Posted by: @ian-s

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Did the initial online quote with Octopus, energy provider, requested a call but currently finding it impossible to get anyone to talk to me. Was hoping to get a rough idea of amount of energy used by their heat pumps to get an idea if it is worth increasing my solar battery storage.

Depending on your flow temperature you should get a SCOP (seasonal coefficient of performance - energy out/energy in averaged over the whole heating season) of around 4 with a good system, so on average the energy use is likely to be very roughly one quarter your gas use.  This assumes that you currently heat your house and it doesn't cool too much at any time eg overnight (a modest cooling of a degree or so because you have switched the heating off for a few hours doesn't actually make much difference to energy consumption).  If your house cools a lot for substantial parts of the day the consumption may be more than this because you usually try to operate heat pumps on 24x7 or thereabouts.   

However during the depths of winter your COP will drop as low as 3 when its very cold outside.   So if your house loss really has a loss of 6kW it will need 6kW*24h to heat =144kWh on a day when its at design temperature all day, which means you will consume about 48kWh of electricity.  A more typical mid season day will be less than half that because you will be running at a higher COP and higher outdoor temperature.

If you have even annual gas readings you can do a sense check on loss calculations and also inspect your max gas use which will tell you about likely electricity use.  If you have half hourly meter readings you can do a more sophisticated analysis by plotting against average OAT, which can, with the right conditions, give a pretty accurate readout of house loss.  The challenge with older houses that have been upgraded is that surveyors dont always take into account the upgrades and/or the u-values of the materials are not necessarily accurately known.  Also estimating the loss due to air changes can be a challenge with older houses.  This generally leads to an overestimated loss, sometimes by a factor of 2, which causes issues.  That said you aren't going to get a heat pump much smaller than 6kW anyway and if your rads are oversized it doesnt matter, you just run at a lower FT and higher COP.  The real problems come when a (say) 6kW house is estimated at (say) twice that figure and since yours is coming out at 6kW you are hopefully not in that territory.

Feel free to most more questions/ask for further explanation.

For some reason, never explained, Aria use a buffer.  However, it would also seem they know what they are doing and it doesn’t cause issues.  Probably not needed but that’s what they do.  There is a large thread on here about Aria installation worth reading.

I have 10kW of PV, 16kW battery, 8kW inverter, an EV doing around 8000m a year, 2 adults in their 60s, a heat loss measured at 7.2kW and a Cosy9.  The battery is charged at 7p overnight.  Last year we used £108 of electricity at peak rate because the battery ran out.  If I only paid off peak rate then that would cost around £27 saving £81.  However in order to do that I would have to spend £5k on additional storage.  The economics speak for themselves and, besides, due to export and battery management strategies, our overall electric bill for the year was -£7, including the EV.

Don’t worry about additional storage until you’ve been through a year of usage.

Posted by: @ian-s

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Hi

We are just starting our heat pump journey, we have a 1962 build 3 bed detached house which has the usual large windows. We did a fair amount of upgrades done when we moved in 15 years ago, re wire, replacing an old floor standing gas boiler with numerous radiator changed from poor performing ones new hot water cylinder and moving to a sealed system, A classified double glazing etc. We have solar and 10kW battery storage and run 2 ev’s.

We have had someone from ARIA to do the initial pitch, lots of videos, slideshows etc and an initial estimate subject to survey. Main concern is their design includes a buffer tank which seems a bit overkill and watching numerous YT videos question their use. Current recommendation is a 6kw outdoor unit and 250l cylinder.

Heat Geek certified installer coming on Monday to do a survey so should get an idea of heat loss and a better idea on cost over initial online estimate.

Did the initial online quote with Octopus, energy provider, requested a call but currently finding it impossible to get anyone to talk to me. Was hoping to get a rough idea of amount of energy used by their heat pumps to get an idea if it is worth increasing my solar battery storage.

Looking for any recommendations for the Reading area for us to consider as it looks like we won’t be having Octopus through the door now.

Sorry for the long intro.

Cheers

Ian

I suspect it's pretty well known now on this forum that I'm not a fan of Aira's general lack of openness an apparent keenness to mark their own homework - at least as reported back by forum members. However, their kit is basically rebadged Vaillant (which I very much respect) and so any company providing sensible figures and basing their quote around a Vaillant install is going to be delivering much the same thing - without the buffer if you choose to press the issue, which I personally would.

