It’s not the watt output that matters, it’s how many amps. It it’s a 30 amp output and your heat pump has a starting amp draw of 45 amps it will never start the heat pump.
I could be wrong but I’d be willing to bet that’s your issue.
Get a room air unit and have that for a backup. Thats what we did.
We do have a transfer switch - had the electrician put one in. I have told dad to go get a portable AC unit & he did look at them yesterday. He is a couple months short of 90 & you can’t tell him anything, if you know what I mean :-) He has an engineering degree and I think it’s more the challenge of figuring this thing out .... definitely keeping him out of trouble (inside, out of the heat, away from the chainsaw, etc.)! Thanks for your help/suggestions.
Danny Costanzo: [driving their car on the L tracks] Try not to scrape the third rail, OK? There's about 600 volts in there.
Ray Hughes: It's not the voltage that gets you. It's the amps.
Nun: How many amps are there?
Ray: Enough to push a train. And shut up!
Still my favorite buddy cop show.