Solar, Heat pumps and grants

Akerfraken

JKenH said:
My suggestion would be that, if your GCH is working without problems, just leave things as they are. We are all guilty of using man maths to justify spending money but I don’t see that your energy savings (if any at all) are going to cover the cost of switching to an air to water heat pump. Your bungalow doesn’t sound ideal for a heat pump. With a house, as Mart has pointed out, what heat escapes thr

The system is designed to get rid of all our energy bills (Net). There is large array of solar panels, battery backup, Solar assisted heat pump for the hot water and an electric boiler for the central heating only, I'm happy this will meet our requirements.

My big query is that the £7.5K grant does apply to hybrid systems but they list one of the qualifying conditions is that you are replacing a fossil fuel system, which we are however it lists electric as a fossil fuel, however its my belief what they were meaning was old storage radiators or similar electric heating systems as not only are we getting rid of gas but the wood burner as well.  

Qyburn

How many kWh of gas and electricity do you use in a year?

QrizB

Akerfraken said:

My big query is that the £7.5K grant does apply to hybrid systems ...

It says on the gov.uk pages "You cannot get a grant for a hybrid heat pump system (for example a combination of gas boiler and air source heat pump)".

https://www.gov.uk/apply-boiler-upgrade-scheme/what-you-can-get
See immediately below the third bullet point.

Akerfraken

QrizB said:

It says on the gov.uk pages "You cannot get a grant for a hybrid heat pump system (for example a combination of gas boiler and air source heat pump.

Depends where you look Ofgem say they will accept hybrid systems as long as you getting rid of a fossil fuel heating system which we are, we are replacing the gas boiler for an electric boiler for heating only.

Martyn1981

I think the issue there, is that electric boilers (and for instance storage heaters) are not new technology. So they don't need pump priming via subsidies, and they don''t bring energy savings, but will of course help shift you away from FF gas as the leccy supply steadily decarbonizes.

I have to say, I really don't think you should be going down the route of a leccy boiler, it will increase your costs. Not only will it consume ~3x more leccy than a heatpump, but you will need a 2 to 3x larger battery if you hope to heat the house on stored cheap rate leccy through the day. You will also need to have a larger inverter on the storage battery, in order to meet the higher power demand of resistive heating.

If you don't want to get one or two A2A units, which work well for bungalows (trickier for multi-storey properties), then perhaps consider storage heaters* (effectively energy/heat batteries) as a way to help heat the property on cheap rate leccy.

As Qyburn has asked, knowing your gas and leccy consumption, would help here. If your heat energy demand is enormous, then that might rule out the leccy boiler and storage heaters (on cost) and A2A units on ability, but make the use of a HT ASHP viable. As after the grant contribution, its cost of install may not be too much more than a HPHW tank and leccy boiler install, and the difference made up over time by comparably reduced leccy bills.


*Edit - If you're interested, then there may be another approach, and that's something like the Tepeo heat battery. This is similar to storage heaters, in that it charges up with heat during the cheap tariff period, but then feeds the heat via an existing wet radiator CH system.

Two big problems, firstly, it's expensive, probably £8k installed, so only worth considering I suspect if the subsidy scheme is widened to include it. The company has been asking the Gov, but we won't know till the review comes out .... Spring .... Summer ..... eventually.

The second, is simply energy capacity, at only 40kWh. However, if you can pre-heat the property a bit during the cheap rate, and supplement the Tepeo during the day from your battery, then it might be enough. But I suspect from the hints you've dropped that your heating needs will be too high for this, but just wanted to mention it in case.

Akerfraken

Martyn1981 said:

I think the issue there, is that electric boilers (and for instance storage heaters) are not new technology. So they don't need pump priming via subsidies, and they don''t bring energy savings, but will of course help shift you away from FF gas as the leccy supply steadily decarbonizes.

I think people seem to be getting hung up on different bits of the proposed system, I understand that leccy combi boiler is a none starter as the running cost for hot water and CH is prohibitive and the BUS would not look at it, neither would the Solar and the SAHP it is only the combination that works, SAHP for hot water electric boiler for CH the powered by solar and battery backup. As I read it this is a hybrid system that Ofgem will look at under the BUS as it uses a HP and gets rid of a fossil fuel, in our 2 as the wood burner will go as well. It is an expensive system to install but does leave us with no energy bills and if Ofgem do approve the the grant that would be great.

In addition these are the usage figures you asked about Gas about 21000 Elec about 2300

QrizB

Akerfraken said:

As I read it this is a hybrid system

Yes.

Akerfraken said:

.. that Ofgem will look at under the BUS

No.

Akerfraken said:

 It is an expensive system to install but does leave us with no energy bills

What makes you think it will leave you with no energy bills?

Akerfraken said:

In addition these are the usage figures you asked about Gas about 21000 Elec about 2300

Assuming 4000kWh/yr for hot water (and that's probably an overestimate) you'll end up needing 17000kWh of space heating, most of that in the months of November to February when there's no appreciable solar generation.

So I'd wet-finger estimate that you'll be buying 15000kWh/yr of extra electricity to feed your electric boiler, which at current prices will be £3750 a year.

