Heat Geek were going to charge £800 for their planning stage, which seems a decent % of the overall cost of a heat pump, so I'd counted them out. Octopus and British Gas won't look at it until the extension is built. Aira did quote for us, they offered Aira Heat Pump 6kW, with the Aira Indoor Unit (All-in-one) 250L, and a Buffer Tank 40L. I decided against them because of the buffer tank and advice I've seen on here regarding that. I've asked for Ovo to contact me a couple of times, but they haven't as yet.

Are there any other companies you'd recommend?

Thanks so much - with installation and planning being such an important part of the process, I really do appreciate the input and advice!

It seems odd these companies don't design and plan for you before the build, I would say this is at least half our work load, in fact I quite like these jobs as they seem to have a 6-9 month lead in time, we also often will fit the cylinder way before the heat pump for the exact reason you mention, you need hot water sooner than heating. I find that providing you build the home to the specification, it is easier for us to desk top design from your build documents as they normally have very detailed fabric specs so no fabric assumptions on our part. If you are in Kent I would be very happy to help you.

Also worth noting if you are not in Kent and need to find someone, the Vaillant list works, we are on the Vaillant register and its right that some of us don't advertise loudly as we are already booked for a fair few months so what trickles in just keeps topping up ahead. We currently have orders and no space up to July and have planned orders in nearly every month this year and a couple next year, these much longer planned dates are all self builds secured way before ground is broken. It is defiantly a normal thing to plan, design and book once you intend to start your new build.  

I second that. The third time I tried using the Vaillant list I found one possible mid size installer - and they were happy to install Grant and Bosch as well. 

Are there any other companies you'd recommend?

I cant, but @editor probably can if you tell him roughly where you are.  

I wouldn't ignore the smaller operators in your vicinity.  I found my installer through Vaillant.  I had never heard of him and he doesn't advertise widely because he doesnt need to.  As it turned out excellent.  He was literally a one man band  - even the electrics with the exception of the power feed which had been done by an electrician in advance.  Worked long hours to get the job done and did a very neat job.  I do agree that they can be unknown quantities though so need more due diligence, but if you find a good one then they can also be very good.

Heat Geek were going to charge £800 for their planning stage, which seems a decent % of the overall cost of a heat pump, so I'd counted them out. Octopus and British Gas won't look at it until the extension is built. Aira did quote for us, they offered Aira Heat Pump 6kW, with the Aira Indoor Unit (All-in-one) 250L, and a Buffer Tank 40L. I decided against them because of the buffer tank and advice I've seen on here regarding that. I've asked for Ovo to contact me a couple of times, but they haven't as yet.

Are there any other companies you'd recommend?

Thanks so much - with installation and planning being such an important part of the process, I really do appreciate the input and advice!

Oil: Approx 1,250 litres. Bit of a guesstimate. We supplement with electric heating and kettles for hot water when the oil boiler fails (not infrequent maybe approx. 2.5 weeks in total across the past year, in fits and starts, during the winter months).

OK thats indicative more of 4kW than 7kW, although given you let the house cool a lot and use supplemental heating one might stretch it to perhaps 5kW or even 6.  7kW is a lot for a 80sq m or even a 100sq m well insulated house, mine is about double the size, 1930s, tolerably well insulated (but floors uninsulated) and 7kW. 

What Im saying is that you may well be able to get away with a good 5kW machine and if you can you may get slightly better performance (because it will modulate down further).  It might be worth getting a quote from a heat geek if you havent already, they tend to keenly spec albeit they tend to be pricy.  Also Octopus who seem almost invariably to get good reports (other than the recently introduced Cosy 12 which was/is noisy at least when first released).  Mostly I would do that to be certain you have covered all bases.

You wont want to operate your heat pump on/off, it will be very inefficient.  

With the EDF quote I would check

'heating controller' - you do not want any third party controls, this is probably just the Daikin one but check

'250L PRE PLUMBED R32 CYLINDER' - check that does not include a low loss header or a buffer tank

What flow temp are they designing for?  If >45 dont go there.

I cant speak for the Daikin controls but I can speak for the Vaillant ones which are definitely good.

You may be able to get a cheaper quote if you shop around and I believe the grant will go up shortly as you are replacing oil.  Personally I would get some more quotes.  A good technique with Vaillant (and some others) is to ask them for local certified installers.  There may be people who dont advertise because they dont need to!  Those can be a good bet.

You'd said... "If, on that basis, you want to proceed (and before we discuss the quotes) please tell us a bit more.  how much oil do you burn annually, what is your heating 'pattern', is the house basically warm all the time or do you allow it to get cold during night/day, what's the floor area of your house."

Here we go:

1. If you want to proceed...

I like the idea of a heat pump, and I'm nervous of the reality, I think partly because people have advised us against it (... aunt, mother, neighbour, oil boiler engineers) so - quite apart from any heating problems a future heat pump might serve up - it'd be very annoying to have a litany of "told you so's" as a side order. Anyway. 

