Has anyone used an air heater that works well?

I installed a solar water heater before, it doesn't work well, we have a lot of rainy days here. The electric heater is not energy efficient at all.

Last year I installed a 1 HP 150 liter tank, which is from Zhongshan Nopo. Only three thousand. It worked well in the winter this spring. But if you have a large family, four to five people, it is best to buy their 1.5 horsepower with 200 liters of water tank, only four thousand. Its home brand to six or seven thousand dollars it, now the manufacturers really black, bragging about what energy-saving to cheat our money, take us as a stupid X.