“It takes a lot of energy to heat water. Typically, up to 30% of a home’s energy consumption is used just to heat water for bathing, laundry, and cleaning. By installing a solar hot water system, homeowners can shave 200 to 500 kilowatt-hours off their electric bill per month, saving money and reducing pollution. Installing a solar hot water system is typically the first and most cost-effective step when turning to the sun for energy. Even if a photovoltaic system is your primary interest, a solar (thermal) hot water system along with a PV system will provide the best economics and space-efficiency on your roof.”
More at Solair Systems
Solaire solar assisted air conditioner
Image source: Made in China.com
I’m seeing some real nice small units on the market, both water heaters and air conditioners. Most seem too big and expensive for small homes.
Wiki Solar Air Conditioning
Solar power growth chart