Solar panels or photovoltaic cell technology has come a long way in the last seven decades to produce enough electricity to power a home in the second decade of the 21st-century. One of the most complex and often confusing areas of solar power in recent times has been the plethora of options available for heating water in any home. The traditional hot water heater can be powered by the sun or combined with a solar thermal hot water system, or with a tankless system. 

One of the most important aspects of heating water with solar power is the fact the sun can be harnessed to provide a constant stream of hot water in recent years. As the solar power panels used throughout the world have improved in efficiency and power produced, the ability to heat water has developed. Although the production of power using solar energy dates back to the end of the 19th-century, mass-production of panels did not begin until the 1950s. The early pioneers of PV panel production created a limited amount of energy rated at just 20 watts, which would not have provided enough power to heat water for a residential household. 

In the 21st-century, the average PV panel array produces a higher level of energy, rated at just over five watts with an efficiency percentage of 18. Improvements made in the development of hot water heaters see the latest storage tank style heaters operating at an average of 3.6kW which should be covered by a single up to date solar panel. One solar panel would be enough to power a traditional storage hot water heater throughout a day as this is the most inefficient appliance used in most homes. 

A second option to explore is the use of a dedicated solar thermal hot water heating system coupled with a heat pump to make the most cost-effective option on the market. Those areas of the world which have a large amount of sunlight each day are often those where the solar water heating system is of most use and provide a high-quality option for heating water simply and efficiently. Tankless water heaters are a difficult option to discuss as the level of energy used is often difficult to determine and would normally require a combination of solar and traditional energy. Making sure plenty of panels are available to cover the burst of energy needed to heat water at a rate of over three kilowatts is required. A solar panel owner should monitor their use of electricity linked to their hot water system to ensure enough power is produced to cover that used by the heating element.