All Activity

Makes install super easy but also makes long term maintenance hard and expensive by locking you in to the manufacturers proprietary parts (and likely approved service network). While it might be a bit more labour to install, going with off-the-shelf multiple source parts for as much of the system as possible will likely save you headaches down the line if you are someone who wants to get into the detail/wants flexibility in who you choose to do servicing. If you are completely non-technical and want to pay for the approved service/oem parts then the integrated stuff can make sense.

A 12kw heat pump for a new build is a lot. What's the size of the property? Minimum/regs insulation or a higher standard? What's the size of the existing 3-phase? I wouldn't be surprised if your overall energy estimates are pushing the DNO to overspec your needs and you couldn't just get away with sharing the existing supply with no upgrade at all. You have a lot of solar going in and if needed you could likely leverage that + batteries to offset peak demand if it's borderline. Some inverters will have a mode to allow this (ie, it will use power from the battery to limit the overall draw on the utility) and if not then there are plenty of other options if you can redirect some of the 16k into solar stuff. If the current spec is minimum insulation then bumping that to high spec might cost a few k extra but reduce energy requirements and long term bills. Not done this myself but DNOs tend to get quite concerned when you say 'workshop' and they tend to want to specify the supply to power everything at once whereas for a hobbyist/one man small business it's unlikely you use more than 2 machines at once.

Me too. Building projects can have quite a tendency for 'unplanned arisings'.

Not directly relevant or anything to do with us, but just to introduce Otter South West When we moved here (South Somerset) in Oct '25 we inherited a Daikin ASHP which we decided we'd like serviced and they are one of the local approved co's... But the point I wanted to make was that the guy Chris who came was professional, extremely knowledgeable, helpful and did a great job for us well beyond a service. If you need someone like that then you could ask them if they could help...

I had a similar initial quote and quibbled it it came down. Read up on what should and should be chargeable on the no-contestable sometimes some costs of upgrading which should not be charged to the customer are slipped in. There are some good threads here already to assist with this. For the contestable we made some really good savings doing dig and duct ourselves and then finding suitable licensed contractor for cable install and meter works. Ended up paying roughly half. All in. Not actually finished yet so there could be some surprises.

Size for heating not cooling, you will regret the higher running cost of running a oversized heat pump. UFH in screed is a huge buffer of heat and cold. If you peak cooling is 5.5kW that heat demand can be spread over many hours. Example I removed a 6kW and installed a 4kW in January this year. I was getting CoPs between 7 and 8 this summer doing cooling. This time last year doing heating my CoP 3.72 for the month, due to very light heat loads and plenty of standby hours, same house, same plumbing a CoP of 5.15 this year with the 4kW heat pump. With 192m² of UFH your volume of water is huge and would prevent short cycles. Unless you want to zone every room. Your fan coils are constant water flow and variable fan speed based on room temp. Cooling via UFH is no issue as long as you don't force 7 degs water through it. Run between 12 and 16 degs in the UFH loops you have cooling. Pre plumber cylinders are a waste of money for a heat pump as they have lots of stuff you don't need. You can spec the kit you need for under half that if you eliminate all the things you don't need. I never bothered with a grant, don't believe they should exist, they don't add value. I did it DIY. My view Direct cylinder heat via immersion. You make it smaller and heat hotter. Charge with solar an ToU tariff. Heat pump to direct to UFH to heat and cool. No buffer, house ideally a single zone, no buffer. If you are desperate for room temperature control gets an Adia Thermal. If you want fan coils get ones that run from the same flow temp that you should flow through your UFH in cooling mode

I would not double up on UFH and fan coils. In the basis heat rises and cold falls, I would fit UFH downstairs and fan coils upstairs. Assuming you only intend to heat the HW in the tank to a low temperature (for best COP) I chose 300L. No point in pre plumbed, there really is no advantage and it constricts your ability to plumb it the way you want, not someone else's idea of how to do it. Don't put the HW tank in the plant room, find (or create) a cupboard for it somewhere central to points of HW use to get the shortest runs and thus quickest time to HW out of the tap.

I'm designing the heating and cooling system for my new build. I've done the thermal modelling, and my peak heating demand is 3.7kW, peak cooling is around 5.5kW. ~190sqm of underfloor, no radiators. I'm thinking roughly this kit: Monoblock ASHP, 6-7kW. >250L DHW cylinder. Pre plumbed. >80L buffer tank Heating emitted by UFH Cooling emitted by fan coils, with insulated supply loop. Modulated by fan speed. Valves to switch between heating and cooling and prevent cold water ever entering UFH loops I plan to run most of the pipework in advance of the equipment being installed. My electrician to do all the high voltage runs ahead of time too. I will supply and fit the fan coils further down the line. I think the remaining work for the heating side will be: (1) physically installing the ASHP and hot water tank, (2) plumbing the bits together in the plant room, then (3) testing, programming and commissioning the system. I've seen kits (Stiebel Eltron has one) where the DHW, buffer tank and ASHP controller are all integrated into a single unit, which seems like it would make install even easier? Are there other kits like this? I chatted with a few MCS installers who quoted figures pushing towards £20K for supply and fit, which seems wild when so much of the work will already be done. I can spec high end kit for about £10K all-in -- and these quotes were not high end! Am I underestimating the install? What's the most cost effective way to do all this, and still get the BUS grant (if it still exists by then)?

4kW Hiaer heat pump £2050 incl VAT from Wolseley (you may need to buy an indoor unit also now). You will 2x anti freeze valves an isolated valve and couple of flex hoses. Install direct to UFH manifold. Buy a direct cylinder and just heat via immersion about £500. Any plumber can install your cylinder. About £3k for parts plus labour to install.

