How Fast Does a Solar Cover Heat a Pool?

By Kami Turky


As soon as you get your hands on a solar cover, the question of its efficiency naturally arises. 

A solar cover acts like a magical heat magnifier for your pool, absorbing sunlight, trapping heat, and elevating the water temperature. So, how fast does this process happen?

A solar cover heats the pool in about 6 hours, though the exact timing can vary. This variance depends on factors like cover thickness, the pool’s temperature, and the amount of direct sunlight.

In this article, I’ll walk you step by step through the ways that solar covers can effectively heat your pool, the varying types, and how they can be a pivotal part of your energy conservation strategy.

Key Takeaways

  • Solar covers, constructed from materials like polyethylene, cut down on evaporation, thereby conserving energy, and they can save up to 70% in heating costs.
  • They heat pools, with variations like solar blankets able to boost the temperature by 10-15 degrees, but factors such as thickness and external temperature affect efficiency.
  • Solar covers include 3 types: Solar blankets, solar rings, and liquid solar covers, each with a unique design for heating and evaporation control.
  • While beneficial for retaining heat and minimizing heat loss, solar covers cannot replace solar heaters, which actively collect and convert solar energy.

What Is a Solar Cover?

A solar cover is a special type of covering for swimming pools designed to minimize evaporation and thereby conserve energy. 

By acting as a barrier between the pool’s water and the open air, this cover can significantly reduce the loss of heat and moisture.

For outdoor pools, the water evaporation process leads to a substantial energy loss—precisely 1,048 Btu for each pound of 80ºF water that transforms into vapor.

To fight this, the solar cover serves as a protective shield. It’s made from materials like UV-stabilized polyethylene, polypropylene, or vinyl, designed specifically for the demanding task of outdoor pool conservation. 

When it comes to indoor pools, the landscape changes slightly but the role of the solar cover remains important.

Unlike outdoor pools, indoor pools aren’t exposed to direct environmental factors like wind and sunlight, but they still can suffer from energy loss of up to 70% due to evaporation.

Also, humidity control within an indoor pool’s surroundings can be a thorny issue. 

A solar cover comes into play as a vital tool in managing this problem – by reducing the evaporation process, it helps maintain an optimal level of humidity within the pool are.

This results in cost savings of up to 50%–70%. By retaining heat and moisture, the cover reduces the need for additional heating, allowing for significant reductions in pool heating costs.

How Fast Does a Solar Cover Heat a Pool?

A solar cover heats the pool in about 6 hours, although the exact time varies. Your pool can get warmer, certainly, with a solar pool cover, but how much warmer hinges on various elements.

Not all solar pool covers are designed to heat a pool. For instance, liquid solar coverings serve more as a barrier to keep warmth rather than raise the temperature.

On the other hand, a solar blanket acts as a more efficient means of heating, with the potential to boost the water temperature by 10-15 degrees in one sunlit day.

You can expect about a 5-degree increase within the first day. In three sunny days, the water temperature may rise by 7 to 10 degrees.

The efficiency of a solar blanket, however, relies on a few factors. 

These factors include the cover thickness, exterior temperature if the pool is outdoors, interior temperature if the pool is indoors, the amount of direct sunlight, and if you’re pairing the solar cover with a pool heater.

What Are the Types of Solar Pool Covers?

1. Solar Blankets

Solar Blankets, also known as bubble covers that have a layer of bubbles trapped within a sheet of durable plastic material. 

This unique design serves a dual purpose: enhancing heat retention and preventing evaporation.

The principle behind solar blankets is simple yet effective. The bubbles on the cover act as tiny solar collectors, absorbing sunlight and converting it into heat. 

This heat is then transferred to the pool water, gradually raising its temperature. 

The plastic material of the cover further traps the generated heat, preventing it from escaping into the surrounding air. 

This not only contributes to pool heating but also reduces heat loss during cooler nights.

