Water for domestic or space-heating use can be heated with the sun. Using either evacuated tubes or flat-plate collectors, liquid can be heated to over 180 degrees. This heat is then transferred to a tank or tanks to be used for the desired purpose. Typical efficiencies for solar collectors results in around 0.10 to 0.15 BTUs per square foot per hour. A typical 50-square-foot collector will generate about 80 gallons of hot water per day.
Another way of generating hot water with the sun is use a hybrid hot water heater that pulls the heat from the air using heat-pump technology. A solar PV system can provide power for one of these units, and the efficiency of the heater is up to three times higher than a standard electric hot water heater.