Is the barn yours and on the same site ? If so I do not understand why you cannot come from there. Is it worth talking to your electrician?

Hi Everyone, Received quotes back from DNO for New Build, they have come in at over 16k for single phase, 23kVA import capacity with 25kVA transformer or over 23k for 3 phase, 40kVA import capacity with 100kVA transformer. Both require a post and relevant transformers. Power lines run along one side of our plot so distance isn't a factor. Our set up will be 12Kw ASHP 21 x 510w solar panels 12Kwh back up battery Fast charge EV charger Induction Hob Small workshop Usual household appliances etc. These costs seem excessive, frustration is there is already 3phase to existing barn but we cannot use this to reduce cost according to DNO, their quote to upgrade existing transformer came in more expensive. My question is, do we go with the single phase or 3 phase given this is our only source of power and we want to future proof as much as possible? Quote between contestable and non-contestable costs are less than 1k so not sure where savings can be made.

I think the core point is that the majority of the rise in electricity prices is down to the rise in gas prices rather than "net zero"

A reasonable point. The growth in renewables since 2010 has been pretty remarkable 2010 less than 5% 2015 about 25% 2020 about 40% 2025 about 50% 2015 was when the carbon emissions from our grid really started dropping. Back then UK gas was about 35p a therm. So the rise in wholesale prices over that period is even more - so presumably the rise in electricity prices attributable to gas prices would be similarly steep.

Hi All. I am looking to have a heat pump and 250l cylinder installed in Somerset. I have had 2 heat loss calculations and two quotes. Both come to over 12k for a 4/5kw heat pump and cylinder system. The flow and return pipework is already in. UFH and manifold on the ground floor. I don't know how they can justify that cost but unless I can find an alternative I am going to have to go with it. I have already had the BUS voucher (which has expired but I am eligible). I have wasted 6 weeks while my useless plumber goes back and forth with the plumb centre and they are quoting to install a pre plumbed cylinder with a buffer tank. I absolutely don't want/need a buffer tank or zoning. I have had to take out a bridging loan to complete the build so every month wasted is costing a fortune so I am looking at all options, one of which is forgetting the BUS grant/MCS and just getting someone to get on with it, hence my question here. I am all ears if anyone can recommend an alternative course of action. The heat loss for the house is 3.2 - 3.4kw. MVHR is installed. It is a 3 bed detached new build with UFH on each floor (the first floor is yet to be done but I have a design and think I will get the builder to do this.)

I looked into this a few years back, there should be something about it posted up. Pretty sure that in the inverter data sheet it states what the minimum load is, but I really can't fully remember now. Can make running a few low wattage lights on an off grid system a bit tricky.

Having had our battery up and running for a few months I've noticed that the battery inverter seems to allow up to around 300w of power to be drawn from the grid before it starts to ramp up battery power to supply the house load. If the house is load is 200w it all comes from the grid. If the. house load is 500w, 300w comes from the grid and 200w from the battery. If this grid draw is at peak rates, which it is through the day, it adds up to £100s a year! The grid draw is roughly the same on the inverters meter on the house incomer and on the smart meter display so I think the meter and the reading displayed on the inverter are correct. Anyone come across this issue on a Solis inverter??

@Spinny thanks again, I appreciate your input from experience. We're doing quite a bit and have an architect and an initial set of requirements from the SE. It's an old building which needs some shoring up and I have no idea how they'll be tackling some parts so insurance will be vital. You've given me quite a shopping list on insurance so it is good to have time to sort this out. It's also something that I didn't include in my (very rough) costings!

Not sure using 2020 as a baseline is really helpful when talking about the cost of renewables. Go back to 2010 and the answer may be somewhat different. Though this does highlight that while there may have been past costs due to renewable policies the recent impacts are limited. It is still the case though that we have relatively high and structurally high prices. Really any discussion about prices should be holistic. I continue to believe that there are likely cheaper ways to achieve the same result

I joined Axle in the last month via a referral in this thread (thank you) Since then we've had 4 events paying about £5 each time, therefore so far had about £45 (Note to self - change to a tariff with better export rate) NICE!

Can we presume that you have asked around within the company your work for. Someone else may have already looked into this? If not, then you may get noticed as someone who is looking to improve things for the company :-) - a good thing for you

As we’re using Home Assistant we should be able to get some kind of trigger into that, which would allow us to run a Dali lighting scene that’s basically “everything on, full brightness”. I was hoping to be able to get more specific data, like the first sensor to be activated, so we could use text-to-speech to say “smoke detected in the xxxxx” across all the house speakers, but as JohnMo said above there’s a danger of overthinking this and ultimately the main objective is to enable everyone to get out quickly and safely…

I did consider using plasticiser, and would have done for render, but didn't use it for the screed, as I wasn't sure what affect it would have on a semi-dry mix. I used Mannok Master Grade cement.

https://www.carbonbrief.org/revealed-expensive-gas-behind-nearly-90-of-rise-in-uk-electricity-bills And to look at the 2nd biggest chunk of the increase - network costs.... "According to the Energy Networks Association, up to 80% of the investment in electricity grids is required to maintain existing assets, with the remainder going towards expansion for net-zero." A reminder that the backbone of the grid has a design life of around 60 and was built in the 60's. And also "Notably, household electricity prices have increased far less rapidly since the Hormuz crisis than gas bills, with higher clean-energy generation helping break the link between the two."

It looks like it. I should have added that, in principle, Cavius makes that easy as they have a cheap RF Relay (CV9004), though you'll find it here, rather than on their own site.

I'd get them to come out and do a service on your unit at the same time.