Should you buy an electric pool heater (heat pump) or a solar pool heater? Each has its pros and cons, some of which are shared.
Electric Heat Pump Pool Heaters
Electric heat pumps are popular in Florida, and for good reason. Since heat pumps use the latent heat in the air to heat your pool, warm Florida daytime temperatures are complementary to heat pumps. The efficiency of a heat pump is related to the air temperature vs. the pool water temperature. When the outside temperature is relatively high, the efficiency can by very good. For one unit of electricity (kWH), you can get about 6 times the heating energy (BTU) into your pool water. However, as the ambient temperature drops, the efficiency of an electric heat pump drops. In fact, at a certain temperature, heat pumps will stop working, or will be astronomically inefficient. That means you could be using electricity and barely putting any heat into your pool. If you want to swim (or enjoy a spa) on a cold morning, the heat pump may be ineffective overnight.
Some heat pump manufacturers and dealers tout the “dollar-a-day” cost to operate a heat pump. However, when you read the fine print, the temperatures reached are often not warm enough for many bathers, there are disclaimers about excluding days below certain temperatures, and the cost is an average that includes days when heating is not necessary. If you think a heat pump that runs all the time will cost you $365 a year to operate, think again. You could easily rack up a $365 bill in January alone. The bottom line is that heat pumps cost the most to operate when you need them the most, i.e. when the pool is the coolest.
Electric heat pumps take several hours to heat up a pool, providing at best a couple of degrees of heat rise per hour. If you run your pool pump only during the day, you heat pump will start over each day to recover heat lost overnight. However, for reasons stated above, it does not make sense to attempt to heat your pool overnight unless you absolutely need warm water in the morning (use a cover, and still be ready to pay!)
Solar Pool Heaters
Solar pool heaters have the distinct feature of being the only pool heating option that involves no direct operational costs. You can experience heated pool water every day of the year, with temperatures reaching up to 15 degrees Fahrenheit above that of an unheated pool in some cases. Typical daily maximum temperatures exceed that of unheated pools by about 10ºF, or 15ºF if using a pool cover. In Southwest Florida, that is good enough to provide almost year-round swimming enjoyment.
On the downside, if you are looking for even warmer temperatures, or want to quickly heat a spa (solar heaters can take a couple to a few hours to heat up a spa to 100ºF on a good day), a solar pool heater may not be reliable enough for you. If you want to virtually guarantee a set temperature each day, solar pool heaters will not be the best choice. After all, it’s a weather dependent technology! On the other hand, an electric heat pump can’t provide a guarantee either (see above). Like electric heat pumps, solar pool heaters will result in the warmest water later in the day after the sun has had a chance to work its magic.
So why are solar pool heaters so popular in Florida? While heat pumps promise relatively energy efficient pool heating, there is still a cost involved, and that cost is hard to anticipate. Solar pool heaters will heat your pool every day of the year without operating costs. Solar pool heaters also last about twice as long as a regularly used heat pump, and the maintenance costs are far lower (virtually nil in most cases). Since the initial cost of a solar pool heater is similar to the cost of a quality heat pump, many people conclude that the ongoing costs of a heat pump will likely prevent them from using it often, which translates into less enjoyment of their pool.
Should I Choose an Electric Heat Pump Pool Heater or a Solar Pool Heater?
The choice is yours. Heat pumps provide fairly reliable temperatures most of the year, but at a cost, as long as you plan ahead. Solar pool heaters reliably heat your pool a certain number of degrees above an unheated pool every day of the year, but cannot achieve a set temperature if it exceeds the capability of the system. Solar pool heaters and electric heat pumps are both weather dependent technology in different ways, and at some times solar pool heaters and electric heat pumps may not be able to work at all. For example, solar pool heaters do not work at night, so pool heating needs to be done during the day. Heat pumps don’t work when the temperature gets very cool, and if they do they cost an arm and a leg to operate.
Why choose if you can have both?!
Solar pool heaters can complement an electric heat pump very well (or vice-versa). If you budget allows, you can install both systems. The solar pool heater will do the heavy lifting by heating your pool every day and maintaining higher average temperatures so your heat pump will run less (far less). Automation systems can make this marriage work seamlessly. It is a common situation to have a homeowner or commercial owner that is tired of high electric bills install solar panels to reduce the electricity costs. In fact, in many situations where we add a solar pool heater to an existing heat pump, owners report never using the heat pump again, or use the heat pump only for spa heating.
In the end, the combination, or hybrid system as we call it, can be the best of both worlds.