All of which have some sort of collector up on the roof. This is where new technology comes in. Earliest collectors were merely big metal tanks painted black. That worked to some extent, but these days, the technology is far more advanced. The typical collector looks like a flat panel and is about 10′ by 4′ for about 40 sq ft. Sounds big, but remember, this is up on a roof. The depth is only about 3′, so the panel is quite unobtrusive. The panel itself is manufactured to grab every bit of sunlight that comes its way and convert it into heat.
When the sun is shining and the water flows through the copper tubing in the collector, it gets hot. This hot water then flows down into a tank and from the tank to the various hot water needs in the house or business. Of course, there are times in every climate when the sun is not shining (heavy overcast, rain) For those times, there is a back-up element in the tank, so hot water is always available.