New solar install advice for very power hungry household!

sunpower65

Hi,

Wondered if I could tap the expertise here, assuming i'm on the correct board! I'm looking to get some solar installed, at the house we moved to a year ago but its getting quite complex and expensive. Over the last year we have used around 16,000 KWH per year, mainly in spring and summer as unfortunately the house comes with a pool with air source heat pump and an electric hot tub. Usage in winter is considerably lower.

We have two phase power currently but am told by the electricity people they can upgrade to 3 phase for maximum £2k could be less. Understand this could reduce the cost of the solar as the quotes now both include two solar inverters for each phase one has the pool etc on and one for the house.

The house faces south west, with the proposal to put the panels on the garage and outbuildings, they face south east as shown below. the second proposal puts them on the south east side and also and on the other south east section in red. They wont go on the south west sections, no space trust me and we might have to trim a tree. There is quite a bit of shading over the day across the roofs, but told its doable.

Currently we don't have a smart meter but will get one.

I'm after a reliable equipment provider that will be around in ten years time if things go wrong so a little nervous of Sigenergy just because they are quite new?

Any thoughts very gratefully received.

Thanks!

Quote 1

32 x SunPower P7 455W N-type Topcon solar panels
GSE Integrated In-roof mounting system
2 x SolarEdge 6kW solar inverter
32 x SolarEdge S500 power optimisers
2 x Tesla Powerwall 3 battery storage 13.5 kWh (Including 1 x Gateway)
All DC and AC isolators, cabling, trunking, etc.
ins labour , scaffold, 1 story and 5 year workmanship.
Solar £19,729
Battery £14,129
Total £33,858

Quote 2
system 10.58KWp + 10.12KWp
2 EM-LITE Bi Directional generation meter
2 sigenergy power sensor
2 sigenergy 6kw hybrid inverter
2 sigenergy 10 Battery 9KW
1 sigenergy gateway backup
45 jinko soalr 460W
45 TIGO energy optimisers
total £25,801

Qyburn

Can't you connect the panels right into the PW3s, removing the need for Solaredge inverters and optimisers?

Screwdriva

https://forums.moneysavingexpert.com/discussion/6658890/new-solar-install-advice-for-very-power-hungry-household

Hi there! Thought I'd share a few thoughts, which I hope provide perspective and prove useful:

1) Your intuition to doubt Sigenergy is spot on! I would veer clear of any Solar brand lacking a track record of several years, especially ones with poor reputations. Junko panels included.

2) You do not need one inverter per phase unless whole house backup is desired for the pool as well? It may be more pragmatic to proceed with 1 PW3 + 1 expansion pack for the household? (But that's just me thinking the last thing I would want to do is jump in the pool during a blackout)

3) I would delete the NNW aspect facing panels (as shown on the diagram) as these will generate < 50% of their South facing counterparts per year. I would cover every inch of the South East and South West aspects you mention.

4) Did you have an in person survey completed? Did you insist on in-roof panels or did the installer suggest this?

5) Re: shading, an image of the roof to highlight how bad the shading is could be useful. If it is severe, SolarEdge may be the path forward with a AC coupled PW3. But this is only recommended when shade covers a substantial portion of the panel.

Here is quote from an installer I use (to help others) that is comparable:

28 x 515w Eurener Bi-Facial Panels - 30-year warranty
1 x Tesla Powerwall 3 13.5kW battery inverter 10-year unit replacement warranty

1 x Tesla Gateway 2 10-year warranty
1 x Bird Protection
1 x 10 year workmanship warranty (twice the duration).

£14K installed, on roof, all inclusive. If more panels can fit on the South aspects, add £200 per panel.

If additional storage is required, you can always add a Tesla expansion pack for an additional ~£4K and capitalize on the £750 rebate (as long as you place the order before 31/3).

Hope this helps!

Martyn1981

https://forums.moneysavingexpert.com/discussion/comment/81916468#Comment_81916468

My immediate thought too, but the OP does mention a lot of shading.

How are panels doing these days with lots of bypasses, might that help enough with the shading to go directly to the PW3's as you suggest.

Wonder if there are now panels, like the new Tesla panels just launched with 18 power zones (up from 6)?

Martyn1981

Just a thought on the 3phase. £2k is pretty cheap, presumably because the connection is easy, no need for major works, so a nice bit of future proofing, for a reasonable price.

Could allow you to charge an EV at upto 22kW, if you ever want though (though most cap out at around 12kW atm). Also, Tesla has just launched their 3phase PW3 the 3P. But still early days.

Also, probably need a smart meter. I know that my sister's smart meter nets the export and import on the 3 phases, so even if they pull power on one phase, exceeding the PV generation split across that phase of the 3 phases, then they still don't get charged for import, if the total generation exceeds total import. [Might be the same for non-smart meters, I'm not sure?]

Although, balancing phases less important, if you have a battery doing that for you.

sunpower65

Awesome thanks so much everyone all really helpful!

A couple of follow ups - any idea when the Powerwall 3 THREE phase might be available in the UK?

Can you recommend any other good 3 phase solutions as sounds like this might be a good option, I think Solar Edge do one?

The shading is from some tall narrow trees over the day so intermittent but covers maybe 1.5 to 2m of roof as it passes.

Thanks again!

Screwdriva

https://forums.moneysavingexpert.com/discussion/comment/81917885#Comment_81917885

I've spoken with Tesla about the 3P. The informal and unofficial answers I received was "3-6 months". And it "will be priced higher".

Out of curiosity, do you really need a 3 phase set up? Or are you tempted because the price to add a phase seems reasonable?

I ask because a single PW3 + expansion pack can easily power the entire household while saving you a small fortune (see quote shared above). And with what sounds like minor shading, SolarEdge would be overkill.

I've attached an image of a large property I have helped below. 10kW SolarEdge + Tesla PW3 (homeowner wanted maximum panel coverage on all 3 aspects) . Note the extreme tree shading to the left. This is what I would describe as shading that warrants optimizers. For minor shading, the 3 bypass diodes contained within each panel + the 3 strings for the PW3 + good layout design, should be more than enough to compensate.

Hope this helps put things into perspective?

NedS

https://forums.moneysavingexpert.com/discussion/comment/81917944#Comment_81917944

Nice to see the architect gave reasonable consideration to roof design for a property where maximum solar coverage was a priority. I cannot imagine a worse roof design if I tried.

Screwdriva

https://forums.moneysavingexpert.com/discussion/comment/81917982#Comment_81917982

It was, by far, the most complex roof I've been involved with. But the end result, especially when viewed at ground level, is very pleasing.

Then there's the owner's insistence on a heat pump which has meant the involvement of an elite Heat Geek installer and a 5kW ASHP to heat the entire property :)

Qyburn

https://forums.moneysavingexpert.com/discussion/comment/81917944#Comment_81917944

How does the PW3 handle a two phase supply?

NedS

https://forums.moneysavingexpert.com/discussion/comment/81918179#Comment_81918179

A single phase PW3 can be installed on each phase. Just view it like two individual supplies to the property that happen to be out of phase, with net metering (i.e, export on one phase within a 30min period would offset import on the other phase to create overall billable usage or export for the 30min period).