Brave performance

My system consists of 2 Synergji/Axpert MKS5K 5kW off grid inverters in parallel, total 10kW. I have a total of 400Ah LFP battery and some 4kW solar panels.
Lately the municipality changed tariffs and introduced a base charge depending on the max power allowance. In order to save money I had it reduced from default 60A to 45A. That amounts to 10.35kW. This function is built into the prepaid meter.
One day at dinner cooking time the cooks managed to draw close to 6kW while accidentally the geyser ran with 3kW. The system normally runs off grid and the batteries were well charged. However the heavy load of close to 9kW pulled the battery voltage down, the kettle effect, below 47V where my setting for "back to grid" is. So the inverters switched to grid bypass mode. So far so good, however then the battery chargers kicked in with 2kW. The total charge was then close to 11kW, off limit for the meter that tripped. With the grid power cut off the inverters acted like an UPS and switched again to battery mode. After a while the meter automatically resumed power delivery. The inverters recognized the presence of grid power and with battery voltage below 47V switched back to grid bypass mode. The game started over a couple of times until I turned off the geyser.
Conclusion is that the inverter system has well performed, there was no blackout in the house. And we have to watch the geyser being turned off during cooking.

46 minutes ago, Beat said:

Brave performance

My system consists of 2 Synergji/Axpert MKS5K 5kW off grid inverters in parallel, total 10kW. I have a total of 400Ah LFP battery and some 4kW solar panels.
Lately the municipality changed tariffs and introduced a base charge depending on the max power allowance. In order to save money I had it reduced from default 60A to 45A. That amounts to 10.35kW. This function is built into the prepaid meter.
One day at dinner cooking time the cooks managed to draw close to 6kW while accidentally the geyser ran with 3kW. The system normally runs off grid and the batteries were well charged. However the heavy load of close to 9kW pulled the battery voltage down, the kettle effect, below 47V where my setting for "back to grid" is. So the inverters switched to grid bypass mode. So far so good, however then the battery chargers kicked in with 2kW. The total charge was then close to 11kW, off limit for the meter that tripped. With the grid power cut off the inverters acted like an UPS and switched again to battery mode. After a while the meter automatically resumed power delivery. The inverters recognized the presence of grid power and with battery voltage below 47V switched back to grid bypass mode. The game started over a couple of times until I turned off the geyser.
Conclusion is that the inverter system has well performed, there was no blackout in the house. And we have to watch the geyser being turned off during cooking.

There have been a few posts lately about folks with relatively large inverters relative to a somewhat limited grid supply. Sorry to hijack, this doesn't help your specific case now, but the Sunsynk/Deye hybrid inverters have a peak-shaving function that is supposed to specifically support weaker (/cheaper) grid supplies, limit the draw from the grid, and seamlessly blend in battery power to meet the load. That could be a somewhat elegant solution for those who want to cut costs as above, but not suffer too much disruption.