@technogeek I fear we do not know how ignorant we are! 😉 Toodles.

We moved into a house with an electric boiler nearly two years ago, shortly before electricity prices rocketed. Since then, I've been trying to get a heat pump installed and have had four companies quote, including Octopus. Octopus offered an "instant fixed price quote with no strings attached", the actual wording on their website. After the survey the design team 'failed' the application based on heat loss calculations, saying that a 14kW unit would not be sufficient to heat the house. I have had two other companies MCS surveys recommend a 12kW unit. 

I am convinced that the sales process casts a wide net, and throws back a lot of the catch. I put this to Octopus, explaining that real Octopuses are predatory night hunters. They didn't comment on that. 

We are still facing a cold and high carbon winter. Now British Gas are saying we need planning permission for a 12kW unit. Nobody can get planning permission in Bristol, unless they are a major housing developer. There's no heat pump revolution going on in our house. 

Posted by: @pablito

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Now British Gas are saying we need planning permission for a 12kW unit. Nobody can get planning permission in Bristol...

@jamespa thanks for the useful information on size limits. Unfortunately I'm limited to what British Gas will offer. 
My comment on planning in Bristol was borne out of frustration. I paid my deposit eight months ago, and British Gas only told me this today. Bristol City Council's planning department has been put into special measures for failing to respond to applications in a timely manner. I was told today that an application would be three to four months, and I can't wait that so will be getting quotes for a gas boiler. The sentiment of the original article is what drove me to write. 

Posted by: @pablito

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After the survey the design team 'failed' the application based on heat loss calculations, saying that a 14kW unit would not be sufficient to heat the house. I have had two other companies MCS surveys recommend a 12kW unit.

There is certainly something different about the Octopus process. My Octopus survey, as I’ve mentioned elsewhere, suggested a heat loss of 14300w and therefore a 14w heat pump - which Octopus do not supply. This heat loss calculation is 35% higher than an independent contractor who carried out a survey last year and who recommended a 12w HP.
i got EDF to carry out a survey last week and they calculated a heat loss of 11300w, 17% higher than the independent but 20% lower than Octopus - and recommended a 12w high temperature HP. However the EDF quote is quite a bit higher than Octopus.
I’ve pointed this out to the Octopus team who have agreed to look for errors in their calculations but they will not come back and resurvey. Not sure where this leaves me. I still want a HP but it’s hard to make a decision when there is so much variation in what should be a (more or less) replicable process.
 

@ivanopinion In October last year British Gas quoted for a 14kW Daikin, then revised their quote to a 12kW Valiant Arotherm plus in November. Their most recent quote was last week, also the Valiant. Octopus quoted for a 14kW Daikin, but pulled out due to heat loss exceeding the capacity of the unit.

Posted by: @davesoa

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Not sure where this leaves me. I still want a HP but it’s hard to make a decision when there is so much variation in what should be a (more or less) replicable process.

 

Unfortunately sizing heat pumps for a retrofit is very far from a replicable process because the engineer must make assumptions about the fabric which generally cannot be verified.  Infiltration loss (air changes per hour) is, it appears, frequently overestimated but other incorrect assumptions are also possible.   Many installers err towards oversizing because a cold house (due to undersizing) results in call outs, whereas an inefficient heat pump (a likely result of oversizing) doesn't.

Personally I think that a measured figure should be used to sense check, or even as the primary determinant.  14kW is a big loss (but of course you may have a big/lossy house).  How much energy does your boiler use annually/can you get the usage data/how big what construction/where is your property.

This article talks about the various options for determining the actual heat loss  https://energy-stats.uk/what-size-heat-pump/   If you have any measured data from consumption I would test the spreadsheets against it.

As a point of comparison quotes for my house went as high as 16kW (based on a 3 hr survey).  The measured and verified loss is actually 7.5kW.

@jamespa That’s a really interesting article. I’m a hostage to fortune with Octopus as computer says No. I don’t believe my house heat loss is as they calculate but their algorithm is not to be argued with it seems even though my gas and electricity consumption (supplied by Octopus) is known. 

Posted by: @davesoa

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@jamespa That’s a really interesting article. I’m a hostage to fortune with Octopus as computer says No. I don’t believe my house heat loss is as they calculate but their algorithm is not to be argued with it seems even though my gas and electricity consumption (supplied by Octopus) is known. 

Most mcs contractors I have encountered refuse to take into account measured data, but there are exceptions.  Oversized heat pumps can be inefficient.  If you have measured data I would a) use it if only to sense check and b) persist until you find someone to play ball.  You really don't want a heat pump that is oversized by a factor of 2 (I'm not saying 12-14kW is oversized, I don't know because you haven't posted any info,  but most of the installers I contacted, including two who did 3 hrs surveys, wanted to oversize the pump for my house by a factor of 1,5-2 so I do know that this can happen).

@jamespa And here is an interesting presentation from Heat Geeks on the subject:

Regards, Toodles
 

@jamespa My actual gas usage is 16500kwh & electricity 3500kwh. My survey assumed a heat demand of 19200kwh. So a heat loss of 14300w? It can’t be. I watched the Heat Geek video mentioned by @toodles above. Fascinating (and worrying) at the same time. I also visited the Heat Geek site which suggests a heat loss of 8.2kw