Solar Panel and Battery options for very high energy use family.

Reed_Richards

You're right @QrizB , I didn't read that next line carefully enough. But I still think it worth stating explicitly that the actual energy consumption was 14,801 kWh in a year. Factors of 10 matter.

Martyn1981

Initial thoughts, are that you have a great front roof, especially as the chimneys are set back. Not sure you want to use the 'second' south facing roof, due to shading from the front roof and chimneys, but at the same time, I think one row of panels on there (near the top) may be OK.

If you are allowed to put a huge amount of PV on the property, depending on the limits the DNO (distribution network operator) set, and batteries to help buffer then I do have an additional strange idea, use the west facing walls?

First off, I don't think it will be worth it, nothing wrong with west (or east facing roofs), but steep pitched wall mounted, probably not good if off-south. I only mention it as I think the walls (cream and brick) are just off due west (+86d based on your -4d main roof?) and that's a lot of potential area, unless tree shading, and pic suggests there may be a lot.

Probably only confused everyone with that waffle. So, big front roof, looks like you can put a great amount on, maybe a row on the second roof, if it's worth you going even bigger.

Screwdriva

Thanks for sharing those images - a few additional questions/ thoughts:

On Solar:

1) Did the installer(s) who visited suggest installing 12 X 500W panels on this South aspect roof? 

2) Did they also consider this roof for another 3-4 panels? It appears to be West facing, which should give you a nice evening boost. Hopefully it measures longer than 2100mm and is over 4500mm wide to accommodate the panels?

If an installer can only fit 12-15 panels, then your best option is to go with a Eurener 515W Bifacial panel to maximize generation. Yes, bifacial panels do outperform monofacial panels on roofs. 

Given your consumption, I recommend the Tesla PW3 with a expansion pack for 27 kW of storage. The cost for this entire system should be ~£14.5K, less the £750 Tesla Rebate, fully installed. This includes a 10 year workmanship warranty, bird netting and G99 application.

On Heating:

As others have shared, electric underfloor heating is one the most expensive ways to heat a property (Frankly, I'd disable that system permanently if it were my home)

The most cost effective way to heat multiple areas of your property appears to be a Multi Split Air to Air Heat pump, like the Toshiba Haori. This would replace electric UFH, the oil boiler and anything else really in upto 5 rooms. The beauty of this type system is the best in class heating efficiency it delivers, and it's far less disruptive than ripping everything out for a wet heating system. And as of 2025, is eligible for a £2500 BUS grant.

For hot water, you could get a heat pump integrated hot water cylinder. My vote goes to the Mixergy iHp.

The combination should dramatically reduce your electricity consumption while improving comfort levels in parts of your property.

Hope this helps!

michaels

We use about 26k kWh pa so I wouldn't call 14k high usage.…

However we generate about 3.5k kWh from panels, using about 2k of this but the big win is we have up to about 75kwh of battery storage to call on so our annual import bill is below £2k with some SEG to offset.

Screwdriva

https://forums.moneysavingexpert.com/discussion/comment/81954047#Comment_81954047

Out of the 250+ properties I've helped with Solar, less than a dozen consume over 13K kWh per year. There's high and in your case and few others, super high :)

samkellylou

https://forums.moneysavingexpert.com/discussion/comment/81953827#Comment_81953827

https://forums.moneysavingexpert.com/discussion/comment/81953827#Comment_81953827

Hi  Screwdriva- Thanks for getting back to me, 

1. No the 12 panels were split between the first roof and second roof but doesn't give me the breakdown as not stated in their quote document although there is a proportion of the second roof/ valley that connects the two pitched roofs together.
2. no consideration to the shed roof and you are correct it is west facing , they only considered the shed to site the battery etc. 

Thank you for the honest price and equipment spec this will be useful to know when we have two local companies coming to visit next week. 

 

I don’t have the option to disconnect the UFH as it’s the only heat source in that part of the build and connects to a hallway that has no heating options. 

I’m afraid my budget doesn’t allow for replacing boiler with air heat pump, would this also not increase by electric usage further and how do they compare in housed that have no insulation ? 

