question

Search for “victron efficiency curve” and have a look at the white paper that comes up. Those curves are for the big models, but the little ones will probably have a similar characteristic shape.

The very tiny, continuous load might be best served by its own dedicated, very small inverter, if every watt-hour counts. Those units have a baseline demand of only ~4W in continuous operation.

https://www.photovoltaikforum.com/thread/133886-effizienzkurven-wechselrichter-victron-oder-fahre-ich-mit-2-wechselrichtern-wirk/

Phoenix 24 375 vs Multi 24 3000

Look at the second picture on the first page, the first time I made a booboo.

Note, how bad the 375 gets when loaded towards its rated power but how good it is below 170ish watts. You gotta calculate the actual time it is in either state and can only then decide which way to go...

Any updates on efficiency curves for individual models? I just bought a Victron Phoenix 24/500, which I choose assuming it will have good efficiencies in the 50-200W range, but I've measured it and it's nowhere near specs. Idle current is 0.4A (~11W) and measured efficiency at various points is 83-85% with a maximum of little below 87% at 170W output. Don't see anywhere the 90% indicated efficiency in specs... While model looks solid, if multiplus efficiencies are real, then it's actually way more efficient than what I have for almost all ranges, which is counterintuitive.

Would also be nice to see efficiency curves at various power factors also. And maybe a way on the app to see the actual efficiency of the inverter for last x kWh used from battery.

you always will have an dc current overhead for the control board and relays on it, the more features a unit has, the more power it consumes.

Are you saying that the 4W difference in idle from specs to real usage is the control board? If yes, this is honestly deceiving and should be included in the specs.