In the old days you could get any kind of solar blanket you wanted, as long as it was blue, 12 mil. Now solar covers come in Clear and Black colors, and in 8 mil, 12 mil or 16 mil thickness.
If that's not enough choice for you, solar blankets are now sold side by side with Solar Rings and Solar Squares, and also available is Liquid Solar Blanket, an evaporation and heat loss chemical that forms a micro-thin layer on the surface.
So, what's best? An entire solar cover, or smaller individual squares, or one of the many liquid solar chemicals? Let's take them one at a time.
Solar Covers or Solar Blankets
In 1974, a young executive working for the Sealed Air corporation, maker of films and bubble wrap, put their air cell packing on his home pool, and found that it heated the pool and helped keep the heat in during cool nights. Today, you just order by pool size. For inground pools of custom shape, you would order a rectangle size that fits over the entire pool, and then cut the blanket to fit inside and hug the tile line around the pool.
PROS: Available in 3 thicknesses, or 3 lifespans really, to fit any solar blanket budget. All thicknesses will heat the pool at the same rate. A solar blanket's biggest advantage is that it covers the most surface area, which both heats the water more and controls heat loss better. They are also relatively affordable and when used with a reel and protected from the elements, can last 3-7 years, depending on the thickness.
CONS: That you need to use a solar reel mechanism, in most cases (with exception to small pools). And on some larger pools, removing and replacing the solar blanket can be kind of a hassle, or something that requires two people.
Solar Rings or Solar Squares
In 2004, a California housewife took her pool service guy husband's idea for a unique solar pool cover, and ran with it. With family investment, prototypes floated on her Murrieta home pool. With proof of product, the business grew each year until it was being sold in thousands of retail outlets, to pool owners everywhere. The Solar Sun Ring uses an inflatable outer ring with magnets surrounding a thick vinyl center.
PROS: Easy to install and easy to remove. Magnets hold Solar Sun Rings or Solar Squares together, but you can easily pull them apart and stack them on the deck (in a shady area). No solar reel or solar roller is needed! Long lasting and easily storable for winter, these 5' diameter rings are easier to use than traditional solar blankets.
CONS: The price for a complete set of Solar Sun Rings or Solar Squares may be more expensive than regular solar blankets. The inflatable outer chamber, which keeps these afloat, could become punctured, requiring repair. A recent study shows that full solar blankets are the most effective method.
Liquid Solar Cover Chemicals
In 1998, a college PE teacher applied for and received a patent for his unique HeatSavr® and began marketing Solar Fish, which contained a month's worth of the evaporation suppressant. Liquid evaporation control chemicals are not new, in fact they have been used for over 100 years as a way to control water reservoir levels, especially during times of drought. Now there are at least half a dozen brands of 'Liquid Solar'.
PROS: So. Easy. To. Use. Easier than reading that sentence anyway. Just pour Liquid Solar Blanket right amount in the pool, and it covers the surface with a microscopically thin layer that blocks heat from escaping. Invisible, tasteless and non-toxic, you'll never know it's there, but you'll notice the difference in heat retention.
CONS: Not nearly as effective as the other types of solar covers above. The Cal Poly study, and other studies done on similar chemicals place the evaporation loss effectiveness at about 20-40% of a complete solid cover. And, it won't add heat to the pool, only helps retain heat or prevents heat loss.
Like Walter Cronkite would say "And that's the way it is ...", that's the complete line of covers designed to reduce evaporative heat loss, retain heat, and in the case of 2 out of 3 types, add 5-15 degrees to your pool.
SPP Pool Expert