Sizing a gas heater

[BigSplash]

What is the difference between a gas heater for an inground and an above ground pool?
What size would I need?

[Ready2swim]

We are in the process of building a new pool at our new house but I can say that my old pool was about the same size and we had a 400,000 BTU unit that would heat the pool very quick...it would also heat up your wallet at the same time. The last time I calculated the cost it was around $80 to heat the pool to 85F. When running the Spa (8' dia) it would only take about 30 minutes to heat up to about 102F

I am in Houston Texas and the water isnt very cold to begin with in the winter but it is too cold for me to get into it without a heater.

[tenax]

many companies make a 150,000 btu heater at a minimum..even with my very old (80s) 150,000 teledyne laars, i never have to use maximum heat output to get to between the 85 and 90 we like for our pool..i've just been sizing as i need a new one and my pool is about 15 x 28 and a 125K laars jandy is quite adequate to the task..the H series hayward i looked at starts at 150,000 which will be overkill..plus, i don't hear great things about the hayward..i figure if a teledyne laars can last 20 years plus in my pool..really, can someone expect anything more out of a furnace than that? especially given how tough a pool is on it!

[stualden]

What is the difference between a gas heater for an inground and an above ground pool?
What size would I need?

The manufacturers provide degree-per-hour charts that can help you make the tradeoff decision between heating speed versus heater cost and gas consumption.

You also need to make sure you have sufficient flow for the heater - hotter heaters require greater water flow.