I'm very very happy with my Sta-Rite heater. As heaters go the larger the better. Mine is a 333k btu natural gas model. Solar and heat pumps weren't really a good option since I like to heat my spa quickly in the middle of the night

All brands have their problems though. The one that was the worst in my research was Hayward and the best was Sta-Rite (probably because there aren't many around) I do not regret my purchase........yet (fingers crossed)