Home water heaters are typically the second-largest user of energy out of all home appliances. Converting an electric water heater to solar will be good for your budget and good for the environment. Heating water with the sun is an ancient practice, but integrating it into a home water system can be daunting. With preparation, research and patience, the work should go smoothly and your new hot water system will be up and running.
Determine if your water heater has a second spout on the top or not. If it does, that will be the new hot water input. If it does not, you'll need to buy a water heater conversion component and attach it to the cold input line at the bottom of the heater.
Install the solar water heater on your roof, or other space with good sun. There are several types of solar water heaters available, and you will need to determine which works best for your circumstances. Batch heaters are the least complicated, but can present problems in climates with freezing weather. Flat plate collectors are the most common, and can easily be adapted to any climate. Evacuated-tube collectors are the most efficient, and the most expensive, and are typically only used in multi-unit buildings and for industrial applications.
Connect the solar heater to the water heater. Do this by rerouting the cold supply, through a pump, to the input on the lower side of the solar heater, and then connecting the hot water output from the top of the solar heater to the new input on the water heater. The pump must be controlled by a differential sensor, which will trigger the pump based on temperature differences in the system.
Install temperature and pressure relief valves at the top of the solar heater and the output of the water heater. The output from the old heater will remain the same spout. If you have freezing temperatures in your area, you will need to fill the solar heater with antifreeze, and connect it to a heat exchanger. In that case, route the water supply through the heat exchanger, and not through the solar water heater. The rest of the system will remain the same.