To ask the immediate silly question, have you tried the forum's "Find a heat pump installer" function? Reading is hardly the back of beyond so I'm sure there are likely to be several possibilities.

In addition, I know @toodles is in your neck of the woods and actively participates in Nesta's "Visit a heat pump" site. I wonder if it might be worth your while booking an appointment and having a shufty and a chat.

@majordennisbloodnok 

Thanks for your response, I have looked at the Find a heat pump installer but the companies are just showing as Emerging at this time. I will look at what you have suggested.

Cheers

Almost all of them will appear like that at the moment, @ian-s, since the service is still fairly young. The confidence score will start to show more variety as we collect more feedback. What I can say, though, is that the installer @toodles used is one of the companies listed.

I will also say that since I have mentioned @toodles in my replies I have little doubt that he'll be along sooner or later with some words of his own here.

@majordennisbloodnok I have DM’d Ian with an invitation to contact me further. Regards, Toodles.

@toodles 

Hi

Seen your DM, can’t reply at the moment as need 3 posts but I would love to see your set up and get your thoughts and advice.

Will do a few more posts.

@ian-s Look forward to making contact soon! Regards, Toodles.

After looking and numerous videos and reading loads of thoughts and comments on here as well as reading The Ultimate Guide to Heat Pumps it appears to me there is still too many wet fingers in the air, guess work and assumptions. We want to reduce our carbon footprint and having solar, battery and running 2 EV’s has done that but at the moment my confidence in heat pump installations is now very low. So for now I will continue to watch from a distance, I still have a heat geek installer doing a survey on Monday so will be interesting to get his thoughts.

Thanks all.

Have you considered keeping your FF boiler and supplementing it with an A2A heat pump (that can also provide cooling in summer). You could run it overnight on your cheap EV tariff to preheat the house and let the FF boiler take over at times electricity is more expensive. Whilst it may not immediately remove all your FF use, it may significantly reduce it whilst leaving the FF boiler for DHW and a bit of extra heat on the coldest winter days. A hybrid system, if you will.

@Ian-S, I actually think this is a pretty reasonable place to have ended up after doing a lot of research.

There is an awkward truth with heat pumps; some parts of the design are based on assumptions. Nobody can see the exact U-value of every wall or know precisely how much air leaks through an existing house without testing it, so a heat loss calculation is still a model of the property rather than a measurement of what will happen next January. That doesn’t mean it should be finger-in-the-air stuff, though. The current MCS design process is based around a proper room-by-room heat-load calculation, and a decent survey should make it fairly obvious what has actually been measured and what has had to be assumed.

I also wouldn’t let everything you’ve read on here completely destroy your confidence. Forums inevitably concentrate problems because people with systems doing what they’re supposed to do don’t tend to start threads saying “another completely uneventful Tuesday with my heat pump”. But equally, I’m not going to tell you that your concerns are misplaced, because the quality of design and installation still varies far more than I think it should, and it’s a gamble.

Your Heat Geek survey on Monday is therefore probably quite well timed. Rather than treating it as the next stage towards buying a heat pump, I’d treat it as an opportunity for them to earn your confidence.

I’d want them to show you the room-by-room heat loss, explain any important assumptions, show what your existing radiators can deliver at the proposed temperatures, tell you the design flow temperature, explain why they’ve selected that particular heat pump and talk you through what happens on the coldest design day. If there are bits of the house they’re uncertain about, I’d actually rather hear “we don’t know, so we’ve assumed X for this reason” than be presented with a suspiciously precise number.

I’ve spent the weekend editing and proofreading my new book, and the process can appear to be farcical.

If you come out of that conversation with your potential installer understanding why the system has been designed the way it has, rather than simply being handed a 7.2kW heat-loss figure and a quote, you may feel rather differently.

@Old_Scientist’s air-to-air suggestion is also a perfectly sensible alternative if you ultimately decide you’re not ready to replace the existing heating system. With your solar, battery and EV tariff, reducing fossil fuel use incrementally rather than doing everything at once isn’t failure.

But I wouldn’t make that decision tonight. 😀 You’ve done the research; now make the installer demonstrate that they’re competent.