Edit to add:

You might not realise quite how little use solar panels are in the wintery third of the year. I've got almost 3kWp of solar on my roof, in a decent location in the south of England, and in a typical December they might generate 100kWh of electricity.

Your electric boiler might need 3-4000kWh of electricity in a typical December. If we take the lower of those figures, to generate 3000kWh of electricity in December you'll need 30 times more solar panel than I've got. That's 90kWp, which will set you back something like £50k. Plus you'll need 300kWh of battery to smooth it out, another £50k. So you'll be spending £100k on solar and battery in order to heat your house through the winter.

(If you bought a heat pump instead of an electric boiler, you'd only need 1/3rd of that (so still £33k) ...)

Qyburn

Does anyone really class wood as a fossil fuel?

Martyn1981

Akerfraken said:

Martyn1981 said:

I think the issue there, is that electric boilers (and for instance storage heaters) are not new technology. So they don't need pump priming via subsidies, and they don''t bring energy savings, but will of course help shift you away from FF gas as the leccy supply steadily decarbonizes.

I think people seem to be getting hung up on different bits of the proposed system, I understand that leccy combi boiler is a none starter as the running cost for hot water and CH is prohibitive and the BUS would not look at it, neither would the Solar and the SAHP it is only the combination that works, SAHP for hot water electric boiler for CH the powered by solar and battery backup. As I read it this is a hybrid system that Ofgem will look at under the BUS as it uses a HP and gets rid of a fossil fuel, in our 2 as the wood burner will go as well. It is an expensive system to install but does leave us with no energy bills and if Ofgem do approve the the grant that would be great.

In addition these are the usage figures you asked about Gas about 21000 Elec about 2300

Thank you for the info. Apologies if it has seemed like I was arguing with you, I think I miss-understood your posts. I thought you had been given an idea and wanted thoughts comments on it, rather than just sharing your approach.

My fear, which has now grown, and as explained by QrizB, is that the leccy boiler (resistive heating) will cost you more. Or if your space heating is high, which I think you've now confirmed, will cost you a fortune.

We have 8.725kWp of PV, though most of it is E/W facing so particularly poor at winter gen, and our Dec estimate for generation is 175kWh, and 200kWh for Jan. So doesn't cover our normal leccy demand, let alone contribute to space heating, DHW, nor EV charging.

We can however cover our space heating on cheap rate leccy, as we use A2A heatpumps. Between running them hard on cheap rate (11.30pm to 5.30am) then more gently 5.30am to 11.30pm on battery storage (20kWh), we manage to heat the house at ~7p/kWh (similar to gas price), but reduced further by the HP COP, so hopefully 3p/kWh(t) at those times. For you, with resistive heating, you will pay more (per kWh(t)).

I totally commend you on the HPHW tank. I'm only not going that way because of the location in the house, and the possible fan noise being an issue for the neighbours. In reality, it doesn't actually make any financial sense (for me) as our monthly gas bill is ~100kWh for oven cooking and DHW (Wifey and I take very fast showers). Taking boiler efficiency into account, as the combi will always be working from cold for our DHW, I'd guess our monthly DHW consumption at ~60kWh. So about £4 on cheap rate leccy, and even at a COP of 3, the HP could only save us ~£3 (or less) pm. Hence no financial gain for us as it would never payback, but I'd still like one.

Back to the heating, I don't know what power you need, but even if it's something that a very small and cheap boiler like a 5kW SlimJim could manage, then that's £500+, plus running a higher power cable, consumer unit changes, and install, you'd be looking at about the cost of an A2A install, say £1,500. In reality, I suspect the leccy boiler will be quite a lot bigger, and more expensive, perhaps equal to 2 or more A2A units.

Would 2 A2A units work for you - I don't know. As I mentioned, they are great for bungalows as the heat is trapped on one floor (unless you have a staircase to a dormer room?) but I appreciate that your heating demand is significantly higher than mine. [Before the use of A2A, our total gas demand was about 8k to 9k pa.] So that's where the wood burner would come in.

In reality, if your gas consumption is that high, you'd probably need an ASHP wet system, hence why I mentioned the HT (high temperature) options.

Again, if you are happy with your choice, and were simply sharing the info, whilst asking about the subsidy scheme, then I apologise for interfering. But needed to share and warn you, that PV in the UK is not a heating option, especially for resistive heating. You will pay a fortune for leccy, so worth considering other options, and possibly changes to the subsidy scheme that might come out this summer.

One chap on here, installed an A2A unit in their bungalow, was pleased, then a second, then stripped out their wet system. So maybe if you can stick with the gas boiler for a while, you might consider getting one installed, and seeing how it works (as a hybrid system for now), alongside the PV, battery and HPHW tank. Then deciding where to go next, even possibly retaining the gas boiler, but reducing it's annual consumption.

JKenH

Qyburn said:

Does anyone really class wood as a fossil fuel?

I posted my reply to this question on the Alternative Green Energy thread so as not to derail this practical discussion.

https://forums.moneysavingexpert.com/discussion/6071905/the-alternative-green-energy-thread/p149