FoxESS Community - Owners & Installers Forum

Hi,

I've been quoted the following and just wanted to check what the company is saying makes sense.

12 x SunPower 450w Panels (7 SE, 5SW)
1 x Fox 5KW Hybrid Inverter
2 x Fox EP11 Batteries

Total install price: £12500.

They have estimated 5282 kWh generation per year.

Does this seem like a reasonable quote?

Now my questions:

- The total of the solar array is 5.4kw, they've quoted a 5kw instead of a 6kw inverter. Any reason for not getting the bigger inverter?

- My house has a max peak usage that I've seen of 6.3kw (Have a hot tub running). With a 5Kw inverter, this is obviously going to cap it and mean I will always need grid power at these peak times. I originally asked for the KH 7kw inverter but was told this wouldn't work with the PV system as the minimum start-up voltage wouldn't be there. Is this actually the case?

- The installer also stated the batteries only have a max output to the house of 6kw. Is this also the case? Couldn't see a max output listed in the spec sheet but have seen people say it's around 9.5kw output. So again, with say a 5 or 6kw inverter am I limiting the output to the house from the batteries and the remainder would then come from grid? Would the 7kw inverter be able to deliver at 7kw from the batteries?

- Are all EP11 batteries being fitted/delivered now the with built-in heater version?

- The installer also stated that there is no home backup with this system. I see that EPS is standard with either the KH or H1 inverter. Do they just mean whole house backup isn't available and that it would need the additional EPS box fitted or are they misleading me?

Hi, the price looks ok - some of it is driven by the amount of scaffold you will need if you have multiple elevations, but it doesn't seem unreasonable.

It is better to slightly over power the inverter as it is unusual on multi elevations for all panels to be producing full power at the same time, even on the clearest days - and 5.4kWp is only a modest amount over so no problem with that.

Buyers remorse tends to involve wishing they had installed more solar panels (or batteries) and so now is a good time to make sure you maximise the number of panels on your roof whilst the scaffold is up.

As you say the inverters max output is 5kW but it can output 5kW and be charging the batteries with the excess if there is more generation available.

The KH7 inverter is excellent and whilst 5 panels is a small number I have not heard of startup problems with that number before - if you have unfavourable conditions, shade or shadows that might be driving the decision, but if all 5 panels are pointing in the same direction with a reasonable elevation I would expect it to work without problem.

There's no reason why you couldn't have the H1-6.0 inverter, you'll not achieve it's full output from solar but you will whilst on batteries - so i'd recommend at a minimum you have the 6kW (it's only a tiny price increase - possibly zero cost).

Onto the batteries, the EP11's are great batteries, they are high voltage with a nominal 384V - output will depend on the inverter rating but an H1 can discharge at 40A and a KH at 50A - the BMS will throttle this if the batteries are cold but generally you should be able to achieve those limits.

The thing to say is whilst you can have a max discharge current of 40A or 50A the recommended discharge is 27A but even at that (if the inverter was rated for it) you could output at over 10kW, but in either case the batteries would support the maximum output of any of the inverters you have mentioned (they will discharge a bit higher ~300w because of losses)

To the best of my knowledge all EP11's are now fitted the heater (there may be a few n on heated still in the supply chains), but the way to deal with that is to specify it as part of the order.

The inverters don't as standard have a home backup solution, you can wire up the EPS circuits to deliver this but it requires additional wiring, a changeover box that disconnects the grid connection should it fail (a legal requirement) and you will likely need an earth rod installing as the house earth will be disconnected in the event of a grid failure. This does cost quite a bit to achieve all of this, some people just say - can you install an extension lead for me to plug into when there is a failure which is simple enough but the best solutions to move towards home backup do require extra costs.

This company make home backup/EPS changeover solutions for the Fox inverters https://www.eco-ess.co.uk/automatic-cha ... r-systems/