Are you thinking of buying a solar cover for your pool? Solar pool covers, also known as solar pool blankets, involve quite a large investment so it is important to ensure that the expenditure will be worth it for you.
Generally having a solar pool cover will save money in the long run, particularly if you heat your pool using electricity or gas. They will also extend your swimming season and reduce the amount of money you spend on chemicals.
To help you decide whether to buy a solar cover for your in-ground or above-ground pool I try to answer all of the questions you may have so you can make an informed decision.
What is a solar pool cover?
A solar pool cover is basically a large solar blanket. It is similar to very strong bubble wrap that floats on the surface of the pool. It doesn’t need to be attached to the pool as the surface tension, and its weight, holds it onto the pool surface. In 6 years of having a solar pool cover mine has never been blown out of the pool or even been lifted – and we get some pretty strong winds here.
It has bubbles on one side and a strong flat layer on the other. The bubbles help to act as an insulator to stop heat transfer out of the pool.
A solar pool cover is different from a “pool cover”. A pool cover is intended to cover the entire pool to protect it during the winter and/or to prevent children or pets from falling in.
How does a solar pool cover work?
A pool cover works in three ways:
- It floats on the surface of the pool and allows the sun’s rays to enter the pool to heat up the water.
- It acts as a giant blanket and insulates the pool which greatly reduces heat loss, particularly at night and during windy weather.
- As no water is exposed to the air, evaporation is greatly reduced. The process of evaporation is one of the largest ways heat is lost from the pool.
Obviously using the sun to heat a pool is very eco-friendly and can save you money if you use a pool heater.
Pros and cons of solar pool covers
- A solar cover allows the sun’s rays to heat up the water in the pool.
- A solar cover helps to retain the heat in the pool by insulating the pool water from the air above.
- You will save on water as there will be less evaporation of the water as it covers the entire surface of the pool so it will prevent water loss into the air.
- Using a solar cover will extend the period that you can swim in your pool be heating it up quicker in spring and longer into the autumn.
- In some ways it is eco-friendly (and therefore electricity bill friendly) as you will need to use your pool heater less. But of course it is made of plastic so this benefit may be offset in its manufacture.
- You should use less chemicals as the pool being covered helps block UV rays.
- The initial cost is quite high for the cover and a roller. But the roller will last many years so that isn’t such an issue.
- There is extra work involved in removing the cover to swim, but not very much!
- The covers do not last forever so need replacing from time to time
How fast does a solar cover heat a pool?
This obviously depends on many factors such as the weather (is it warm and sunny or cool and cloudy), the air temperature, the wind, the cover thickness and color and even the depth of the pool. See the sections below.
It’s ability to heat the pool up is as much a factor of retaining the heat overnight as it is heating the pool up during the day.
In good sunny weather you can see daily gains of as much as 1-2ºF.
This is hardly rocket science but if the weather is hot and sunny then the pool will heat up much quicker than if it is cool and cloudy. This is the same whether you have a solar cover or not.
If the ambient air temperature is high then the pool will generally heat up quicker and lose heat at night slower.
The wind has quite a large effect on the temperature of the pool as pool water evaporates much quicker in windy weather (and loses heat as a function of evaporation in the same way as you cool down when you sweat and the sweat evaporates). With a pool cover this loss of heat is kept to a minimum.
Cover thickness and color
Solar pool covers vary in thickness and it should be no surprise to hear that when it comes to the best pool solar cover thickness, the thicker it is the overall heat increase is likely to be higher. The lighter the color of the cover, or the clarity, will also result in more heat entering the pool (again no surprise I am sure).
Depth of pool
If you have a shallow pool it will heat up quicker than if you have a deep one. Without a solar pool cover, to retain heat at night, a shallow pool will also lose heat quicker.
My experience of using a solar cover
We live in the Canary Islands, which are off the coast of north Africa, so the climate here is pretty warm generally. We have solar heating panels on the roof which obviously heats the water up quite well, but without a solar cover, much of that heat is lost overnight. We are not masochists, and don’t want to die of shock when we get in the pool, so we want the temperature to be at least 82ºF/28ºC before we put a toe in.
Before we bought the solar cover we usually managed to swim comfortably from mid-April until mid-October. With the solar cover we are often in the pool by early March and swim until mid-November at least..
My pool normally loses 1.5-2ºF overnight without the cover on but hardly loses anything overnight when it is on.
In the summer, on a sunny day (which most are here), without our solar heating on, I often see an increase of 2-3ºF during the day when I have the solar cover on.
Interestingly, we had a power outage for just over 24 hours last summer and I had the pool cover on. My wife and I wanted to swim late afternoon so I rolled the cover back and in we went. The water temperature in the top foot was much higher than the water below by at least 10ºF. Of course the pool pump had not been running so the water had been undisturbed which is why this was so noticeable.
