SBMS

We are in the process of getting mains electric to our site and are deciding between single phase and 3 phase. I am trying to work out the max current draw of our designated ASHP - a Nibe F2040-12. It has in its technical docs a max operating current of 23 Amps - Heat Pump 22 Amps - Compressor Does this mean the unit could draw 45 Amps or am I mis-interpreting?

Does a PV array to give a return on investment for offsetting ASHP electricity costs? A large proportion of running time will be when it’s dark so probably only a few hours offset with a PV array. Could use batteries but again, how many years before payback? I’ve heard that PV array costs have gone up with latest chip supply issues as well. It’s something I discounted when researching as I couldn’t make the maths work. But if electricity costs keep increasing maybe it makes more sense?

Generally you sign up to a supplier for 24 months and they transfer ownership of the tank to themselves. At that point only they can fill it. Once the term ends you are free to find another supplier and the process happens again.

Great source of what’s currently out there: https://forums.moneysavingexpert.com/discussion/1003291/bulk-lpg-cheapest-suppliers-supply-route/p381 Current fix price contracts are hovering around 40ppl. My parents are on 38ppl with a 4ppl surcharge due to rising prices to 42ppl (extragas, north west).

Interesting! How about nibe? We’ve been recommended them by our installer.

True, but ecodan/vaillant/nibe ~12kw variants aren’t. I often wonder what the difference between a 2500 and a 5000 ASHP is…

Is 11% adoption across Europe significant?

As I mentioned on a previous thread… a good 12kw ASHP is 4K+ (Nibe or similar). Unvented cylinder - 1k. 100l buffer - £500. Controllers and pipe work £250. I would argue this is a much more realistic price for a diy install. That doesn’t have a 7 year warranty. I’ve been quoted 11k for a Nibe install. With a 5k voucher the end cost is less than I could DIY install. That’s for a good, branded, warrantied ASHP mind, not a 2k eBay one.

I think you’ve probably hit the nail on the head here. I guess it’s more than just the economics of it, and comes down to balancing the type of house we want to build, predicting future energy costs and how much we dedicate to greener technology.

Agreed, I guess it’s like all things - the greater the demand, the cheaper the supply. And they are still a minority technology that isn’t deployed at the same scale as traditional boilers. So I guess one way to shortcut mass market deployment is to subsidise. The same cycle is happening with electric cars - more expensive technology is being subsidised by the government with a target ban date of the old technology (ICE vehicles). In the EV market it’s pushing mainstream adoption of electric vehicles - which pushes private companies to innovate and scale up and bring the cost down. Same thing will no doubt happen with ASHP but someone (government) needs to nudge behaviour to create the demand.

Agreed that there are bad apples. Wait for big players like octopus to do ASHP installs (they have invested massively in training thousands of engineers in readiness) and are gearing up this year for mass market installs at close the the price of a gas boiler. Now that’s a market force that will really correct the behaviour of SOME installers over charging.

I think the problem is that most people buy based on economic factors. The fact remains that an air source heat pump (at least a good one), buffer, and cylinder costs a lot more than a cheap combi. So economically there is no incentive for the average purchaser. It’s a different game when we are talking on his forum, as self builders, that generally are not as economically constrained and want the ‘best’ not necessarily the cheapest. One could argue the scheme shouldn’t benefit self builders who could afford an ASHP and probably don’t need the grant to make their decision. But I suspect that of the 450million being provided in grants, the number provided to self builders is vanishingly small. My parents for example, living in a well insulated new build with a combi boiler have zero incentive to swap to ASHP or renewable heating - without a grant. In actual fact the problem is that the market has set the price - and hydrocarbon based heating is way cheaper. Market forces often encourage the opposite behaviour that we might want. I can say this as someone who is absolutely being driven by this force! Do I go for the, ostensibly ‘cheaper’ solution - and stick a gas system in or do the ‘right’ thing and choose greener heating. Well the decision becomes much easier knowing that the capital outlay is nearly balanced between both with a £5k voucher. Were it not for increasing electricity costs it would be a no brainier for me at this point to go ASHP. Like all things self build it’s probably not as massive a decision as I think it is, but I find myself agonising over these elements of my build!

If you have a look at page 33 of the previous document the government response states: “We maintain that hybrid systems – a system comprising of a heat pump and fossil fuel boiler – will not be eligible for the Boiler Upgrade Scheme.”

Hybrid systems aren’t eligible for the Boiler Upgrade Scheme.

I believe the consultation closed last year and the government response confirming the scheme published here in October: https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1026446/clean-heat-grant-government-response.pdf

Hi @crispy_wafer at present the main incentive seems to be the Boiler Upgrade Scheme which offers a 5k grant for ASHP installation. It kicks off in March and is replacing the renewable heat incentive scheme.

Sorry @JamesP - just found your blog and have seen what you built. U-value makeup not dis-similar to our targets although we are brick and block so may not be as air tight. Just on your figures - " 21000 kWh delivered and 3700 kWh consumed for DHW and heating" - is that 21k kWh total for ASHP heating and hot water, with your Solar PV generating everything except 3700 kWh (i.e. your solar array met 17300 kWh??)

Thanks for this. What insulation did you use and what was your measured air tightness.? Any MVHR?

Owned by tank supplier so standing annual charge of £70.

Nearby supplier provide tank for free. Groundworker a day to dig so few hundred for install. Good LPG boiler around 2500 installed.

it’s a fair point re the tank but most can be sunk underground. Its definitely an over estimate re heat requirement (it’s 260 sq m the house) and we are hoping for lower, but I guess the question was not so much about how to reduce bills with added insulation but how the two energy solutions compare. Might be a relevant question as well for a lot of rural properties with LPG being sold the benefits of ASHP. If electric prices keep rising it gets more difficult to justify. Find it strange that LPG hasn’t risen at same rate as mains gas…

I thought I would resurrect this topic, following the recent increases in the price cap, to canvas opinion.. We're about to start work on our self-build next month, so still within time to decide/change our heating solution. And I must say it's really difficult at present prices to justify the additional benefit of ASHP. I do think it's a bit more of a philosophical decision at times, but wanted to get people's opinions on off-grid LPG vs ASHP. We are estimating a heat demand of circa 16k kWh per annum, and with the predicted cap unit price of electricity estimated to increase to £0.28ppl (https://www.ofgem.gov.uk/check-if-energy-price-cap-affects-you) from April, this is how the numbers are coming out (space heating only, not included DHW) ASHP Total Average heat input 16,839 Electricity ppu £0.28 Efficiency 3.5 Total required kwh 4,811 Total annual electricity cost £1,347.14 Average monthly electricity heating cost £112.26 LPG LPG Price ppl £0.40 KwH Per litre 7.08 Boiler Efficiency 0.9 Required heat input after efficiency loss 18,710 Litres required 2,643 Total annual LPG cost £1,057.08 Average monthly heating cost £88.09 % Saving 21.53% Difficult to justify on a financial basis at present (I've not even included capital costs to install ASHP). Still very much wanting to go this route. I want to 'bet' that electricity will come back down - or that the levy on electricity will be reduced - or that LPG will go up, but a 21% cost delta is quite a difference. Thoughts?

Moved original post to new thread:

Can you explain how the cooling function works? I’ve never really understood it! I’m guessing it cools the water in the UFH and brings the slab temperature down? Does this also work in the upstairs radiators?

How do you find the Nibe? Was there any particular reason you went for this model?