Home › Solar Cover Guide

Solar Cover Guide

What a solar cover does

Solar covers are sheets of plastic with air bubbles on one side. Placed bubble-side down on the water, they block evaporation, which is the largest heat loss for many pools. They trap a layer of air that slows heat loss and, depending on colour, let sunlight pass into the water. On sunny days the pool gains heat; overnight it keeps more of what it has. Heated pools see their heater run fewer hours; unheated pools can gain several degrees over a stretch of good weather.

Choosing thickness and colour

• Thickness: covers are sold in mil (thousandths of an inch). Thinner covers are lighter and cheaper; thicker ones last longer and resist UV damage but are heavier to handle.
• Colour: clear covers often let more sunlight through to warm the water; darker or tinted covers may hold heat differently and can reduce algae growth by blocking light. Some have a reflective side. Maker claims vary, so focus on durability and ease of use.
• Fit: measure carefully. Buy a size larger than the pool and trim to fit with scissors, leaving a small overlap.

Using a reel

Daily use is what makes a cover work. A reel on wheels or a fixed bracket lets one person roll the cover on and off in a minute or two. Without a reel, many covers end up in a pile beside the pool. If your pool shape makes reels awkward, cut the cover into sections that are easier to handle.

How much heat does it save?

A cover can cut heat loss sharply, especially at night. Government and industry guidance often cites heating energy savings of roughly half or more compared with leaving a heated pool uncovered, depending on climate and use. Our sizing calculators include a cover setting so you can see the effect; see also pool cover heat loss.

Safety

A solar cover is not a safety cover. Swimmers, children and pets can become trapped under it. Remove it completely before anyone enters the pool; never let anyone walk or play on it; keep the reel and stored cover away from the edge so children cannot climb onto it into the water. Pool fence and gate rules still apply.

Chemistry with a cover

Less sunlight on the water slows chlorine loss, and less evaporation means fewer mineral changes. You may use less sanitizer. Remove the cover during and after shock treatments as the chemical label directs, and let the pool breathe. Do not leave the cover on during high chlorine levels if the product label warns against it, since some chemicals degrade cover plastic.

Care and lifespan

Rinse the cover with plain water occasionally, store it out of direct sun when off the pool, and avoid leaving it bunched in the sun. UV and chlorine slowly make the plastic brittle; when it starts to flake or tear, replace it, because a flaking cover sheds plastic bits into the pool and protects less. Lifespans of a few seasons are common.

Worked example

Figures below are illustrative examples (2026-10-29), not quotes or guarantees.

Assumptions: a 450 sq ft pool kept at 82°F with average night air at 62°F, light wind. Uncovered holding need ≈ 450 × 20 × 12 = 108,000 BTU/h. With a solar cover for 12 night hours cutting loss by an assumed half, the pool saves about 54,000 × 12 ≈ 648,000 BTU per night, about 19.4 million BTU over 30 nights, or roughly 231 therms of gas input at 84% efficiency.

Solar covers on unheated pools

Without a heater, a cover helps the pool keep the sun's daily gain. In sunny climates the result can be several degrees warmer than an uncovered pool, extending the season. The gain is weather-dependent and slower than any heater.

Alternatives and add-ons

Thermal foam covers hold more heat but are heavier. Automatic covers are easiest to use daily but cost much more and require professional installation. Liquid covers help a little but are no substitute. Wind breaks complement any cover. Compare options in pool cover heat loss and plan heater size with the pool heater size calculator.

Fitting tips

Lay the new cover on the water bubble-side down and let it sit in the sun for a day so it relaxes and flattens. Then trim along the waterline with sharp scissors, leaving a few inches extra for shrinkage over time. Around steps and ladders, cut carefully and keep offcuts for small gaps. Mark the end that attaches to the reel so it goes on the same way each time.

Storage when not in use

When the cover is off for a pool party or a long swim, roll it onto the reel and shade the reel with a cover made for it, or store the cover in a shaded spot. Heat trapped in a tight roll in direct sun can warp the plastic. At season end, clean, dry and store it flat or loosely rolled away from rodents.

Solar cover or solar rings?

Solar rings are separate floating discs that cover part of the surface. They are easier to handle than a single sheet but leave gaps, so they block less evaporation. They can make sense for oddly shaped pools or for owners who cannot manage a reel. Covering most of the surface is what counts.

FAQ

Which side faces down?

The bubble side goes down, against the water.

Should I leave it on all day?

If no one is swimming, yes; it limits evaporation while still letting sun in.

Can I use it with a salt system?

Yes, but check the maker's chemistry guidance and remove it during superchlorination.

Try the calculator · Back to FAQ & guides