I live on the big island and pay over $.40/KWH so a $700 bill would be more like $200 on the mainland.

That is one reason why my new house is off grid solar - cheap (compared to $.40/KWH), clean electricity.

The other is that the grid here is unreliable. I had 87 outage events last year for a total of 37 hours and that is not including the nine days with out power post hurricane.

Now don't get me started on internet quality!!!

Many people, at least on O'ahu, live in urban areas with serious "heat island" going on. In those locations, if your windows catch the prevailing winds, you don't need a/c, or perhaps only rarely. If there are buildings or terrain blocking the breeze, however, you'll be more comfortable if you have a/c, or if you make some lifestyle changes that make it less necessary.

That said, when I lived there, my bills never approached that figure, even with a/c.

My bill got up above $500 one month (normally around $350) without A/C. My friend's cousin on Maui had a new neighbor move in next door from the mainland and installed central A/C like every decent apartment on the mainland has. Their first month's electricity bill was $3,000 (three thousand United States dollars) because of that A/C. It gets very expensive, very fast.

It may not be A/C. A pool with a single speed pump plus an in-ground hot tub could conceivably run between four and five hundred bucks a month for heating. Of course if that's the case he could save a couple hundred bucks a month by installing a solar heating system and a two speed pump.

Some microclimates of Hawaii, like up Mauna Kea, get fairly cold. Electric heat can use a lot of power there.

Got to be Bitcoin mining.

Could be a business.