As an aside, it was amazing how the warmer water had such a defined edge to the cooler water below. It was not a gradual transition from hot to cool as I would have expected but a sudden change.
Does a pool warm up faster with the cover on or off?
On a hot, windless day it may be that the pool water will heat up quicker with the pool cover off as more of the sun’s energy will reach the water.
However, the pool cover also helps stop heat loss, and this loss happens quicker in windy conditions, so it may heat up quicker with the cover on.
In my experience it makes very little difference so leaving it on is rather easier than having to keep putting the cover on and taking it off.
Should I take my solar cover off during the day?
If the weather is warm and sunny, with little wind, then you may see a slightly higher increase in the temperature of the pool if you remove the cover during the day. This would probably only be true if you took it off for just the hottest hours of the day. Once the sun starts to go lower then you may begin to lose as much, if not more, heat due to evaporation than you gain from the sun.
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What color solar cover works best?
Pool cover colors can make a difference to the amount of heat that enters the pool and the amount of heat retained in the pool.
Dark blue covers tend to be better at retaining heat than allowing heat to enter the pool.
Clear pool covers will allow heat into the pool the best but will not retain it so well as a dark color.
Light blue covers are a happy medium between letting heat in and retaining heat. That is probably why it is the most common color usually.
There are a few different colors available now (even gold) and some two color covers, with one color one side and another on the other.
What is the best pool solar cover thickness?
There are a few things to consider when it comes to choosing the thickness of your pool cover.
|Thin covers ( 8 mil )||Thick covers (16 mil)|
|– cheaper||– more durable|
|– lighter so easier to cover and uncover the pool||– longer lasting|
|– let more heat directly into the pool||– retain heat better|
|– tear easier||– heavier so harder to cover and uncover the pool|
|– do not last so long||– more expensive|
The normal range of solar cover thicknesses runs from 8 mil to 16 mil. In case you are not aware a mil is one-thousandth of an inch (0.001 inch).
12 mil solar covers are the most popular thickness as they do a good all round job, are easy to handle and last quite a few years.
You really get what you pay for when it comes to solar blankets. Buying cheap can be a false economy.
One of the most popular brands of solar pool covers is Sun2Solar. They produce them in all shapes, sizes and colors.
How does a solar cover go on?
Manual roller or reel: This is the most popular method of removing and putting on the cover. The solar cover is attached to the roller so that when it is would up the cover rolls up around it until off of the pool completely. Most rollers have wheels at one end so that you can wheel it out of the way when swimming if required.
Electric roller: These are similar to the manual roller but are operated electronically at the press of a button.
Manually: In theory it would be possible to pull a solar cover on and off and fold or roll it up manually when not being used. But that would be very difficult and impractical, particularly if it is a big pool. Doing it this way you are much more likely to tear it or damage it in some way so it wouldn’t last very long. It would also be such a pain to put on and take off that you probably wouldn’t bother with it at all after a while.
One of the best solar cover reels is the VINGLI Pool Cover Reel Set which comes with all fittings to attach to a solar blanket and is easy to assemble. It fits all pool shapes/covers.
Should the bubbles be up or down on a solar cover?
Good question as it is not really obvious but the answer to should a solar pool cover be bubbles up or down is – always bubbles down into the water. The bubbles contain air and this is heated up by the sun and the heat is then transferred by the process of conduction. The bubble side is generally the least tough side too having it on the pools surface means it is protected from anything which may drop in the pool.
The smooth side therefore faces upwards. The beauty of it being smooth is that it makes it easier to clean. You can run the hose over it before you remove it from the pool.
Can you use a solar cover in the winter?
Well to a large extent this depends on what the climate you live in is like and whether you want to use the pool year round.
Cold winter climates
If you live somewhere with very cold winters, perhaps with heavy snowfall and hard frosts then the answer is most definitely no. Your solar cover will need replacing much quicker in a climate like this. If your weather is so cold that the water freezes then there is a good chance that the solar cover would be damaged beyond saving by becoming frozen.
If money is no object so you keep your pool heated throughout the winter in such a cold climate, and swim in it, then it may be worth using a solar cover in the winter too. You are unlikely to gain much heat from the sun by keeping it on but the thermal qualities of the cover would help to retain heat. You may just find that the money you save in heating costs covers the cost of renewing the cover should it need it.
Warm winter climates
If you live somewhere like Arizona, Florida or parts of Australia then it may be possible to use the cover in winter to enable year round swimming by keeping the pool warm. Without the extremes of weather the cover is less likely to become damaged.
What do I do?
