It would be good to actually name the brand & model, whether the problem was noticed on one unit or several units and whether there are configuration options which could affect behaviour. Also, what does the supplier / dealer say about it?
Yeah. It's Deye which I was initially uncertain to disclose because I have no basis to say they would be the only ones who do this poorly. Others we have tested seem to do better but not
that much better, around 40W low-load consumption seems to be industry norm. Which is why I wanted to open this as more generic discussion because starting from 2025 EU is going to regulate stuff like energy meters and routers (usually 1/home) to nearly ridiculously low consumption requirements which are actually difficult to achieve while other products that are touted to go to every home as part of "green transition" then do 300 times worse.
The technical support of the label company confirmed that 100W idle consumption would be completely normal so that pretty much rules out unit-to-unit problem.
Configuration options I don't know, I have tried going through the menus and tried various tricks over modbus but could not find a lower power idle state and the support did not know about such either, just saying 100W is normal.
A quick Google shows me that it looks like there are settings on some units to make the DC to AC part of inverter go into low power standby mode in case there is no load detected. It looks like the DC to AC part of the inverter is always on which causes the excessive power draw (which seems rather odd to me as well).
The problem is, there almost never is "no load" condition.
There are actually two important aspects, availability of sleep mode you mention but also low quiescent consumption at near-zero power in active state. Latter is also very important, probably more important than the sleep state, because these battery inverters supply house loads often nearly 24/7 and those loads are occasionally like 100-300W. Well, from optimization viewpoint maybe we could enter a sleep state (if that was available) and buy that 100-300W from grid instead, but then what if consumption is 500W and electricity expensive, then we surely want to supply from battery and it makes a huge difference if the efficiency is 70% vs. 90% at that power level, so low-load loss matters.
Sure, at 1/100 of rated power just enter sleep mode, but one of the primary purposes is to store solar and self-consume during the evening, night and morning hours, so during 10-20 hours or at C/10 - C/20.
If I was dictator of EU I would write the requirements for certain peak efficiency at rated power but then also efficiency at say 1/20 of rated power and finally self-consumption at zero battery power, so that the inverter is allowed to enter some kind of sleep mode. Like, 97%, 90% and 5W respectively should be possible to engineer. But lacking regulation, manufacturers have no motivation to think about energy efficiency.
100W continuous extra draw is is 900kWh a year or say 13MWh over the lifetime of the inverter. This extra electricity costs more than the inverter itself!
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