A pool's temperature is dependent on numerous factors, including air temp, wind and amount of sunlight. So if you drop this in your pool and see the water temperature increase over the next few days, it's hard to know how much is due to this product, and how much is due to favorable weather. For a valid test, you'd need two identical pools, put the Solarpill in one, and compare the difference over the next few days. Since I don't have two pools, I tried the next best thing... I filled two 20 gallon plastic tubs with pool water (so they'd have the same concentration of chlorine, etc). Then I put some (too much) of the Solarpill juice in only one. I measured the temperature over the next few days and did see that the Solarpill tub was consistently 1 or 2 degrees Fahrenheit warmer (the difference varied as overall daytime/nighttime temperatures changed). However, for this test I had intentionally put way too much Solarpill juice in that tub, so the concentration was way higher than you get when used properly in a full-size pool (per directions, up to 30,000 gallons). In fact, the concentration was so high in the tub that it became cloudy in spots after settling overnight. (I've never observed any cloudiness with the lower concentrations it achieves in a pool.) My next test was to use a concentration closer to that of the pool (the pool had gotten the full Solarpill treatment a few days earlier). So I dumped out the Solarpill tub and then refilled it with pool water. Now this step is tricky and error-prone because the chemical floats on the surface, so the goal is to fill the tub while capturing the right amount of surface water (chemicals) and not letting the surface (chemicals) drain out as you remove it from the pool. I did this as carefully as I could and again measured the temperatures between the two tubs over the next few days. This time I saw no measurable difference between the temperature of the two tubs. CONCLUSION: The concentration affects the effectiveness. At recommended concentrations, you might see a slight increase, but I suspect it won't be more than a degree or so. So by using this product, there should be some savings in water bills (due to reduced evaporation) and in heating costs, but it's hard to calculate if that savings outweighs the cost of the Solarpill. Note: this was clearly not a pure scientific test for several reasons, including: No good method to measure/approximate concentration. The tubs contain much less water than a pool, so amount of day/night temperature variation is much larger. The tub walls are a very different material than pool walls (may affect how much the sun warms them), and the walls are surrounded by air, not dirt (affects heat loss through walls). Perhaps most importantly, the tubs are much shallower than the pool, however their surface-area to depth ratio is far less (thus the evaporation effects that the Solarpill relies on may be less). If I were to do this experiment again, I'd find two containers that are very wide and shallow to mimic more closely the surface-area to depth ratio of a pool.
