How To Heat A Pool Without A Heater


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With all of the attention on using renewable resources, you may want to go green by installing a solar pool heater. Getting free heat from the sun is better for both the environment and your wallet. This guide will help you learn the basics of solar pool heaters.

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Step by Step


Step 1

A solar pool heater is a very simple system comprised of solar panels and a pump. The pump circulates pool water through the heated panels and continuously returns warmer water to the pool until the desired temperature is achieved. On average, the rise in temperature will be 2 to 5 degrees F for each circulation of water through the solar system. It normally takes from 8 to 12 hours to cycle all of the water in your pool so you can expect an overall temperature rise of 5 to 15 degree F after several days of sunny weather. To get the maximum benefit from solar panels, they must be positioned to receive as much full sun exposure as possible, keeping in mind that afternoon sun is stronger and therefore better than morning.

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Step 2

The initial investment for a solar pool heater will vary depending on the size and type of pool, and whether or not you hire an installer. After that, there’s relatively little expense involved with this method of pool heating aside from possibly needing to repair or replace a panel or connecting parts in the future. You don’t have to worry about gas lines or corrosion of equipment that could happen with gas heaters and heat pumps. In general, solar panels will last 15 to 20 years without the need for more than basic maintenance such as winterizing.

Step 3

If you are replacing a gas pool heater with solar, you will typically see a return on your investment within two to four years, depending on your location, length of swimming season and the temperature you want to maintain. Once you’ve recouped the cost of the solar pool heater and its installation, there is usually no additional cost to run it since it’s tied into your pool pump which you’re already running. Even the addition of a booster pump, which might be necessary for some installations, should only cost a few extra dollars per month. So if you’re wondering how much money you’ll save using solar, the answer is whatever you’re currently spending to heat with gas, after you recoup the initial expense of the solar pool heater.

Step 4

For in-ground pools, the total square footage of solar panels should equal at least half of the pool’s surface area. For instance, a 20’ x 40’ pool is 800 square feet so you’d want a minimum of 400 square feet of panels. If you live in a very sunny region like the southwest or Florida, this calculation should be sufficient. But we typically recommend going with a bit more than this to make sure you have adequate heating, especially in colder and/or less sunny climates.

Step 5

Solar pool heaters for in-ground pools are usually roof-mounted either horizontally or vertically, depending on the system you choose. The smaller panels are vertical and come two sizes, either 2’ x 10’ or 2’ x 12’. The horizontal panels are 2’ x 20’. The size and shape of the available area on your roof will determine which panels will work best. The ideal location for solar panels is a south-facing, pitched roof closest to your pool equipment. West-facing would be the second choice, east the third choice and north the least desirable. Don’t neglect measuring the roof to make sure the panels will fit. You also need to pay attention to trees or other structures that might shade the section of roof you choose since your solar heater is dependent upon receiving direct sunlight.

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Step 6

Once the solar panels are mounted to the roof and connected to each other, you would attach the plumbing to connect the panels to your pool equipment. This would not be included with the panels since every installation is unique; you can purchase the necessary plumbing at a local hardware supplier. The pump required for a roof-mounted solar pool heater will depend on the size of the system and distance from the pump. In general, a 1 - 1.5 horsepower pump will be sufficient for installations up to 30 feet away from the equipment location and one story high. Larger systems and/or remote installation may require a higher horsepower pump. We recommend that you contact the manufacturer of your pool pump before purchasing a solar pool heater. Their technical support should be able to advise you regarding which pool pump you'll need for your particular installation.

Step 7

Choosing solar pool heaters for above ground pools is a little different than for in-ground. Generally you would need 1 – 6 panels depending on the pool size. For above ground pools, solar panels are typically either 2’ x 20’ or 4’ x 20’, depending on the system. Economy solar pool heaters have the smaller panel size and are used mainly for supplemental heating. Deluxe solar pool heaters have larger size panels which offer complete pool heating. The other main difference between economy and deluxe solar systems is the header size. The header is the opening the water passes through. The larger, 2-inch headers on a deluxe panel are considered better as these do not slow down pool circulation and insure better heat transfer to the water. Smaller 1-1/2-inch headers which are found on economy panels are less efficient and can reduce water circulation in your pool.

