Hybrid grid-tie inverter with small standby consumption (5...8 kWp)

[rilonau]

Hi all,

we are planning on a new PV-installation on our south-east roof, estimating 6...10 kWp of solar power. We also plan a diy battery (LFP 16 cells, 280 Ah, 48V) and look for a decent hybrid inverter with very low stand-by consumption (night use). We live in Germany in an own house, so we have 3 phases on 400 V (between phases in Germany). With a 1-phase inverter you can roughly output max. 5 kW, of course a 3phase inverter would be more suitable. But i read that most 3phase inverters have quite a high stand-by consumption of 100 - 150 W. This is way too much imho, esp. for night-use where you only need little electricity for the fridge or the water pump or the oil heater (100...200 W, avg. 50...80 W). The 1phase inverters run on much less stand-by consumption (from 20...50 W).
I don't want to use the battery for up to 1.5 or even 2 kWh just for stand-by and little bit of house electricity needed. The inverter could switch off completely during night or go into 'deep sleep' when battery gets below say 50% SoC.

What inverter would you recommend? Should i opt for 1phase or 3phase? What is the best option in term of efficiency and low stand-by consumption?

Thank you!

 

[RCinFLA]

In Germany, homes usually have 400 vac three phase at 63A per phase feeds with 230vac service to neutral. Since you are talking about low power useage I assume the loads you want to power are 230 vac single phase.

Look for a 230vac single phase hybrid inverter that meets your power need and look at its idle power. Hopefully the low power loads you want to power are from same phase, otherwise you will need a second or third inverter for the other phases.

You likely will not find lower idle power than Victron inverters. Three Victron inverters can be setup to run three phase. Each 230vac inverter will be connected to neutral and one hot phase and will supply 400vac between two inverter hot line outputs and 230vac between hot and neutral.

 

[rilonau]

Yes, thanks. Most consumers are single phase (230 VAC), only the oven in the kitchen uses all 3 phases (and can be run on grid only). What is the idle power of the victron inverters?
If i only use 1 phase, power is limited to 230V x 16Amps (below 5 kW). If we get a 8 kWp PV installed in 80+% of the time the output will be lower than 5 kW i guess. In 20% of the time we might get 6 ...7 kW - so we will lose the additional power. With a 3phase inverter i will have high permanent losses, when it runs 24/7. I could only imagine to shut down the inverter at night time or switch to a small and efficient single phase inverter powered by the battery. The switching should be done automaticly, when PV output is lower than a threshold, say 200 W. Would this be a good solution? Are there inverters which can do all that in one? Check the PV input and switch to single phase mode or deep sleep if there is no consumption?