past year.
This also seems pretty reasonable.
Do you have gas usage for previous years for your property to compare against?
Hi Tim
Thanks so much for the response, you have interpreted my message correctly! Currently we have a 20 year old gas boiler which consumes around 25,000 kWh of gas each year.
The guidance provided on similar sized heat pumps is really useful.
Thanks
Harj
With an optimistic SPF of 4, the estimated 4,000 kWh of electricity will equate to about 16,000 kWh heat over the year, which is reasonable.
Assuming 70% efficiency for an old gas boiler, 25,000 kWh of gas would produce 17,500 kWh of heat. Some of that may have been used for cooking? Not too far off I’d say.
Mine is a 2001 227m2 build with an 11kW Daikin (slightly older model than the monoblock you’d get), so maybe of similar ballpark as yours.
https://heatpumpmonitor.org/system/view?id=126
The analysis shows worst it’s needed is 7.3kW at -1.7C.
Previous owners gas usage was 44,000kWh.
Our initial gas usage with some insulation fixes 26,500kWh. Second year down to 19,200kWh.
First full year of heat pump 4096kWh elec for 18,443kWh heat, 838kWh for 2300kWh hot water.
thanks @meatballs and @Timbones. This gives me some reassurance on the levels of efficiency I can expect to achieve. I was weighing up replacing the older boiler with a more efficient condensing version however the expected efficiency appears to make the HP option a no brainer, especially as I can use a smart tariff like Cozy and my solar panels & battery in the summer.
This is a key benefit of heat pumps; you can’t generate and store your own gas!
The heat pump quoted is EDLA11DA3V3 Daikin. Does anyone know when this was released? Should I push for a newer model (assuming one exists?)
A 11kW Daikin to cover a 9.2kWh heat loss sounds about right, when it’s cold the Daikin will output less than 11kW. The real question is how accurate is the 9kW heat loss, heat loss is often overestimated. However, 9kW for a 5 bed 220 m2 sounds like it’s probably not an overestimate.
Personally, I would avoid Daikin. I don’t have personal experience with them, I’ve just been following threads on this forum. It’s also very early days for the Octopus Cosy heat pump, the data I’ve seen so far does not look very promising, but I would like to see some more data before forming an opinion.
The 9,11 & 14kW Daikin units are just software derated 16kW units so while the low end modulation may be a bit pants in warmer months it will be the size you need for ~9kW of heat loss.
The only other unit is the ‘small’ one as the 4 & 6 are also just software derated 8kW units but you will only get around 7.3kW max out of them in the coldest days so not viable unless OP can suddenly insulate the house or work on air tightness.
Personally I would be looking at the newer valiant units arotherm+ as they are easily configured for cooling aas well and seems to have a better range of sizes.
Octopus do not offer them though and if you are price sensitive the octopus installs are ok and they do seem to care about the aftercare and support. Just be sure to check your radiator schedule as they have a habit of not sizing all rooms correctly and leaving some rooms oversized if the radiators are too big (leading to how bedrooms and a cool lounge for us and an unhappy lady and battered ears for me). They did fix this subsequently when I complained and gave them the correct sizings though so overall a good outcome.
Thanks for insight and guidance on the different units.
We have 19 rads and on the Octopus schedule they are changing 5.
How could I check that the sizing it correct to avoid issues after the install? After a 3.5 hours survey I was hoping they’d get it right!
Can you share any information from the detailed survey?
Have they provided you an export of the heat loss calculation?
No they have just confirmed that the heat loss is 9,187 kWh. Our house is 220sqm with 19 rads, built in 2004, 270mm insulation in loft.
Daikin are the budget solution it seems. Having struggled to get a 9kW Daikin heat pump to work well (it’s same family as the 11kW), two important aspects I recommend you check are your pipe sizes, particularly where the heat pump connects into your system; and the radiator powers at the design temperature, probably 50C.
We had the situation where all the heat was being fed via 22mm plastic elbows, quite a restriction, which would never be able to get the power into the radiator system.
In case you aren’t aware, see HeatGeek on pipe sizing and radiators; as a rule of thumb the power output of a radiator at 50C flow is half that at 70C, (the usual gas assumption), and to get best efficiency you want to be at 40C or less - that’s roughly 30% of the power at 70C.
The other aspect of the 9 to 16kW Daikins that can be annoying is that the minimum that the compressor will ramp down to is ~800W which means a power draw of ~900W with pumps etc. This gives a minimum OUTPUT power, heat, of ~4kW.
The Basingstoke daikin is probably mine. If installed by UK heat pumps. I have a very similar house to yours. 230m2 built 2000 and 9000w ish heat loss at minus 2. My 11kw monobloc is the right size for a Daikin.
You can get a scop just under 4 which will be cheaper than gas as long as you size the rads to need a max flow temp of 38c. Do not expect them to run well at 50c flow temp and minus 2.
Most of the issues with these units are mentioned above. They run well down to 3c but can have rapid defrost issues on damp winter days that limit the output to ca 7.5kw below that temp. Not a massive problem if you have a supplemental heat source for say 2 or 3 winter weeks.
There is a separate thread on my gas vs hp consumptions and costs and also another thread on the defrost issues. Overall I am fairly happy with it …say 3 out of 5. Other manufacturers seem to make better units. Setting up properly is important though and not many installers seem capable of this. There is a lot of helpul stuff already on this forum though…so you can get a decent result…but not at a high flow temp!
Colin
thanks @ColinS. I’m concerned about the issues at lower temperatures. Are you saying that they don’t work well when its 3 degrees C external temperature or lower?
ASHP sizing for Freezing Conditions
Tells the story. I dont think my 11kw daikin is unusual as it seems to work well at all other times. I just cannot reconcile what the daikin tech data says with my real experience in freezing conditions…and as it is basicly a 16kw unit it really should do much better around zero c.
Actual Costs for Heat Pump vs Natural Gas
This might be of interest too.
Heatpumps tend to work a little better when it gets below freezing, as there’s less moisture in the air. 2-3°C is more challenging due to the amount of ice forming on the coils that need to be defrosted regularly, reducing the amount of heat it can deliver. This is not likely to be a huge issue for the home, as the heatloss will be less than the 9kW required at design temp (-3°).
Thanks @ColinS I have 10 mm microbore but Octopus have assured me it should not cause an issue. We have 19 rads in the house, they propose to change 5 to larger ones.
Should I resist a buffer tank or volumizer given I have such a large volume in the system?