Step 8

The panels for above ground solar pool heaters are often installed on the ground or a rack right next to the pool. They connect to the pool filter with flex hose. Water exits the pool from the return fitting, passing through the pump, into the filter and then through the hose into the panels. As water passes through the panels, which have been absorbing heat from the sun, it is heated and then returns to the pool through an inlet fitting. This cycle will be continuous as long as your pump is running. You can install an optional bypass (or diverter) valve to close off water to the panels.

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Step 9

If you decide to mount your above ground panels on the roof, you’ll need to make sure your pump will provide enough lift. As with the in-ground solar heaters, a 1 to 1.5 horsepower pump can usually handle installations up to 30 feet from the pool and one story high but it’s a good idea to check with the pump manufacturer to be sure your pump will be sufficient.

Step 10

There are a few things to consider when installing a solar pool heater for either in-ground or above ground pools. If you live in an area with high winds or frequent storms and still want to mount panels on your roof, you'll want to purchase a hurricane mounting kit which provides extra hardware for installation in high wind applications. One kit is needed for each pair of panels with one additional kit required to complete the hurricane mounting. For example, a solar system consisting of 8 panels would require 5 kits. Solar panels can also be mounted on a rack on the ground which is fine as long as the sun exposure is good and the rack is not in a high-traffic or vulnerable area. You'll want to keep children, pets and other potentially destructive beings away from the panels. Ground mounting may be preferable in areas subject to wind, storms, hurricanes, etc.

Step 11

The main drawback to solar pool heaters is that they're entirely dependent upon the available heat from the sun. You can’t generate more heat like you could simply by running a gas or electric heater longer. So if you have a stretch of cloudy days with poor sunlight, you will not have much if any heat available. For those of you who are used to just turning on a gas heater or heat pump, this may take some getting used to.

Step 12

As with other types of heaters, it is recommended to use a solar blanket along with your solar pool heater otherwise you may end up losing much of the heat gained during the day. These plastic covers are made of a material very similar to bubble wrap and are designed to retain heat. They also shield your pool from cool winds and lower nighttime air temperatures which draw away heat. Solar covers float on the surface of the water when the pool is not in use. They come in blue and clear materials, the blue being thinner and less expensive. The clear solar blankets are preferred because they’re not only thicker but also allow more sunlight to pass through the material. This helps to increase your pool temperature as well as prevent the loss of accumulated heat.

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Step 13

The installation of a solar cover is fairly simple since it just needs to rest bubble side down on the surface of the water and does not have to be attached to the deck or pool wall. But since these covers can be cumbersome and difficult to move when wet, many pool owners employ solar reels. The reel is a long tube attached to a base with a hand crank that is used to easily roll up the solar blanket and store it out of the way when the pool is in use. For in-ground pools, a solar reel would sit on the deck at one end of the pool and extend across the width of the pool. Straps are used to attach the solar cover to the reel. Some reels have casters so that the entire unit can be easily moved. Aboveground pool solar reels are similar except they attach to the top rail of the pool wall and are designed to swing to the side when you want to use the pool.

Step 14

An alternative to the traditional solar cover is the Solar Sun Ring. This UV-resistant poly vinyl ring measures five feet in diameter and floats on the pool surface. It is recommended that you use enough rings to cover 70% of your pool surface. Magnets spaced along the outer perimeter attach the rings together. The magnets easily come apart if someone falls into the pool, making Solar Sun Rings safer than regular solar covers. These rings can increase your pool temperature by an average of one degree per day. In warmer areas of the country, you can get up to 3 degree temperature rise daily. The clear top side attracts the sunlight and the blue underside transfers the heat into the pool or spa.

