FoxESS Community - Owners & Installers Forum

Hello,

A simple question really. One that has sparked a few arguments!

On the KH 10.5 kWh Foxess Inverter - when the grid is available, and the house is running off the grid (i.e. the Inverter is not drawing from the batteries and the batteries are at 100%), how much can I draw from the grid? Am I limited to sticking under the 10.5 kWh or can it go over this?

The amount your grid can supply will be limited by your grid feed, the inverter works with the grid to reduce the amount the grid has to deliver, and the KH will support up to 10.5kwh as long as you have enough solar/and or batteries to provide that power.
Once your feed goes above the maximum limit of the inverter your grid will provide the rest until you hit the grid limit or blow your main fuse.

Great, thank you so much Dave! This is often quite a point of confusion.

I don't know what the 'grid feed limit' is, but the point I'm trying to clarify is whether it is limited to under 10.5 kWh or not. I've had several people have heated arguments with me telling me that I simply cannot draw more than 10.5 kWh at ANY point in time.

However if I'm understanding your explanation correctly, then it is completely fine to go over the Inverter limit of 10.5 kWh provided the grid is available. (For example microwave + stove + a few heaters (certainly nothing above 20 kWh)).

Am I correct? This means that not all the power has to go through the Inverter - which quite frankly is a huge win and cleverly designed. It means I don't need to go around policing the household usage

Yes that's spot on, the inverter is wired in parallel - it 'assists' the grid supply rather than limit it.

When your inverter has enough solar or battery to provide the full 10.5kw, everything up to that will be provided by the inverter, but if you need more it will be supplied from the grid.

The inverter will provide up to it's limit and the grid will provide everything else, in the UK your incoming fuse typically specifies your maximum grid limit - mine is 100A (@230v), and I have a 6kw inverter so in practice 23kw + 6kw is possible (as long as the circuit breakers and wiring can cope with that demand).

Forest124 wrote: ↑Wed Nov 15, 2023 12:02 pm Great, thank you so much Dave! This is often quite a point of confusion.

I don't know what the 'grid feed limit' is, but the point I'm trying to clarify is whether it is limited to under 10.5 kWh or not. I've had several people have heated arguments with me telling me that I simply cannot draw more than 10.5 kWh at ANY point in time.

However if I'm understanding your explanation correctly, then it is completely fine to go over the Inverter limit of 10.5 kWh provided the grid is available. (For example microwave + stove + a few heaters (certainly nothing above 20 kWh)).

Am I correct? This means that not all the power has to go through the Inverter - which quite frankly is a huge win and cleverly designed. It means I don't need to go around policing the household usage

Worth noting that this should be expressed in kilowatts (ie power, how fast you are using energy) rather than kilowatt hours (a measure of how much energy is consumed).

Your grid connection places an upper limit on how many kilowatts you can draw, but there is no physical upper limit* to how many kilowatt hours you can consume.

You can get a rough idea of the grid limit by multiplying your main supply fuse rating in amps, by 230V ie nominal mains voltage. We have a 100A supply giving us a limit of ~23kW, which is not a value we ever really approach. I think the highest I ever saw was around 16kW overnight, when the car was charging (7kW), as was the house battery (~3.5kW) and both the dishwasher and washing machine were heating water at the same time (~2.2kW each). We'd have blown the fuse on the 60 amp supply that many older houses still have, though! (Actually the EV charger would have throttled back, but I digress).

(*Technically, the limit would be the amount of energy you would use if you were pulling the maximum draw through your grid connection 24/7. In practice of course, this doesn't actually happen! )