Screwdriva

I'll let Air to Air heat pump owners comment on that one. Paging @Martyn1981

Martyn1981

https://forums.moneysavingexpert.com/discussion/comment/81956136#Comment_81956136

Cheers mate, nice and easy one that! 😂

Cue long delay whilst I ponder and waffle (for a change).

Martyn1981

https://forums.moneysavingexpert.com/discussion/comment/81956126#Comment_81956126

Hi Sam?

First off, you mention charging an EV, and having two leccy rates, so I'm going to assume that your night rate isn't too much, may I ask how much? I say this, because whilst resistive electrical heating is expensive, if you only heat the UFH during the night rate period, it may well be comparable with gas heating costs. Especially as UFH is a great way to steadily heat a property?

Now the fun bit, A2A (air to air heat pumps). These are sometimes thought of or referred to as air con units, and if any of this seems patronising, I'm just being thorough to avoid any confusion. If you need, or really want air con, then that helps massively, but even if you don't, a huge benefit of an A2A unitis that you can heat a room, or larger area, with high efficiency. You can get about 3x as much heat energy out as the leccy energy you put in, just like the swimming pool unit.

So with spare PV, or cheap night rate, you can reduce the amount of gas needed to heat the property. I progressed through 3 phases, firstly using excess PV, when I had no export income, to heat part of the house during early Spring and Autumn. Next, and now with 2 units, I started to pre-heat the house overnight on cheap rate (having moved to dual rate tariff after getting an EV). Then thirdly, after realising how powerful the units were, and getting batteries, I started heating the house only with the two A2A units (and a bit of oil rad top up, if necessary upstairs) all day, after getting batteries to store cheap rate. Then GCH boiler was removed.

I mention all this just to show how the options can add up, and the ways they can cross-support each other.

Our leccy consumption is now around 10,500kWh pa, but we are fully electric, and includes two BEV's. And of course we have PV that helps a lot. We buy approx 7,500kWh of leccy from Octopus, only 2% or 3% are day rate (unlike your ~50%), and our annual bill is low at ~£600 due to it being mostly cheap 7p rate (now 5.2p). As a bonus, the excess PV we sell back is around £500pa.

So regarding an A2A unit, the million dollar question is do you have a location where it could sit and spread heat through more of the house, by keeping doors open? The shape of your house* suggests you would need one front and back, spreading heat through the ground floor, then naturally 'leaking' upstairs.

Of course, it may make better sense to go for a full ASHP system for the property, using the radiators. Hence why I wondered if you like the idea of aircon, as that would allow you to try the heat side of an A2A almost as a side benefit.

Sorry, too rambly, just ask whatever you need to know, as I suspect I've created more questions than answers, with this post.

*Looking again at your property, and you mentioned extending / two roofs, I'm now thinking that that front roof is smaller than I'd first thought height (depth) wise? But it still looks nice and wide, so perhaps some measurements would be useful, to know if you can get a good to big system, or a really big system, as that will impact all the other future possibilities, such as A2A.

samkellylou

https://forums.moneysavingexpert.com/discussion/comment/81956349#Comment_81956349

Hi Martyn1981

My night rate is currently 9.582p. I try to only use the UFH for a short periods 6am -7.30am, 11.30am-12.30pm and again between 5.30pm -8pm and only to 18 degrees. it is switched off between May and Sept. unfortunately where we live we are reliant on oil as there is no gas line near us. UFH was fitted back in 2010.

your not patronising at all, very informative, never even realised they could heat a home yet 15+ years ago I worked in a portable mobile which I'd imagine used similar technology as it heated through the air con machines.

Hubby would love zircon in the summer and so would my daughter as we use fans in each room to keep us all cool.

Location my initial thoughts would be somewhere like the unheated hallway ( it has wallrock KV600 thermal liner and wallrock fibre liner on the walls to try and keep as much heat as possible) which links the dining room, kitchen and living room together. ( living room is often much colder although it has a central heating radiator but two large French windows which leak energy!

Not sure we can quiet stretch to full ASHP and whether I could live with the retro fit.

I'll try and get the roof measurements too

Thanks again.