Heating your pool is largely a personal decision.
There are many pools that go unheated for the whole season. Some hardy people enjoy 70º F. water. Some like their pool at 85º. (Do not keep your pool at 90º as this may cause liner wrinkling and void the warranty). Most people like their pool temperature between 78º and 82º F. There are many ways of achieving this, including (in order of percentage of sales) Natural Gas, Heat Pumps, Solar, Propane, Oil, and Electrical Resistance.
First of all, we wish to note that we highly recommend the use of solar blankets when it is cool. Not using a solar blanket is comparable to heating your home with the windows open. When the air temperature drops more than 15ºF/8.5 ºC. below the pool temperature, your heater may not be able to keep up with the heat loss without the use of solar blanket. 70% of heat loss from a pool is through evaporation, 20% from re-radiation and 10% through convection. A product called the “Turbo Tropical Fish liquid solar blanket” promises to reduce evaporation by 50%. It disperses a liquid into the pool that floats on the surface and creates a pool friendly, invisible cover. It will not affect the chemical balance (pH, alkalinity), plumbing, filtration, vinyl liner or any other pool surfaces in any way. And it certainly is easier
to use than a solar blanket.
Natural Gas Heaters are for people that want instant heat at the flick of a switch. A cubic meter of natural gas at 2009 prices costs $.34 and contains 36,000 BTUs. Therefore, a 250,000 BTU heater consumes 6.94 cubic meters per hour. This means it costs $2.36 per hour to operate the heater. The definition of a BTU is that amount of heat that it takes to raise 1lb of water 1º F. A 16 x 32 pool holds 60,000 liters or 132,000 lbs of water. Most natural gas heaters, when new, have an approximate 80% efficiency rating. That means that of the 250,000 BTUs per hour it consumed only 200,000 were captured by the water. In one hour your heater will bring the temperature up 1.5º F.
Heat Pumps have really come of age.Today, with the advent of Titanium Heat Exchangers, these heaters are nearly impervious to pool water chemistry, making them very reliable. Titan Heat Pumps will typically provide 4 to 5 units of free energy for each 1 unit of energy consumed to operate, depending on the air temperature and humidity. Model Ti2 made by Titan has a rated output of 85,000 BTUs per hour and a running amperage of 16 amps at 230 volts. This means that it consumes 3.680 kilowatts per hour. 3.68 kWh times $0.113, current cost of electricity, equals $.416 If we are to compare it to the Natural gas heater, above, which produces 200,000 BTU then
we must multiply the $0.416 times 2.35 (200,000 / 85,000) which equals $0.98.
Comparing the two above heaters, we see that a 250,000 BTU Natural gas heater costs $2.36 per hour and will raise the temperature of a 16 x 32 pool 1.5º F. A Ti2 Titan heat pump will cost $.98 to raise the same pool 1.5º F. but it will do so over a period of 2.35 hours. The heat pump is therefore 2.4 times ($2.36 / $.98) less expensive to run than the Natural gas heater. The only drawback to using a heat pump is that it is slower to initially heat the pool, taking 2.35 times longer than natural gas, depending on the air temperature/humidity.
Over a whole season the savings are considerable.
Solar heating is inexpensive to run but the most expensive to set up. You are also at the mercy of the weather. If the sun is not shining, you have no heat. The following is basic information for sizing and locating a solar system. At our latitude we receive approximately 250 BTU per square foot per hour. Most commercially available swimming pool solar panels are 80% efficient at collecting that heat. That means they collect 200 BTUs per square foot per hour.
Solar systems are sized according to the surface square footage of the pool. If your panels are facing south and at a 30º angle then you need 50% of the square surface of the pool. If they are facing west then you need 75%. Do not install panels facing north or east. A 16x32 rectangular pool has a surface area of 512 sq. ft. With a south facing roof you need 256 sq. ft. of solar collectors or approximately six 4x10 panels. 240 sq. ft. times 200 BTU per sq. ft. gives you a potential of 48,000 BTUs of heat per hour. Solar systems collect most of their heat between 9:00 am and 4:00 pm. This gives you a potential of collecting (7hours times 48,000 BTUs) 336,000 BTUs per day. This will raise the temperature of the pool by 2.5º F.