Although many different types of spa heaters exist in the market, gas and electric spa heaters are the most popular and easily available. Heaters come in different sizes, and the right heater depends on the size of the pool or spa, the maximum temperature desired, and whether the device needs to heat both the spa and the pool, or just one. In addition to gas and electric heaters, other options include fossil fuel heaters that are run on propane or oil, heat pumps, and solar heaters.
Natural gas and liquefied petroleum gas (LPG) are usually easily available, so gas heaters are the most common option for heating swimming pools and hot tubs. Easy to regulate, gas heaters are ideal to set the particular temperatures required in pools and spas. Natural gas fueled heaters are the fastest, warming up the water within a few minutes, half the time taken by most electric heaters. Popular for quick and consistent heating, gas heaters are also the cheapest and most convenient to use. Low running costs, minimal maintenance, and instant availability make it a good choice to heat a pool or spa.
Heaters fueled by heating oil or propane cost more than gas spa heaters. Propane-fueled heaters must be handled with care; the gas is heavier than air, so leaks do not easily disperse, posing a risk of explosion. Air-to-liquid heat pumps, which use warm ambient air to heat the water, are another common option to heat up a pool or spa.
Like gas heaters, electric spa heaters are built as stand-alone units. Water flows from the pump to a filter, and then to the element tank for heating. While large and commercial heaters come with a separate cabinet, portable electric heaters common in small spas or pools with a limited power supply have heaters mounted to other equipment, and controls integrated into the common spa control panel. Due to high running costs and comparatively longer time taken to warm up, electric heaters may be impractical in large spas.
Many owners are investing in a solar pool or spa heater, which can significantly reduce heating bills. After the initial investment in the solar heating system, there is a very low operating cost and minimal maintenance. Made up of light-weight plastic, unglazed solar collectors connect directly with the existing pump system and can be easily rolled up and stored when the season ends.