We are currently looking at replacing a broken spa heater with a Hayward 250,000 BTU Gas Spa Heater (but someone mentioned the pool and spa were heated at one time) for the community pool and the HOA asked for input from the community. They received a quote for the above option but I thought there must be a better alternative as we live in Arizona that uses a mix of solar and an electric heater. The goal would be to heat the spa for sure at the lowest cost possible utilizing solar and an electric heater with the possibility of heating the pool just slightly during the summer. The spa gets used year round but the pool is still very chilly even with us hitting 100+ degrees already. We have no option for a cover of any kind and I believe the pool is somewhere between (or around) 10x16 or 12x24 with it going from 3ft to 5ft depth (rectangular pool). The spa is in the corner of the pool and is probably 6ft in diameter.
My thoughts would be using the solar to heat the spa water (and potentially the pool water) during the day as we have a restroom building next to the pool and use the electric heater to augment the temperature as needed. Currently I believe they estimated the spa costing the HOA $800/month using the old gas heater and the new unit should be more efficient but there is still going to be loss in heat using gas. Any ideas? First time posting as well so go easy on me!