Gas appliances don't use much electricity at all, which is why they are popular. We have gas heat, hot water and even a gas clothes dryer. During the blackout of Super Storm Sandy I was able to run my gas heat off my generator and STILL run two fridges. (as it's now October I'm wondering what the end of THIS month will bring: Last year was Sandy, the year before the FrankenBlizzard).

18 hours a day for a 1 hp pump and is an awful lot unless your pool is gigantic. I have a 1hp 2speed and I run it 12 hours a day on low speed (about 1/4 hp I guess) with a 19,000 gallon pool. That's almost certainly the cause of your increased bill.