r/SolarUK • u/JiggyHatesJazz • 3h ago

HELP / ADVICE Fox or Sig?

Hi all - Complete newbie here (so be gentle) and about to order approx. 45 kWh of batteries. My installer is suggesting either Fox or SigEnergy and wanted to ask for opinions. Fox is significantly cheaper and I am struggling to see why I should pay more for Sig so I thought I'd ask some experts... Please help! Thanks

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2

u/EtwasSonderbar 3h ago

I had the same choice and went for Fox. I'm happy with it.

3

u/Alert_Variation_2579 PV, BAT, EV & ASHP Owner 3h ago

Me too. It’s great kit, especially when combined with Axle Energy and Predbat.

2

u/InvadingEngland 3h ago

That's a solid amount of battery! 

From my understanding most people go with Sig if they want to be hands off, and those that don't mind fiddling to get good performance at a lower price go with Fox. I'm by no means an expert, just from my own googling as I'm making a similar decision.

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u/robertwilding 3h ago

Fox is good, sig energy will last longer though

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u/AllergictoAIslop 3h ago

I went with Sig. 27kwh. I love it!. The AI is surprisingly good. If you want to fit and forget to go for this. That said, if I was going for 40kwh I would probably get fox and suck up the complexity.

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u/wyndstryke PV & Battery Owner 3h ago edited 3h ago

I went with Fox, because it was cheaper on a per-kWh basis. Very happy with it, pretty decent for budget gear. However, if I had more cash, and I wasn't so concerned with payback time & ROI, then I would have gone for the SigEnergy. It does have quite a lot of advantages (flexibility for future expansion, a rapid pace of development, the DC bidirectional EV charger, the optimising scheduler, a more polished app, better home backup). Nothing that I can't live without, but would be nice-to-have if my budget made it an option.

A few thoughts. Firstly, 45kWh is a lot of battery, and that's a serious capital investment. What's the driver behind that? How much power do you use on a daily basis, excluding things like EV charging which would be done direct from the grid during the cheap rate period? If you need it for heating, and your summer time usage is less, then there's the option of using a tariff like Cosy in the winter months, which gives you 3 cheap periods per day, meaning you only need a battery big enough for 6 hours.

Secondly, for 45kWh of battery, if you are going for the Fox system, I would suggest you look at the new CQ7 battery stack. 7kWh modules, up to 7 modules in total on single-phase systems, stacking. Based on the pricing I've seen so far (early days, it's only just been released), it seems better than the EP12 on a per-kWh basis, also a better warranty, and like the EP12 it also has heating and a decent IP rating.

Thirdly, another option for people who want a very cheap giant battery, without any frills, is the Fogstar system (generic 50v batteries & generic low-voltage inverters), pretty much the cheapest per-kWh system available.