"For my kitchen refrigerator, I can only find the Energy Star label, but not any other documentation of peak/average wattage. Is there a good way to test this? I've looked at the Kill A Watt (
https://www.amazon.com/P3-P4400-Electri ... rg-20&th=1 ), but it seems this will only tell me the current wattage of the appliance, and not the peak wattage. Is this correct? My understanding is that refrigerators/freezers don't use a lot of energy normally, but will use it when the compressor turns on (is this just standing there waiting for it to make noise, and then looking at the display to see if this is the "peak" value?)"
FWIW: I happen to have our newish freezer plugged into a Kill-a-watt, set to display watts. It was displaying 0.3 watts. I opened the door, and the wattage jumped to 3 watts (that's the light). I turned the dial to the coldest setting while watching the meter ... when the compressor came on the wattage jumped to 155 for a couple of seconds, then went to 90 some for the rest of the cycle. The actual peak wattage was probably slightly higher, because the kill-a-watt only updates the display every half second or so, but then inverters have a surge capacity, too)
(this freezer has a energy label of 461 kwh/yr. It uses less than that, perhaps because it's in a fairly cool basement)
"Our last power outage lasted 2 days, but power turned on for a few hours in the middle of the night. For such a situation, would we need a combo charger-inverter to be able to re-charge during this time?"
The inverter chargers I'm familiar with are hundreds of dollars.
I don't see why you couldn't have the charger plugged in and connected to the battery, and also have the inverter connected; if the power comes on, then the charger would start charging.
One caveat, though ... most automotive type battery chargers don't push a lot of current. For example, the freezer above uses about 750 wh/day, or
roughly 30 watts if it ran continuously. A 10 amp charger is pushing 10*12=120 watts (although there are some inefficiencies, so the practical value will be less). So 1 hour of charging will run the freezer for 3.something hours - it's not like the power coming on for a brief interval will charge a beefy battery back to full in a couple of hours.
Also, specifically related to the 30 amp charger mentioned upthread, I thought 'that's pretty cheap for a 30 amp charger', but the manual is a little confusing. The 30 amp rate is in 'boost mode' From my reading of the manual, it wasn't clear if it would do that indefinitely; the 'charge' current was 10 or 12 amps. And apropos the power coming on in the middle of the night, it sounded like you had to manually select the 'boost' mode; by default you got the lower current.
There are chargers intended for using generators to charge off grid battery banks that will push high currents - 30 to 100 amps. 'Iota' is one brand. But they aren't all that cheap. Here is one for $130:
https://www.solar-electric.com/iota-eng ... ls-30.html
(not a recommendation, just an example)