I bought a really nice Cal Spa 10 seater about four years ago at a show. Great spa, but boy does it cost a lot of money to run...
We ended up shutting it off to see what the bill did. Went from $380/month to $230. No question about why either. $350+ for 18 months, $250 and under since. During summer... with two air conditioners. Looks like it costs less to run air condition than it does to own a spa.
We may get rid of it...
Thats why I by-passd the electric and plumbed in a gas heater. 250 btu small pool sized that goes from idle to temp in 45- 60 minutes. But I only use it a couple of times a month.