Solar water heaters reduce the fossil fuel that would be used to heat the water, reducing CO2 emissions very slightly, and therefore can be part of the climate change solution.
This is perfectly true, but as you say a small effect. Even in countries like Cyprus and Israel where nearly every home has a solar water heater and the climate is very conductive it saves something like 1-3% of electricity consumption I recall?
I meant it's not a solution in the class of solar panels, where the electricity can be used for nearly anything. Also heater tech isn't very high tech and didn't need much gov support in developing it. Mandating it in law where climate allows may have been useful though.
