While the PV was charging the battery bank this morning, I turned on the MSW inverter, and tested it on a few things in the basement.
1. 1/3 HP Ace sump pump (short test, no water)
2. Large Craftsman power drill (360w)
3. Ceramic space heat (at 952w)
4. Small basement freezer (180w intermittently for 3 hours)
I had a 100watt flood lamp plugged in while I was running these tests,
and didn't see any dimming at all.
The solar charge controller did it's work earlier this morning and has been in 'Float' mode.
All the juice for the testing is extra PV power that wasn't being used..
(So, I didn't waste any power)..
It looks like the inverter uses very little power in standby mode. (Without loads).
I think it's less than 5W. Will have to use a real amp meter to tell for sure.