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Step 15

Solar pool heaters can be automated with a solar controller which provides a variable thermostat much like the one you use in your home. You can set the desired temperature for your pool and then the controller will open and close a motorized valve to control water flow to the panels. By way of temperature sensors, the control monitors both the outside air and pool water temperatures and will open the valve when the sun is hot enough to provide heat. It will also close off flow to the panels when the weather is cloudy or windy to prevent cooling of your pool. Most solar controllers will also allow you to control other functions such as your pool pump, lights or a booster pump for an automatic pool cleaner. The most popular solar controller brands are Goldline and Pentair (Compool).

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(1 to 14 of 14)

 Posted: 10/29/2019 

I like the idea of the solar pool rings to keep my pool heated in the winter in Southern California. However I am concerned with The pool losing a lot of the heat the generate by the rings because they don’t cover the entire pool. Is the correct? How much heat is generated and retained by the rings compared to a full solar cover?

InyoPools Product Specialist  Posted: 11/4/2019 

The solar rings retain about 60-70% of the heat that is generated during the day. A full cover will retain more than 90%.

 Posted: 3/29/2019 

I have an inground pool. As an alternative to installing solar panels on a roof can I install the panels 20-30 ft away from the pool if I have room in my yard?

InyoPools Product Specialist  Posted: 4/1/2019 

Yes, you can install the solar panels closer to the ground. The main concern will be sun exposure, shadows from large trees and your house will need to be taken into account when scouting for the right locale.

InyoPools Product Specialist  Posted: 8/11/2017 

tcdinwilm - I would buy the largest gas heater you can afford. If you have access to natural gas, go with that. It is generally much cheaper than propane. A larger unit will heat your pool faster and will help extend your swim season further. Be sure to also buy a pool cover to help maintain the heat you've generated.

 Posted: 8/8/2017 

I live in Wilmington,NC. We do get some chilly weather but average January is 50-60 degree days dropping into upper 30's at night. Building new house with pool/spa combination approx 14x 26 with 6' at deepest. Please, your suggestion to heat all this?

InyoPools Product Specialist  Posted: 11/21/2016 

NH-Terry - If the snow covers your solar panels, they will get no heat from the sun and you will end up cooling your pool. Some people in the south run their solar panels during the night to help cool their pool when the water is too warm. Even without the snow, the sun is weaker in the winter and any heat you may collect from the sun would be lost to the colder temperatures.

 Posted: 11/18/2016 

Hi I have an indoor pool that is approximately 20K gallons circa 1985. It is currently heated to 84 degrees with a large propane pool heater. As I live in a region that snows in the winter does it make sense to have a solar heater. Will freezing winter weather actually rob the pool of heat when circulating the water through the solar panels? My propane bill is rediculous but we like to swim in warm water especially when it is freezing outside! Thanks, Terry

InyoPools Product Specialist  Posted: 6/1/2016 

Michelle - Here's a link to a Heat Pump Calculator by Raytheon. It determines the heat pump you will need for your area and for the number of months you want to operate. It also compares the cost of running this heat pump against operating natural gas or propane heaters. Just follow the instructions at the top of the chart.

 Posted: 5/31/2016 

I am looking for a way to heat a 28000 gallon in ground pool. I live in NY, so am only using the pool 4-5 months/year. What is the best/most cost effective method?




InyoPools Product Specialist  Posted: 5/17/2016 

Jerry -I think the answer is that there is no ideal flow rate. With high flow, the water that is exiting the solar panels is cooler than the water exiting the solar panels at a slower rate because the faster moving water does not have as much time to collect the heat. For a given period of time, warm water at 60 GPM will transfer as much heat as hotter water at 30 GPM. Effectively, there is no difference in heat transfer.

 Posted: 5/16/2016 

I am looking for the flow rate for ideal heat to water transfer in a 12 by 24 aboveground pool with 2 x 20 solar panels. Please help

InyoPools Product Specialist  Posted: 6/2/2014 

Fancypants40 - The most cost effective means of heating your pool is with a solar panel as shown in this guide. Once installed there are no operational costs. The next least expensive option is a heat pump.

 Posted: 6/1/2014 

We have a 16x32 built in pool.....It is screened in....and cold.
What is the most cost effective? (Cheap) :0) way of heating it?