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Swimming Pool Heating Guide

Categories: Energy Efficiency, Heaters
 Owning and maintaining a swimming pool is a major expense in terms of both time and money, and thus property owners are always looking for ways to maximize return on that investment.
Anyone can appreciate the value of a pool in the hottest days of summer, but for most locations in the U.S. the dog days are just a small percentage of the year. Does it make sense (economically or otherwise) to commit major resources to a pool if its annual usefulness is three months or even less? Most people would say no, and so to get a longer season out of their pool they typically turn to various heating methods to keep the water comfortable over a longer stretch of the calendar. This allows for year-round swimming (if so desired) or at the very least a season that extends into the spring and/or fall.
But once you’ve decided a heating system works for you, what’s the best way to go? There are heat pumps, gas heaters (of several varieties), solar heaters, conventional electric models and more to choose from, and each option has its own distinct pros and cons. It may seem like there’s just too much information out there to make an intelligent individual decision, but as in most cases understanding your own needs is the best place to start.
What’s the ultimate goal?
A common assumption pool owners make is that brand-new hardware is necessary to keep water sufficiently warm. Yet often, really, it comes down to your location and your priorities. An owner in Arizona, for instance, who simply wants warmer swimming water for cooler fall nights could save money and shopping time by investing in a solar cover or heat squares as opposed to making a major heater investment. What could be more sensible than making use of a plentiful resource (desert sun) to achieve this basic goal?
A family with small children could also be well-advised to try alternatives to heaters, as the kids are likely to be preoccupied with school and other activities in the non-summer months and parents don’t always have the time (or money!) to make an investment that could be largely ignored over time. But if your own needs are more involved (or if you don’t happen to live in Phoenix or Palm Springs), heating equipment may be more of a necessity than a nicety, and there’s no need to be in a fog over what your options are.
Consider the alternatives
The most popular choices in the market today are heat pumps and gas heaters, and each option has its advantages and drawbacks.
Heat pumps are typically more expensive than gas heaters, but they are far more efficient to operate and thus produce substantially lower utility bills while being easier on the environment. Their simpler design (capturing existing heat from the air as opposed to creating it) also generally leads to a longer life span, roughly 10 years according to industry studies.
Gas heaters are popular partly because they have a lower price tag than heat pumps and they are very fast. This is obviously a draw for consumers in colder climates and those who prefer the flexibility of heating their pool relatively quickly for a specific event. But as you might expect, this level of activity takes its toll – gas heaters generally need replacing every five years or so, which is roughly twice as often as heat pumps.
These heaters are generally fueled by propane or natural gas. Propane heaters create more BTUs with the same amount of intake than do their natural gas counterparts, but propane generally is much more expensive. Pool owners who live in higher altitudes will generally have to pay more for gas heaters as well, since maintaining the proper ratio of intake oxygen requires more internal equipment.
The choice of a propane or natural gas heater typically comes down to personal preference (propane is ‘richer’ in energy and thus requires less gas while natural is considered more environmentally friendly) and the availability of each gas locally. For a given line of heaters, however, propane and natural gas models that produce the same BTUs per hour are often similarly priced, if not identically so.
Another consideration when evaluating heat pumps and gas heaters is determining what size (expressed in BTUs) is right for your pool. Once again, geometry rears its head in pool maintenance! But the idea is fairly basic:
  • Find the surface area of your pool (20’ x 30’ would be 600 square feet, for instance)
  • Determine how much you want to raise the water temperature (from 70 Fahrenheit to 80 Fahrenheit, say would be 10)
  • Then multiply the square feet, by desired temperature increase, then by 12 (Why 12? Because the expertise of generations of pool professionals said so!)
  • In this example, the result, 72000 (or 600 x 10 x 12) represents the required heater output (expressed in BTUs per hour), so the pool in question would require a 72K BTU heater.
Many manufacturers, in fact, offer sizing charts to help customers with the math involved in picking out the right model, such as this heat pump guide from Raypak.
Traditional electric heaters still hold a place in the market as well (usually when gas heating is not an option), but their desirability has faded over the years due to the energy efficiency of heat pumps and the speed of gas heaters.
But even in this niche of the market, suppliers are eager to help potential buyers, as evidenced by this electric heater sizing chart from Coates.
But what about solar?
At this point, many pool owners would mentally put themselves squarely in the camp of heat pumps or gas heaters – and overlook another solution that may be all around them. Solar panels are a far less expensive method for heating pools, and if you’re in an area that offers plentiful sunlight a healthy percentage of the year, they could be perfect for you.
If that’s the case, a drive through the neighborhood will probably let you know. Solar panels placed on rooftops collect thermal energy throughout the day, which is then used to warm water through the pool’s existing pump. That means minimal additional hardware, zero unpleasant jumps in your power bill, and no worrying about whether you’re actually buying the right model.
The downside, of course, is that few areas of the country can consistently count on day after day of sunshine, and solar panels lack the speed of gas heaters and heat pumps in any case. However, for many consumers they’re an ideal option based on - once again - particular situations and needs, and are becoming more and more commonplace.
If solar panels don't make sense for a particular pool owner, solar blankets can be a huge benefit for virtually anyone interested in using the sun to conserve warmth and money. For many users in warmer areas these blankets work fine on their own, but when used in conjunction with the heating options we've discussed they can dramatically cut energy demand and keep pools comfortable for much longer at a negligible cost. Check our our blog post on solar covers here to learn more.
Still have questions about the right heating option for your swimming pool? We're here to help! Feel free to comment below or give us a call and we'll do everything we can to get you the info you need!
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Pool Supply Unlimited is an e-commerce company that loves water. We love to pump it, filter it, heat it, chlorinate it, light it up and stare at it while we're barbequing a fat, juicy steak. There are real pool professionals working here. Our guys have seen thousands of pools in their careers, no exaggeration. We are based in San Antonio, TX and can land most products to your door (within the 48 contiguous states) in less than a week.
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