Hi all,
We’re about to pay Octopus to come and give us a HP quote. The instant quote feature has said £500, but I know (from my parents’ who’ve had an Octopus install) that this won’t be the final figure. I just wanted to ask what to look out for when it comes to the survey and the quote. We have a 2018 newish build, 4 bed detached. We have 5.3kWp PV with 6kWh battery which was installed in 2019, plus a 24kWh Nissan Leaf. Currently on GCH with a Potterton Combi, flow temp set to 45, temp at rads is around 46 when measured with an infrared heat gun. We are pretty stingy and have the thermostat set to 18.5 usually, occasionally 19-20. On Octopus Intelligent and Gas Tracker. Gas usage in 2024 was 5,859kWh, electricity 5,324 (inc 2,200 EV charging), export 2,531. Total bill for the year was £69/month on average. With heatpump install plus induction hob, we want to go electric-only and try and get the bills down even further.
Heatpunk heat loss is 4.3kW at ODT of -2.8C. Current emittter output of 2.7kW. At a flow temp of 43C, Heatpunk tells me I’d basically need to switch every rad for a K2 in order to meet heat demand. Currently, we have K1s everywhere except the kitchen/diner where we have 2 P+. What I am trying to understand is how we manage currently with the K1/P+rads at 46C, when the calcs say we really shouldn’t be warm! The rad in our bedroom is only 700x450 K1.
Install location will be the utility room. We currently have tumble drier and washing machine with a cupboard in between and sink above. Boiler is above the tumbler. Plan is to remove the sink and worktop, stack the tumbler on the washer (heatpump, no vent) and the cylinder can go where the tumbler was. All pipework in place there already from the combi boiler. It’s 22mm copper initially (not sure for how long) but then we have 10mm plastic microbore to the rads. Imagine we will need a buffer. Plan is to have the heatpump at the side of the house, take some of the ceiling down (I’ll do that and make good after) in the utility and dining room and run the primary pipework to the utility that way. Joists go the correct way for this. Meter cupboard is outside on that side of the house, so easy cable run for that. Will Octopus only install HPs on the ground, or will they consider on a wall bracket? (have 2 waterbutts which I’d like to not have to move, and have HP installed above them).
Any hints of what to look out for with Octopus would be much appreciated. Will they install OEM kit if I supply it, for instance?
No they supply and install , what i would watch out for is the heat loss , it has traditionally been over egged , some times as much as double the actual heat loss
the other questions you have would be a good idea to discuss with the surveyor
another thing to watch out for would be planning permission
Thanks Chris. Install location is 6.3m from the neighbour’s property across 2 driveways, and they have no windows on that side of the house, so we’re hoping we won’t need PP.
Very likely your air changes per hour is lower then the assumed defaults, it needs a formal airtightness test to get a worthwhile heatlose calculation.
Calcs are normal based on outside temperature of -3, you are also heating the house to a significantly lower temperature then are required by British Standard for heating designs.
But Octopus designs to a flow temperature of 50c at -3, their overstated heatlose often results in a more efficient system that can run at closer to 40c at -3. Assumung weather compensation curve is adjusted by iser to lower level that gives required comfort.
they seem to have a push on their 9 kw cosy and 6 kw cosy at the moment , which i personally would not want them dont seem very efficient and dont allow customers to have access we get from the daikin systems
or they want to control your heating system
We don’t yet know how the Cosy heatpumps work in reallife as noone have a heatmeter feeding us data from one. The Cosy 6 heatpump software is being regularly updated so likely efficiency have improved since formal testing.
But cleverly Cosy 9 is better then Daikin 9kw as it have a reasonable minimal output.
30kwh of Fogstar batteries is likely to give better savings then a little higher COP from a much more costly installer.
My experience with Octopus, for a Daikin 8kw: Broadly speaking they were fine, but some schoolboy errors made when rushing to finish.
Tank thermometer wasn’t installed correctly (and wasn’t even connected!), and so the tank was overhearing and the D2 pump (which is bloody noisy!) was firing at 2am to release the pressure. Woke up the street, pretty much.
Unit settings - they just default to what Octopus tell them, but might not be right for your house. It is trial and error (see Tuning performance of Dakin 8kw Altherma 3 - #15 by divenal) but the main thing for me was the CH pump speed was set to low, which when you did the maths, meant insufficient heat output and so my house wasn’t getting warm. Now that’s been set to high, it is fine.
