Please help us choose which solar & battery set up to go with

HorseWhisperer

We've had four solar installers come and quote for us over the past two weeks and we'd love to get your help in choosing which to go with as they all have their merits.

All installers come with at least three recommendations each from local people who have had solar installed in the past 5 years and who rated them as excellent for workmanship and after-installation service. All are MSC/RECC/NICEIC certified and take credit card payment for deposit.

For background:

Home consumption = 6,123KwH / year

16.6KwH average daily - this does not change much throughout the year as we have lots of old freezers and fridges running and electric fencing (we are a small farm)

Highest daily use was 19.42KwH at Christmas and 19KwH in August (as fridges and freezers are working harder)

Base load = 0.3kwh nighttime, 0.5kwh daytime

We are in the house nearly all day, everyday.

We want solar panels to produce electricity for consumption in this order:

1. Power home
2. Charge battery
3. Sell back to grid

Hot water will be heated overnight on cheap rate Octopus tariff (or from battery/solar if the cheap tariffs disappear in future).

We are toying with the idea of getting a heat pump in the future, so the system needs to be easily expandable.

Available roof space on detached garage:

10m x 3.9m = 40sqm minus approx 1msq for small hips at either end

Aspect - SW with two panels worth of shading from trees from 3pm to 2/3 of roof shaded by 6pm; NE side unshaded from dawn onwards. We'll be using both sides.

Pitch - 40 degrees

Electricity meter is on the side of the garage with a small consumer unit and a trenched feed into the house to the main consumer unit.

All quotes include DNO G99 application, scaffolding, bird proofing & IWA insurance backed workmanship warranties. All quotes based on site visits.

Option 1

22 x Trina Solar 450W Vertex S+ panels

22 x Enphase IQ8HC microinverters incl gateway

Solar system price = £10,985

1 x Fox ESS AC1 G2 5kW AC-coupled inverter

1 x Fox ESS EP11-H 10.36kW battery

Battery price = £4,435

Total = £15,420

Pros: They've been in the business for 14 years; Excellent service so far & thorough investigations into our needs, providing 6 different quotes! Narrow depth of kit so can be wall mounted outside.

Cons = Expensive! We would prefer x2 5kw batteries as easier to expand gradually as another 10kW battery is a big jump and £££; we don't need microinverters on the NE side as unshaded.

Option 1A (same installer as above) 

22 x Trina Solar 450W Vertex S+ panels

22 x Tigo Retrofit Frame Mounted Optimiser TS4-A-O

1 x Fox ESS KH 10kW 1ph Hybrid inverter, 10-year warranty

Solar system price = £9,765

1 x Fox ESS EQ4800-M 4.66kWh Li-ion - Master

1 x Fox ESS EQ4800-S 4.66kWh Li-ion – Slave

Battery price = £4,035

Total = £13,800

Pros: will set it up as three or four strings to maximise power input; quick & easy to more batteries up to ~40kWh; installer came out to do the site visit.

Cons: we will probably want to increase battery size to x2 EQ600 Plus 5.99kWh which will increase the price; this stackable system takes up a lot of space depth-wise (though we do have room); will need to go inside garage due to size; don't need optimisers on both sides as only one side is shaded.

Option 2

22 x 450W All Black Astro N7’s Panels = 9.9kWarray

12 x TIGO Panel Optimisers

1 x Solax IES 8kW Hybrid Inverter

Solar system price = £8,500

2 x Solax IES 5.1kW Batteries

Battery price = £3,800

Total price = £12,300

Pros: Cheapest quote; nice looking kit which will sit on our side garage wall; quick & easy add to more batteries up to ~20kWh

Cons: Company has only been installing solar for 2 years, though the directors are a builder and an electrician who have been trading for a decade or more; their operations manager came out to do the site visit and quote - neither an electrician or installer, though she was very knowledgeable.

Option 3

24 × 450W JA Solar DeepBlue 4.0 Pro = 10.8kW array

24 × Enphase IQ8AC-72-M-INT microinverters

1 × Solis S6-GR1P3.6K-S 3600W inverter

Solar system price = £14,161

1 x Victron Multiplus-II 48/5000/70-50 inverter

2 x Pylontec US500 4.8kWh batteries

Battery price = £4,607

Total price = £18,768

Pros: Company has been installing solar since it was a "thing" 25 years ago; exceptionally knowledgeable managing director came to do site visit - what he doesn't know about electricity isn't worth knowing & blew our brains a bit with all the technical explanations; he lives over the road from us so he will do what it takes to keep his reputation; very high quality kit.

Cons: Very expensive! Very reluctant to move from their techy position - didn't think it was worth putting panels on the NE side of the roof and we had to push for them to quote for that; won't waver on cheaper alternative kit at all - they only fit the best in their opinion; kit can only go inside garage; adding more batteries will be much more expensive than the other systems; we don't need microinverters on the NE side as unshaded.

Option 4

21 × Trina Solar 445W Vertex S+ panels = 9.345kW array

13 x Tigo Retrofit Frame Mounted Optimiser TS4-A-O

SolaX Power X1-IES-8K (8kW)

Solar system price = £10,336

2x SolaX Power TP-HS50E (5.1kWh / 4.6kWh usable) battery

Battery price = £4,641

Total = £14,977

Pros: Been in the solar business 15 years and as electricians for 60+ years (family owned); a qualified electrician did a very thorough site survey and the quote - they don't have "sales" people as such.

Cons: Expensive compared to exact same system as others have quoted for; they seems to be very busy and took 2 weeks to come back with a quote and then was saying they are doing some big factory installations - too busy to come back and rectify quickly if we get problems?

Any thoughts on which of these you think would work for us best, and why, are welcome!

Screwdriva

A few observations and open questions, which I hope will help clarify things for you:

1) Sorry to share, none of the quotes are impressive either from a price or quality of kit standpoint. I'm not sure where you are located but I suspect you may need to cast a slightly wider installer net. 

As an example, Trina Solar is notoriously unreliable and unethical panel manufacturer. JA isn't much better. 

2) Your consumption of 6000+ kWh per annum justifies a battery. But none of the batteries you have been quoted are eligible for the Intelligent Flux tariff, which can be very lucrative for larger installations like yours. 

3) It's hard to tell without images but the shading doesn't sound severe enough to warrant optimizers? Worth considering if it would be easier to trim a few branches instead?

4) No mention of the workmanship warranty for any quote? Not a good sign especially with Chinese kit installed. 

For perspective, installers I use to help other MSE members offer:

24 X Eurener 500W bifacial panels paired to the Tesla PW3 (13.5 kW) for ~£13.5K installed with G99, bird netting and 10 year workmanship warranty.

The Powerwall 3 is eligible for IOF and vastly outperforms all batteries you have been quoted. That's 10% more panel generation, far superior panels and a 30% larger battery than all quotes shared, for less £. 

Hope this helps! 

QrizB

The Enphase microinverter are undersized for your panels and will clip in full sun. So in Quote 3, for example, the IQ8AC-72-M-INT is only rated at 360 watts so your 10.8kWp array is limited to 8.64kW by the inverters.

Screwdriva's comments on the suggested kit are valid too. I wouldn't fit 450 watt panels when 500 watt ones will fit; the labour, mounting and wiring cost for fitting each panel is the same for both, and dwarf the cost of the panels themselves. It might cost £250 to put a panel on the roof, of which £100 or less is the cost of the panel. (The limitations of the Enphase microinverters might be why your installers are favouring lower-output panels, as you won't benefit from anything larger?)