How Does a Solar Pool Cover Work?

By Kami Turky


With the rising prices and environmental concerns, many homeowners are turning to energy-efficient solutions like solar pool covers. But how do these simple covers make such a significant difference? 

By harnessing the sun’s energy, these covers act as natural heaters, warming the pool’s water without needing external power. 

They also serve as a protective barrier, minimizing water evaporation and saving on chemical usage.

In this guide, I’ll walk you through the mechanics behind solar pool covers, explaining their design, benefits, and the science that makes them a cost-effective solution.

Key Takeaways

  • Solar pool covers absorb sunlight to raise water temperatures using tiny air bubbles.
  • These covers reduce evaporation by shielding the pool and increasing humidity above the water.
  • They improve pool cleanliness, reducing chemical needs and preventing algal growth.
  • For optimal performance, consider size, sunlight exposure, thickness, color, durability, UV resistance, and warranty when buying a cover.
  • You can enhance cover benefits with pool heat pumps, solar heaters, and windbreaks like shrubs or fences.

How Do Solar Pool Covers Work to Keep Water Temperatures Up?

Solar pool covers work to keep water temperatures up by absorbing sunlight and converting it into heat, which is then transferred directly to the pool water.

They are designed with a special material embedded with tiny air bubbles, reminiscent of bubble wrap.

You can think of these bubbles as a magnifying glass, amplifying and focusing the sun’s rays onto the water below.

These air bubbles serve a dual purpose in the design and function of the solar pool cover. 

First, as the sun’s rays penetrate the cover, the bubbles capture, intensify, and channel this heat downwards, ensuring efficient heat transfer to the water. 

The direct contact of these heated bubbles with the water means a more consistent and effective warming process.

Beyond this, these bubbles also provide a layer of insulation for the pool. Just as a thermos would keep a drink warm by trapping its heat inside, the air within these bubbles keeps the pool’s heat from escaping. 

This is especially beneficial during the cooler hours of the night or on less sunny days, helping to maintain a steady water temperature even when the sun isn’t shining directly on the pool.

Why Do Solar Pool Covers Minimise Evaporation?

Solar pool covers minimize evaporation primarily because they create a protective barrier atop the pool’s surface. 

When stretched across the water, they act as a shield, reducing the pool water’s direct exposure to the ambient air. 

This simple function makes it significantly harder for water molecules to escape and turn into vapor.

Another critical factor in the evaporation process is the temperature differential between the pool’s surface and the surrounding environment. 

Evaporation naturally acts as a cooling process; as water molecules escape, they carry heat with them. 

Solar pool covers, by design, harness the sun’s energy to warm the water. This means the temperature of the pool’s surface often gets closer to that of the surrounding air. 

So, when the temperature difference is minimized, the rate of evaporation decreases.

Additionally, the wind, which is a major accelerant of evaporation, is effectively countered by the pool cover. 

By shielding the pool from direct wind exposure, the cover curtails the rate at which water molecules are whisked away into the atmosphere.

Lastly, beneath the cover, a microenvironment forms where the humidity levels are higher than the external environment. 

With this increased humidity directly above the water, the air becomes less eager to take in more water vapor. This results in further reductions in the evaporation rate.

Will a Solar Pool Cover Keep My Pool Cleaner?

A solar cover will keep your pool cleaner by acting as a protective barrier against the daily influx of external contaminants. 

With the bubbles facing down, the cover presents a textured surface that makes it harder for debris such as leaves, twigs, and insects to settle. 

Instead of finding a smooth surface to rest on, potential contaminants encounter these bubbles, which often cause them to slide off or be blown away by the wind.

Thus, when it’s time to remove the cover and take a swim, you’ll not find yourself wading through a clutter of fallen leaves or brushing away bothersome insects.

The absence of such debris not only makes for a more enjoyable swimming experience but also reduces the wear and tear on pool equipment. 

For instance, filters don’t get clogged as quickly, ensuring a longer lifespan and more efficient water circulation.

Additionally, the cleaner water means less reliance on chemical treatments. 

With fewer debris introduced into the pool, there’s a decreased need for chlorine and other chemicals to break down organic matter. 

This not only results in potential savings but also creates a healthier swimming environment, reducing the risk of skin and eye irritations often caused by excessive chemical use.

Furthermore, the solar cover’s protective attributes extend to microbial growth. 

By blocking a significant amount of direct sunlight, the cover minimizes the conditions algae need to thrive. 

Algal blooms can make pool water murky and require chemical treatment to rectify. 

Therefore, by regularly using a solar cover, you can prevent these algal outbreaks, maintaining clear water and further reducing maintenance costs and efforts.

What to Look for in a Solar Swimming Pool Cover?

