Solar, Heat pumps and grants

Reed_Richards

If you think about why it is cold in winter you should come to realise why your proposed system will not work.  It is cold in winter because the days are short, the sun is low in the sky and it is often cloudy.  So we get much less warmth from the sun and your panels will generate much less solar power in winter compared to summer.  But winter is precisely when you need the most solar power or heating.

Akerfraken

Reed_Richards said:

If you think about why it is cold in winter you should come to realise why your proposed system will not work.  It is cold in winter because the days are short, the sun is low in the sky and it is often cloudy.  So we get much less warmth from the sun and your panels will generate much less solar power in winter compared to summer.  But winter is precisely when you need the most solar power or heating.

I think I know what winters are like I have lived through rather a lot of them. The system has been designed to produce a lot more power than we will use through the good months want to guess where it’s going. As I have said before the system has been designed to be net zero over 12 months, so yes we will be taking power from the grid in winter, which by the way are getting warmer I think it’s something to do with climate change.

Akerfraken

Martyn1981 said:

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 

No apologies necessary I probably didn’t make it clear. From the start of the discussion with the contractor it was made clear that the only way we would proceed was that the system was net zero over 12 month period and get rid of the gas. Having large roof space on South,East and West and having our usage figures this is the system they have come up with I understand it is optimised through an app (isn’t everything). And the boiler controlled by my existing Honeywell Evo home system which I have found to be excellent.On reading it was my idea that we may qualify for the grant by having the SAHP but only if it was all done at the same time including the leccy boiler making it a hybrid system with a HP and get rid of a fossil fuel. On further reading on the net Ofgem have said they will consider hybrid systems. We haven’t heard back from them yet but if do accept it it would be a nice bonus.

Just a bit extra the contractors who normally do solar panels and SAHP didn’t think about the grant as they don’t usually do the boilers, the people who make the boiler who incidentally also make HP new their boilers didn’t qualify for grant and had never thought about the possibility of installing at same time as their HP.

I do realise there are a limited number of properties where this system would work but I do wish more firms would look at an overall thing rather than, we do solar, we do ASHPs, we do boilers instead of we will look at everything and come with best solution.

Martyn1981

Akerfraken said:

Martyn1981 said:

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 

No apologies necessary I probably didn’t make it clear. From the start of the discussion with the contractor it was made clear that the only way we would proceed was that the system was net zero over 12 month period and get rid of the gas. Having large roof space on South,East and West and having our usage figures this is the system they have come up with I understand it is optimised through an app (isn’t everything). And the boiler controlled by my existing Honeywell Evo home system which I have found to be excellent.On reading it was my idea that we may qualify for the grant by having the SAHP but only if it was all done at the same time including the leccy boiler making it a hybrid system with a HP and get rid of a fossil fuel. On further reading on the net Ofgem have said they will consider hybrid systems. We haven’t heard back from them yet but if do accept it it would be a nice bonus.

Just a bit extra the contractors who normally do solar panels and SAHP didn’t think about the grant as they don’t usually do the boilers, the people who make the boiler who incidentally also make HP new their boilers didn’t qualify for grant and had never thought about the possibility of installing at same time as their HP.

I do realise there are a limited number of properties where this system would work but I do wish more firms would look at an overall thing rather than, we do solar, we do ASHPs, we do boilers instead of we will look at everything and come with best solution.

I think the key thing here from all contributors, certainly myself, is that it can't be net zero over 12 months. You mention 21,000 kWh gas and 2,300kWh leccy, so:

Let's say the DHW is 5,000kWh as a guess, and the HPHW tank reduces that to 2,000kWh leccy,
the remaining gas for space heating is 16,000kWh, and the leccy boiler being ~100% efficient reduces that to say 14,000kWh,
plus the current leccy demand of 2,300kWh,
gives us a grand total of ~18,300kWh.

To generate that over a year, you will need approx 18kWp of PV panels facing South. You mention S, E & W roofs, so let's say 21kWp, to allow for lower generation of E & W, so ~7kWp on each roof.

That's a huge system, possible if you have a really large roof, but I'm guessing it's not that big? It will also need to be 3phase, I can't see the DNO allowing anything close to that on single phase?

Is the PV system really that big?

My concern (and I think others), is that you may be being mislead on this, certainly the move to a resistive leccy boiler, which ...... dare I say ...... is probably the worst solution.

Any chance you could advise on the size of the PV system, the leccy boiler power and cost, and any other relevant info you may have, just to quell my fears?

If it was me, I'd get an A2A unit to run alongside the gas, see how that helps, and also wait for the home heating review to see what changes are made*. Crucially, if the leccy boiler/install (and HPHW tank) is going to be expensive, then including the grant, a high temperature ASHP wet system utilising your existing rads, may be a similar cost. But much lower cost to run.