Solar blankets come in various thicknesses, typically measured in mils. 

Thicker covers tend to provide better insulation and heat retention, ensuring more efficient pool heating. 

Your choice of thickness depends on factors such as climate, pool usage, and personal preferences.

In terms of installation, solar blankets are relatively easy to use. They are usually cut to fit the shape and size of the pool, ensuring optimal coverage.

2. Solar Rings

Solar Rings, also referred to as solar sun rings or pool solar discs that have a circular shape and a series of inflatable rings connected by a flexible material. 

Each solar ring is equipped with a layer of UV-resistant material that captures and absorbs sunlight. 

This absorbed energy is then transferred to the pool water beneath the rings, gradually raising its temperature.

The rings are connected with each other by the flexible material, forming a chain-like structure that can be spread across the pool’s surface. 

This interconnected design offers the advantage of modular coverage, allowing the rings to fit pools of various shapes and sizes.

However, they don’t offer full coverage like a traditional solar blanket might. 

While their design makes them adaptable and easy to handle, gaps between the rings can occur. 

These gaps might lead to a slight reduction in heating efficiency and a less effective barrier against water evaporation.

3. Liquid Solar Covers

Liquid Solar Covers represent an entirely different approach to pool heating and evaporation control. 

Instead of physical barriers like solar blankets or solar rings, this method involves adding a biodegradable liquid to the pool’s surface.

Once applied, the liquid forms an invisible monomolecular layer on the water’s surface. 

This thin layer serves as a barrier, reducing the rate of water evaporation. 

And since evaporation is a primary cause of heat loss in pools, by slowing it down, the liquid solar cover helps in maintaining the water temperature.

However, the effect of liquid solar covers in raising the pool’s temperature might be less than that of traditional solar blankets or rings. 

They’re mainly designed to maintain existing warmth rather than boosting the temperature. But in conjunction with a pool heater or other heating methods, they can contribute to energy efficiency by reducing the loss of generated heat.

Can a Solar Cover Be a Replacement For a Solar Pool Heater?

A solar cover can’t be a replacement for a solar heater, as these two pool accessories serve different primary functions and possess distinct capabilities.

A solar heater actively collects solar energy using solar panels, converting it into heat to substantially warm the pool water. 

Depending on the design, location, and weather conditions, solar heaters can significantly increase the water temperature, making swimming comfortable even in cooler seasons.

On the other hand, a solar cover, whether in the form of solar blankets, solar rings, or liquid solar covers, acts primarily as a barrier. 

Its main role is to minimize heat loss through evaporation and retain existing warmth. 

While it can absorb sunlight and provide some heating effect, this tends to be milder in comparison to a dedicated solar heater.


Do Solar Covers Really Heat the Pool?

Solar covers really heat the pool by absorbing sunlight and reducing evaporation, mainly effective for smaller pools with dark surfaces.

Does a Solar Blanket Heat the Pool During the Day?

A solar blanket heats the pool during the day by absorbing the sunlight that strikes its surface. The sun’s rays penetrate the blanket, transferring heat directly to the water underneath.

How Long Does It Take to Heat a Pool 10 Degrees?

It takes about 3 sunny days to heat a pool 10 degrees, depending on various elements such as the type of solar cover used, the size of the pool, and the initial water temperature.

What Is the Flow Rate of Solar Pool Heating?

The flow rate of solar pool heating is 2 gallons per minute, although this figure might vary depending on the specific design and capacity of the system.


As promised, we’ve answered the question of how fast a solar cover can heat your pool. 

We’ve also delved into various types of solar covers, such as solar blankets, rings, and liquid covers, explaining their functionality and effectiveness.

And if you ask for my advice, I’d recommend carefully considering the size and location of your pool, the climate in your area, and how often you plan to use the pool. 

These factors will help you select the perfect solar cover to meet your needs, whether you want to minimize heat loss, reduce evaporation, or slightly boost the water’s temperature.

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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