The climate is great here in the Canary Islands, with the lowest temperatures rarely dropping below 50ºF at night and 68ºF during the day in winter. But there is insufficient sunshine to keep the pool at a temperature that we are prepared to swim in (we hate the cold), even with our solar heating and the solar cover.
So from around mid-November until late February, or early March, I take the cover off and store it. See the next section for tips on storing.
How to store a solar cover in winter
Apart from UV light (more of that in a moment) another thing which makes your solar cover degrade quicker are the chemicals in the pool. So if you just remove the cover and store it then it will have these chemicals, and dirt, still on it. These will continue to act upon the cover while it is stored. So before you store the cover you should wash it with soapy water.
Ideally you should do this in an area large enough to lay it out flat, such as a terrace or a driveway. Lay it out and then hose it down. Afterwards, using a bucket of soapy water wash it with a soft broom to remove as much as you can. Then hose it down again. You should do this on both sides and then leave it to dry completely before rolling it up.
Once dry and rolled up you need to protect it from not only the winter weather but also from UV (Ultra-violet) light. Even the winter sun can produce enough UV to degrade the cover. If you have somewhere inside you can store it, such as a large garage, then that is ideal. If you cannot store it inside then you can buy a cover to protect it quite cheaply in a size to fit yours.
Can you use a solar cover on an above ground pool?
Yes, they work just as effectively on above ground pools as they do on in ground pools. You can even use a roller to wind then in and out as rollers can be purchased which attach to the side of the pool.
Does a solar cover stop the pool getting dirty?
Although some seem to suggest that solar covers do at least help in keeping the pool clean, in my experience, this is not one of their benefits. You always have a small gap between the pool sides and the cover so debris often gets blown towards the edges and then enters the pool.
Also, to keep the cover in good order it is good practice to hose any dirt off the cover before you roll it up so this ends up in the pool anyway while you are using the hose or when you roll it up.
Do solar pool covers cause algae?
Solar pool covers do not cause algae to grow. It may be argued that as they increase the water temperature, and algae grows faster in warmer water, then algae growth can be accelerated by using a solar cover.
In practice I think it makes little, or no, difference. At least I have never had algae growth in my pool since using one for the past 6 years.
Can you run the pool pump with solar cover on?
Absolutely, and you should run it too. Your pool pump should run for the same amount of time each day when the cover is on than when it is off.
The water still needs to be filtered and the chemicals circulated whether on or off and no harm will come to the solar cover when the pump is running.
How long will a solar pool cover last?
Generally the thicker the cover the longer it will last. If you store the solar cover under cover or away from UV rays over winter and take care with it during the summer you may get 5 years out of it but it could be as little as 3 years.
I have to say this is one of my one bugbears with solar pool covers. Their one function in life is to be in full sunshine and float on water containing strong chemicals so why can’t they be designed to withstand that better. Why can’t the manufacturers solve this problem? But that’s just me I guess.
Over time the UV light starts to rot the plastic and it starts to disintegrate. Individual bubbles start to come away (and end up all over your yard). You just have to bite the bullet and replace it at that point.
Other types of solar pool cover
Liquid solar covers
This is a relatively new phenomenon and is basically a form of alcohol which floats on top of the water and prevents evaporation of the water (which is where most heat loss occurs). It sounds rather bizarre but it has been shown to work.
It is very easy to use as every so often you just pour in some more to maintain its effectiveness. Although you cannot swim with a plastic solar pool cover still on the pool (obviously), you can with a liquid solar cover, so there is less work involved. It has been approved safe to use and swim with by the FDA.
Liquid solar covers are not recommended for use in very windy areas though.
It does not damage the filtration system in any way. In fact, as it forms just a thin layer on top of the water, very little of it will actually be pulled through the filtration system.
The most popular liquid solar cover on Amazon is the Natural Chemistry Swimming Pool COVERfree Barrier Layer
Solar sun rings
These are rings of solar blanket, normally with a floatation ring around the outside, which are thrown onto the surface of the pool and act in the same way as a full solar pool cover. It can take quite a few to cover a large pool.
They are easier to remove and replace and also to store over winter since they can just be stacked up.
They do have some drawbacks. They leave areas of the pool surface exposed. Because of that they are less effective than a conventional solar pool cover at stopping evaporation and heat loss.
These are available on Amazon – Solar Sun Rings
My top three pool cleaning tools to make life easier
Dolphin Nautilus CC Plus Robotic Pool Cleaner – the best time saving product on the market. I have never heard anyone say they regret buying one.
Hayward Poolvac Leaf Canister – very useful when leaves are a problem in your pool
Aquatix Pto Pool Step & Corner Vacuum Head – I use this every time I vacuum my pool. It gets where other vacuum heads can’t.
- How to backwash a pool – step by step
- Should a pool pump run continuously?
- What equipment do I need to clean my pool? A beginners guide
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