Those of you with a pool, how much are your maintenance costs?

In light of the fact we're not in a position to go full 'Australian dream' and buy by the coast, we're considering purchasing a property with a pool as there are some around within our budget, but I was just wondering what the ongoing costs might be like? I know it depends on the size/setup/water purification type of course but it would be good to understand what we might be getting into.

Also, do you use your pool much in winter, has anyone got into colder weather swimming in theirs?