I live on the Cape (in MA) was wondering what it would cost to get a heater for our in ground pool that is 16 x 32 salt water pool. I have seen that they say to get a 250,000 btu for the pool but what is the cost to run a heater? Which one should I get a natural gas or propane? monthly cost to run the heater. Just look to warm up the pool in the spring April, May part of June temp to only 80 then turn it off for July and Aug then back on for Sept Oct.or must it be on all the time to it to be cost efficent? Trying to get my husband to put in a heater and he keeps saying it cost to much..like $500 a month for just the NG ? I was thinking propane? Need some help in the argument dept if so facts thanks you