What’s the difference between a solar heater and a “solar” cover? That’s like asking what the difference between a swimming pool and a hole in the ground.
A solar pool heating system circulates pool water through solar collectors (or panels), transferring the sun’s warmth into your pool. A solar cover, while great at keeping heat in, does not actually generate warmth in your pool (a swimming pool loses up to 70% of its heat through evaporation – a cover acts as a lid, trapping the heat).
Most pool owners have, at one time or another, tried one of the popular bubble-type “solar” covers on their swimming pool, hoping to take the chill off. Other more recent entries into the solar cover industry include circular plastic discs, or solar rings. Unfortunately, some newer entries have tried to claim heating capabilities upwards of 20,000 BTUS per disc. In the end, no solar cover will ever heat a pool like a solar pool heater will.
That being said, while a cover may not heat a pool, it will definitely help keep that heat in. For that reason, it is always a smart idea to utilize some sort of cover on your pool.