2. How much oil do you burn annually...

Oil: Approx 1,250 litres. Bit of a guesstimate. We supplement with electric heating and kettles for hot water when the oil boiler fails (not infrequent maybe approx. 2.5 weeks in total across the past year, in fits and starts, during the winter months).

Electric FYI: 1st Jan 2025 - 31st Dec 2025 we used 3,248.699 kWh (and exported 1,598.19 kWh, obviously mostly in the Summer)

3. What is our heating pattern...

March to Sept - no or very limited heating through the radiators - put on a jumper if it's chilly, which isn't often. The back of our house is South facing, and if it's sunny in the morning it warms up quite quickly from that. The North facing side of the house is cooler, which is actually nice in Summer.

From Sept through the March, we've used heating as and when we've needed to, which through winter is every day. We tend to heat if the kids are with us, so early mornings, evenings, weekends, and holidays. Sometimes on an evening (esp when the kitchen is warm from cooking) we will use an electric oil radiator to heat the main room only, or very occasionally have the log burner in the main room, to avoid using the heating system too much. We work from home so winter day-time is cold, and at times we've resorted not only to socks and jumpers but coats as well.

Our oil boiler was installed in 1992. There is no thermostat, there are no thermostatic controls on the radiators in the rooms, no dials indicating 1-5 for power/heat output etc. The heating is either on, or off. The temperature of the heating is dictated by the temp of the water. We have our water temperature set at 78C at the moment. The temp we need to set it at varies, for reasons I can't quite work out, I think the boiler loses efficiency over time (?) so in-between services or repairs we've needed to increase the temperature setting to get actual hot water. We've had it set to 65 in the past, and that's the lowest it's ever 'worked' at. The boiler 'leaks' quite a lot of heat into our utility area (where it's housed), the under stairs storage where a lot of pipework is (always like a sauna despite the pipes being insulated), and our main bedroom above the utility area (mainly heat rising from below, and maybe a bit from the hot water tank which is in that room). 

4. Is the house basically warm all the time or do you allow it to get cold during night/day... we allow it to get cold. Night time - no heating, so in colder months it's cold. Winter day times - cold. 

5. What's the floor area of your house... 43 meters squared downstairs. For some reason, 36 square meters upstairs... can that be right?. There's a porch and entrance way downstairs that we don't have upstairs. Those figures are for the existing property. When we've done the two storey side extension, there will be approx 100 square meters in total across the two floors.

Just FYI, I think I could get an oil combi boiler for about £5k installed. Maybe less. I'd be paying about £1,250 a year on oil thereafter (based roughly on current prices).

I think EDF are looking most likely, because albeit OVO have quoted cheaper, they haven't actually yet spoken to me, despite a couple of requests for a call.

Thanks as ever

@colinc Much appreciated - thank you. Similarly... I asked the chap at Aira who ran through a remote quotation with us about the buffer tank, and he admitted to not really knowing why someone would want or not want one, but despite that was pretty sure they were good. 

In general they aren't and he is wrong.  End of in almost all cases. 

That said Aira are essentially vertically integrated so can actually set up the system so that a buffer tank does no harm (unlike most), and the reports here suggest that they probably do.  There is still no evidence that it does any good though even for an Aira system correctly set up.

@colinc Much appreciated - thank you. Similarly... I asked the chap at Aira who ran through a remote quotation with us about the buffer tank, and he admitted to not really knowing why someone would want or not want one, but despite that was pretty sure they were good. 

In general they aren't and he is wrong.  End of in almost all cases. 

That said Aira are essentially vertically integrated so can actually set up the system so that a buffer tank does no harm (unlike most), and the reports here suggest that they probably do.  There is still no evidence that it does any good though even for an Aira system correctly set up.

Our quotes for retrofit GF UFH, from install through to ready for the LVT 'latex' pour;  JK were actually cheaper than Wunda and Nu Heat over-floor systems. Whatever you decide, do engage your heating installer early; to ensure correct pipe sizing calcs for flow rates, heat energy requirement. etc. If your UFH installer doesn't understand about ASHP and Heating Power calculations: this is a Red Flag, find one who does. Siting the UFH manifold can be a key decision too, in terms of loops and optimal distance to/from HP. The DHW and Rad pipework size and distances also need  consideration.

We decided early on in planning to install 'glue down" LVT (not the Click variant); the same LVT throughout the GF.

Our carpet installer suggested to consider the same carpet for 1st floor, stairs and landing (not bathroom and enuite shower). Buying a roll as opposed to 'room by room' m² is a significant saving (@25% in our case). Flooring uniformity is not an issue for us. 

To be blunt: "... failing to plan is a plan to fail"

Hope that helps.