In relation to the above, I am playing with the weather curve and modulation settings, and TRV settings, to get my house right. At the moment (the last few days have been cold) my heating is kicking in 4 times a day. My COP is about 3 which is poor - it should be more like 3.5.
An FYI that you might find it is no cheaper than gas - it really depends on your house. I’ve got 13 kWh storage which really helps, but today (3c outside) the battery is basically empty by midday, and everything else is peak rate - I’m paying £5/day electric at the moment for a 3 bed semi, 90% of that is heating.
off typic but - Set the Madoka to 19.5 degrees 24/7 ie no schedule, no setback and a tuned WDC with modulation, our 8kW unit (4 bed 200 year old house ) uses 12kWh (~500W baseload) when on 24 hrs a day at 3 degrees outside (COP 4.25 ish), turns off as a result of solar gains, cooking, PC gaming etc takes about 6 hrs to cool down and then turns back on again
Is that gas-boiler thinking? Your heat-loss (6kW, say) is continuous, and the heat pump sized to just cover that. If it only runs a few hours a day, it cannot replace the heat lost. Gas boilers are typically way oversized, and can quickly replace the entire day’s heat loss.
100% it is gas boiler thinking. We’ve been round in a few circles; initially it was setup to run all the time by Octopus, but the house wasn’t getting warm. During that colder snap in November, the house wasn’t getting above 14C no matter what we did or how long the HP was on - cue angry wife - so Octopus came out and changed it to the “boiler mode” we have now. I think they must have adjusted the WDC too. I think that the low pump speed setting (which was commented on as “strange” by another Octopus engineer) was actually the real culprit there, as I mentioned in another thread on here. Doing the maths on that 7L/min gave me ~2.6kw heat output when it ought to be much, much more when the outdoor temp was low.
Yesterday evening, thanks to help on here, I modified various parameters and I now have the house set to 19C all the time, but I may need to use TRVs to lower bedroom & other rooms heat. This morning, the upstairs bathroom was very toasty (too toasty!) but other rooms a little colder than we’d like. I’ll see how it goes.
As I type this, the house is at 19C and the HP is pulling 2.9kw. I suspect it’ll do this all day long, electric bill be damned…
Again, this kind of stuff should be transparent to the user - it is too complex and time consuming. Gas boilers are great from a user point of view, because as you say, they dump heat into a space quickly - so why can’t a HP work out what time it needs to come on and at what temp to keep to a desired set point? Doesn’t seem like rocket science to me…! It is literally a handful of parameters that need setting and monitoring.
Join the world of HP’s and the reality of installers sticking to rigidly to the manufacturer’s settings. After 2 + years of complaining about mine to Octopus it was only when I followed advice on the Forum that I believe mine is setup as it should have been.
Change your control to LWT and adjust the WC to about 39/40c @-2 and forget the Madoka. I leave the HP running all the time @ 800/900kW (currently 761kW) for 9kW HP and the property gives me the temperatures I want.
That’s the problem. That value differs for every house. I’ve been told to set it to 40c at -15, to use setbacks (heat geeks advice), to not use setbacks, and everything in between. I will dial it in eventually, but it is very much sifting the info given and working out what is right for the property we’re in. No matter what I’ve tried, the unit doesn’t ever pull less than 2kw, and I cannot have that running 24/7. That’s unaffordable. It’s a pretty standard 3 bed semi, not a mansion…
Assuming you always want the bedrooms at the same temperature, eg you don’t need them at office temperatures in day time. Learn how to balance radator and reduce the flow of water to the bedrooms a little. There should be no need to use TRV to give a consistent relative temperature between rooms.
(A kitchen may need TRV if it get lots of heat from cooking, likewise a room that gets lots of solar gain, or bedroom used as office in daytime.)
That not possible unless there is a fault, (for example the backup heater always running). Once the flow is up to requested temperature then unit will modulate and then cycle.
We have a DT of 5 set, and you can measure the DT across the radiators with some Testo 115i clamps or a thermal camera, then turn the locksheild to influence the temps.
Hi @ebyard, something appears IMHO very wrong with your setup pulling that much power 24/7.
Well that depends on how strictly you interpret ‘never’. At the moment my system is drawing about 2kW all the time except when defrosting or off. Over the last 24 hours the mean draw was 1.55kW and the total energy was 37kWh.
It’s cold, the heat pump is a little undersized and there is fairly high heat loss.