* For instance, but totally made up example - let's say a full ASHP is too tricky for you, but the grant scheme extends to support the Tepeo heat battery (40kWh(t)) (or similar). Then that (under subsidy), plus two A2A units and the HPHW tank, plus the PV battery, might mean you can run the heating entirely on cheap rate leccy. Whereas the resistive boiler is (I have to say) guaranteed to draw day rate leccy, unless you have a simply massive PV battery.

QrizB

Martyn1981's 21kWp solar PV system would get you to net zero energy consumption, but it won't get you to net zero cost since "net metering" isn't a thing. You'll still be paying to import electricity on the winter, and this won't be fully offset by revenue from exporting in the summer.

Martyn1981 said:

 For instance, but totally made up example - let's say a full ASHP is too tricky for you, but the grant scheme extends to support the Tepeo heat battery (40kWh(t)) (or similar). Then that (under subsidy), plus two A2A units and the HPHW tank, plus the PV battery, might mean you can run the heating entirely on cheap rate leccy. Whereas the resistive boiler is (I have to say) guaranteed to draw day rate leccy, unless you have a simply massive PV battery.

To meet his daily winter heat demand I think the OP would need three 40kWh(T) Tepeo ZEBs. That's £25k or so? This too will need a three phase connection.

Martyn1981

QrizB said:

Martyn1981's 21kWp solar PV system would get you to net zero energy consumption, but it won't get you to net zero cost since "net metering" isn't a thing. You'll still be paying to import electricity on the winter, and this won't be fully offset by revenue from exporting in the summer.

Martyn1981 said:

 For instance, but totally made up example - let's say a full ASHP is too tricky for you, but the grant scheme extends to support the Tepeo heat battery (40kWh(t)) (or similar). Then that (under subsidy), plus two A2A units and the HPHW tank, plus the PV battery, might mean you can run the heating entirely on cheap rate leccy. Whereas the resistive boiler is (I have to say) guaranteed to draw day rate leccy, unless you have a simply massive PV battery.

To meet his daily winter heat demand I think the OP would need three 40kWh(T) Tepeo ZEBs. That's £25k or so? This too will need a three phase connection.

Yep, that's why I said plus two A2A units. So let's say, just as a guess, the Tepeo is £8k, plus £2k for the HPHW tank, plus £3k for two A2A units, less the £7.5k grant, and you get to £5.5k, which I suspect is less than the cost of the leccy boiler and HPHW tank install?

Of course, that's just an example, and only if the Tepeo and similar solutions get some sort of subsidy support, which they may well not. Similar, such as storage heaters, which is what the Tepeo is a glorified version of.

None of the solutions are simple nor easy, but I'm pretty sure the leccy boiler is the worst possible solution, and the most expensive due to day rate leccy consumption.

Qyburn

QrizB said:

Martyn1981's 21kWp solar PV system would get you to net zero energy consumption, but it won't get you to net zero cost since "net metering" isn't a thing. You'll still be paying to import electricity on the winter, and this won't be fully offset by revenue from exporting in the summer.

If he has a compatible battery, Intelligent Octopus Flux offers the same price for import and export, so pretty much net metering.

QrizB

Qyburn said:

QrizB said:

Martyn1981's 21kWp solar PV system would get you to net zero energy consumption, but it won't get you to net zero cost since "net metering" isn't a thing. You'll still be paying to import electricity on the winter, and this won't be fully offset by revenue from exporting in the summer.

If he has a compatible battery, Intelligent Octopus Flux offers the same price for import and export, so pretty much net metering.

I briefly thought about that and decided it might not be that simple!

It would need some modelling to see how the time & tariff of general compares with the time & tariff of consumption some months later.

Reed_Richards

Qyburn said:

QrizB said:

Martyn1981's 21kWp solar PV system would get you to net zero energy consumption, but it won't get you to net zero cost since "net metering" isn't a thing. You'll still be paying to import electricity on the winter, and this won't be fully offset by revenue from exporting in the summer.

If he has a compatible battery, Intelligent Octopus Flux offers the same price for import and export, so pretty much net metering.

I read the Octopus page on Intelligent Octopus Flux https://octopus.energy/smart/intelligent-octopus-flux/ .  I can't see anything there that commits to charging the same for import and export.  Is that a commitment made in the T&Cs when you sign-up or is it just how things are at the moment?

Qyburn

It's mentioned in one of their blurbs, but I guess that's not necessarily a commitment.

"Overnight & day time charging. Your battery will charge up using the greenest and cheapest energy - some of this will come from your solar and some from the grid. We will also export any excess solar if it's sunny. Your matched import and export unit rates mean your bill will be unaffected by whether your battery is charged from solar or whether you solar supports the grid and the battery charges overnight instead."

Current rates match..