I'd like to revive this question from a few years ago with a few specifics. I'm in Raleigh, NC and I've never closed my pool, I simply run the pump for a few hours (usually at night) when temps drop below freezing. According to historical data, we average 51 days a year Dec-Feb when temperature drops below 32 f, and that's usually only for part of the day, and only 8 days below 20 F. With moderate use of the heater we'll swim until the first or second week of Oct, then around the end of Oct I'll bypass and drain the heater, and watch the weather to make sure my pump timer is set to run when temps drop below 32. Opening up in the spring is usually a matter of just bringing the salt level up, balancing chemicals and a shock. All in all it's pretty easy.
Last year was a particularly cold winter and I ran the pump much more, probably twice as often as an average year, plus we had some single digit nights when I was afraid running the pump wouldn't be enough to prevent lines from freezing (they didn't). This had me considering whether or not I should close the pool for next winter. Well, it's almost next winter and I need to decide. Other than a power outage, what factors should influence this decision? Here are a few things I've thought of, but don't know the answers to. Any opinions from more experienced and knowledgeable pool experts is greatly appreciated.
1- Relative cost of running the pump vs. cost and trouble of closing?
2- Is closing the pool better or worse for the liner (which is a whole different question at 8 years old)?
3- What about swg? In the past I've left it on, even though it's not generating most of the winter, should I turn it off?
4- What about sand filter? I keep selector on "filter" for fear of it freezing, is this necessary?
5- I don't have a cover. If I close, do I have to cover the pool?