General question about Inverter rated capacity

[James.huang10]

Hi all,

I tried doing my own research first and all leads says that the inverter output can never be more than the rated capacity. If i have a H1 G2 5kw inverter, how come I am seeing 1.8 kw charging my battery and 3.6kw load into the house which is about 5.4kw in total?

I just got a system installed recently and trying to learn more about how a solar system actually works. Sorry if this is a noobie question

[Dave Foster]

The inverter can never output more than it's rated AC capacity so your H1 5.0 can output a maximum of 5kW on the AC side (i.e. your house load and grid), but the batteries are on the DC side of the bus and if your array is over capacity (say at 6kWp) you would be able to output 5kW AC and charge your batteries at 1kW.

Many systems are slightly over-rated on the PV array, you can't exceed the inverter string power/current limits but often the array will be 115% maximum inverter AC output.
Also that rating is at 25C, the array derates above that but increase below that and so on a perfect sunny day when the ambient temperature is low you can see higher output on your array, the trick is to make sure your batteries have some space in them to accept the excess otherwise the array will derate and you will see clipping.

[James.huang10]

The inverter can never output more than it's rated AC capacity so your H1 5.0 can output a maximum of 5kW on the AC side (i.e. your house load and grid), but the batteries are on the DC side of the bus and if your array is over capacity (say at 6kWp) you would be able to output 5kW AC and charge your batteries at 1kW.

Many systems are slightly over-rated on the PV array, you can't exceed the inverter string power/current limits but often the array will be 115% maximum inverter AC output.
Also that rating is at 25C, the array derates above that but increase below that and so on a perfect sunny day when the ambient temperature is low you can see higher output on your array, the trick is to make sure your batteries have some space in them to accept the excess otherwise the array will derate and you will see clipping.

Thanks so much for the explanation! Looks like my limited knowledge of AC vs DC is what confused me. I have some followup questions if that's okay. Is the Solar going into the house load and BESS going into the house load separate or related? Example for my 5kw inverter, if i have a EV charging at 7kw and my solar PV is generating 5kw, the 5kw will go towards the load and will the remaining 2kw needed for the load come from the BESS or from grid import?

Thirdly, is there a setting to limit the inverter AC output? Reason i ask is at my parents place, they requested for a 5kw inverter and all documentation says its 5kw, but they actually got a 6kw one instead (H1-6.0-E-G2), the installers didnt tell us we got a free upgrade so i assume it was due to 5kw being out of stock and just gave us a 6kw, but i want to see whether (if there's a setting) on whether the installers throttled the output to be 5kw or left it at 6kw, if that makes sense?

Much appreciated for your assistance.

[Dave Foster]

Is the Solar going into the house load and BESS going into the house load separate or related? Example for my 5kw inverter, if i have a EV charging at 7kw and my solar PV is generating 5kw, the 5kw will go towards the load and will the remaining 2kw needed for the load come from the BESS or from grid import?

The inverter mixes solar and battery on it’s internal DC bus before it is converted to AC for grid connection.

For any load the inverters CT clamp can see (i.e. sometimes the EV is connected up stream and won’t be seen by the inverter), the inverter will try to meet that load (to it’s 5kW limit) from solar if there is enough otherwise the difference will be drawn from the battery, any difference will then be made up from the grid.

Thirdly, is there a setting to limit the inverter AC output? Reason i ask is at my parents place, they requested for a 5kw inverter and all documentation says its 5kw, but they actually got a 6kw one instead (H1-6.0-E-G2), the installers didnt tell us we got a free upgrade so i assume it was due to 5kw being out of stock and just gave us a 6kw, but i want to see whether (if there's a setting) on whether the installers throttled the output to be 5kw or left it at 6kw, if that makes sense?

Much appreciated for your assistance.

It’s surprisingly common for that to happen, main thing will be the G99 if it says 5kW then you should consider reducing the export power to 5kW (but the inverter will still be able to meet 6kW house loads), however if the G99 says 6kW best to leave it as it is.

It depends what you want to limit, the inverter can be throttled by either it’s export control (which controls how much it is allowed to export after any house load is removed), or it can be throttled to a % of it’s total power output which will control everything it does so if you were to set that to 84% it would only be able to output a fraction over 5kW.
Both of those settings can be found by going into the inverter settings at the panel Settings (password=0,0,0,0), on-grid, Export Control (set to 5000 watts or return to 60000 watts for its default not set).
Power Limit is in the same on-grid menu and sets the % of the maximum inverter size you want it to limit to - thus controlling both max export and load capability.