When considering a solar swimming pool cover, you need to look for the following factors:

  • Size Compatibility: Begin by assessing your pool’s dimensions. A cover that doesn’t fit perfectly won’t efficiently retain heat or protect from debris. 
  • Local Sunlight Exposure: If you’re in a sun-rich region, most covers will do. However, for areas with fluctuating sun conditions, you need a cover with more heat retention.
  • Thickness Considerations: Thicker covers may offer better heat retention, they could also be heavier and harder to maneuver. Generally, covers vary from 8 to 16 mil in thickness, so you’ll want to find a balance between performance and ease of use.
  • Color and Design Implications: The color and design of a solar pool cover are crucial. While clear and blue shades facilitate faster heating, darker colors combat algae growth. The bubble pattern design can also influence heat retention and distribution, ensuring that warmth is evenly spread across the pool.
  • Durability of Material: A long-lasting cover is usually made of robust, durable materials. While you might be tempted by cheaper options, they might not offer the same longevity, potentially leading to frequent replacements.
  • UV Resistance: Given the cover’s primary role is to harness the sun’s rays, it’ll be continuously exposed to UV radiation. A UV-resistant cover ensures it doesn’t degrade quickly, maintaining its efficacy and appearance over time.
  • Warranty Assurance: Always check the product’s warranty. This not only gives insight into the manufacturer’s confidence in the cover’s durability but also offers protection against potential defects.

How to Get the Most of out of Your Solar Pool Cover?

1. Use a Pool Heat Pumps

A pool heat pump works by extracting heat from the surrounding air and channeling it into the pool water. This process affects the pool’s temperature through a mechanism called a heat exchanger.

As the ambient air is drawn into the unit, it flows over an evaporator coil containing a specialized refrigerant. 

This refrigerant is designed to absorb and transfer heat effectively. As it captures the warmth from the air, it changes state from a liquid to a gas.

This gaseous refrigerant then moves to a compressor, where it’s subjected to pressure. The compression causes its temperature to rise, making it hotter. 

Following compression, the hot gas is directed into the heat exchanger. At this stage, cool pool water circulates around the exchanger, drawing the heat from the hot refrigerant. 

The water, now warmed, returns to the pool, while the refrigerant, having cooled and returned to its liquid state, circulates back to the evaporator to restart the process.

In conjunction with a solar pool cover, the heat pump’s efficiency is enhanced. The cover acts as an insulating layer, trapping the warmth provided by the heat pump and preventing it from escaping into the atmosphere. 

2. Install a Solar Pool Heater

Of course, a solar pool cover on its own is an efficient tool for passive heating, but its effectiveness can be significantly boosted with the addition of a solar pool heater. 

A solar pool heater works by usingsolar panels or collectors, usually installed on a roof or other sun-exposed location, to capture the sun’s energy. 

This captured energy heats the water that’s pumped from the pool through these collectors.

Once the water is heated, it’s then returned to the pool, raising the overall temperature. 

Thus, combining a solar pool heater with a solar cover offers a dual approach to pool heating. 

While the heater actively raises the water temperature using solar energy, the cover ensures that this heat is retained, reducing the loss of warmth during the cooler hours or days. 

3. Try to Block Wind

While a solar pool cover can somehow mitigate the effects of evaporation, external factors like wind can still impact your pool’s temperature. 

Wind accelerates the evaporation process, leading to quicker heat loss. Consequently, shielding your pool from strong gusts can further enhance the efficiency of your solar cover.

To avoid this, consider implementing windbreaks around your pool area. This can include planting dense shrubs or trees, installing privacy screens, or building fences.


Do Solar Covers Really Heat the Pool?

Solar covers really heat the pool by absorbing sunlight and converting it to warmth, then transferring this heat to the water via embedded air bubbles, ensuring consistent temperatures.

Should You Leave a Solar Cover on Pool All the Time?

You shouldn’t leave a solar cover on the pool all the time. You should take them off at least once a week to release collected carbon dioxide and prevent water acidity.

How Quickly Does a Solar Cover Heat a Pool?

A solar cover raises pool temperatures by 10-15°F in 6 days, depending on sunlight.

How Does a Solar Cover Go on a Pool?

A solar cover goes on a pool bubble-side down, ensuring maximum heat absorption from the sun and effective heat transfer to the water.


As promised, we’ve covered the ins and outs of solar pool covers, shedding light on their efficiency, design, and the environmental benefits they bring.

And if you seek my advice, I’d recommend investing in a solar pool heater alongside your solar cover. 

This dynamic combination maximizes your pool’s heating potential, ensuring comfortable water temperatures even on cooler days.

Do you still have any questions? Feel free to leave them in the comments below.

Kami Turky

Kami is a solar engineer with nearly a decade of experience in researching, testing, and reviewing various solar products. He has also provided technical consultation to several organizations on the best ways to incorporate solar energy into their operations. When he’s not busy helping others find the best solar solutions, Kami enjoys spending time outdoors, hiking, camping, and exploring the natural wonders of his home state.

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