Koolau
Give me a museum and I'll fill it. (Picasso) Give me a forum ...
I don't think a heat pump costs a lot more than an AC, and you do need an AC in Hawaii.
It's true we have a lot of ACs in Hawaii. Anything close to sea level and NOT oriented to the Trade Winds, probably has to have AC. Office buildings, hotels and Ewa homes all have AC. IF you have AC, it's unlikely you will ever really need heat. BUT, if you NEED heat, then you almost never need AC because you only need heat if you are above about 2000 feet (usually more). At that altitude you only need heat - not AC, SO a heat pump loses a fair amount of its appeal as a dual purpose, relatively expensive installation.
You can pick up a 5000 watt resistance heater at a garage sale for $10 (when someone moves.) That will heat your bathroom or bedroom at night. In the day time, you can use your wood stove/fire place. Such sets ups almost never even have a room AC unit as it never gets hot. Vice Versa, IF you have AC, you can usually get by with a window unit for night (for sleeping) and you'll never need heat. "Expensive" set-ups are the split units that allow you to pick in which room you actually use the AC that's being generated. Again, if you have this set up, you never need heat. It's kind of a unique situation in the USA. I don't even recall a TV add offering a heat pump, though I suppose they do exist in the Islands - just never heard of it.
We're in the zone of NO heat and NO AC. Our condo is oriented so the Trades blow in one side and exit the other. We're sort of "open air." A few days every year when the Trades die, it would be nice to have AC, but the building forbids window units. I know one couple who uses one of those portable ACs that the ambient air/heat exhaust is coaxial and just sticks out a window. Since they make virtually no noise, no one cares. We just kick off the covers at night if it ever gets hot/muggy. Once in a while (2 or 3 times/year) I'll warm up the shower with the blow dryer in "winter." Other than that, we have no heat. YMMV