I have approximately 10,000 gallon below ground gunnite pool with 1.5 pentair pump. We're pretty happy with the setup but would like to heat the pool for year round usage. I know nothing about heaters. Where should I start? Gas? Electric? Solar? And how effective are the different types of heaters at heating water (like I need it heated more than 4 degrees)? I realize we're probably adding a new utility bill on by doing this, but.. I really enjoy my late evening swims after I get the kids to bed so it's something I'm willing to pay for.