Are gas pool heaters the best option for heating you pool. Well it depends ....

1. Are Gas Pool Heaters A Good Buy?
Although lots of gas pool heaters are sold they are not as energy efficient
as alternatives like heat pumps or solar heating systems so buying one
might be considered environmentally unfriendly.
However gas pool heaters are popular because they have a number of
advantages:
• Low costs to purchase and setup - Obviously the cost depends on
the size of your pool but gas pool heaters can be obtained well
under $1,000 to heat an above-ground pool and for an in-ground
pool under $1,500. You will have to pay to have the gas and electric
side of things professionally installed but the rest of the installation
should be within the capability of someone who is reasonably
handy.
• High capacity - One major benefit of gas pool heaters is that they
have a high capacity (up to 400k BTU/hr for residential pools) and
can therefore heat the water relatively quickly. Therefore they are
ideal if you only heat your pool from time to time.
• Energy Efficiency - Most residential gas pool heaters now have an
energy efficiency rating of between 80 and 85% a figure which has
improved considerably in recent years. However you can buy a gas
heater with an efficiency rating of 95% such as the Jandy Hi-E2.
• Reliability - Although gas heaters are improving all the time this is a
tried and tested technology. A properly maintained heater should
give you many years of worry free pool heating.
• Independent of the weather - Neither solor heaters nor heat pumps
will work in all conditions but a gas heater will.
Gas pool heaters usually are available for either natural gas or propane. In
terms of performance it does not matter which you use but in terms of
cost there is a major difference. Propane can cost up to twice as much as
natural gas so is never the preferred option.
You can buy both electronic and millivolt ignition gas pool heaters. The
former are more popular as they feature electronic ignition and electronic
controls. However to power these functions they need an electricity
connection. Millivolt heaters, on the other hand, use a pilot light ignition
system (which wastes energy) and have more basic controls but have the
advantage of not needing an electricity connection.
Popular heater ranges include the the Raypak Digital Heater, Jandy
Legacy and Hayward H Series.
The main competition these days comes from pool heat pumps. These are
considerably more expensive to buy and are not as powerful. They work
on electricity which is more expensive than gas and they don't operate at
low temperatures. Their big advantage is that they move heat from the air
to the water rather than generating it. This gives them an energy
efficiency rating of several hundred percent and makes them cheap to
run.

2. If you heat your pool constantly during the season then you should
certainly consider a heat pump. If you do not heat your pool all the time
then a gas heater will be your best option giving you the best balance
between purchase/installation costs, heating power and running costs.