Solar energy can contribute up to 80% of all the energy needed for domestic hot water (showers, faucets, etc.). This is very interesting, even from the finantial perspective. The payback is in few years and you also receive I.R.S. benefits (up to 803€ in Portugal - 2010). 

From the technical view, domestic hot water solutions can be categorized as: 

• Thermosifon System - the tank is integrated in the solar panel forming a single unit. It uses natural convection to avoid the use of any water pumping device.
• Active Solar Hot Water System - although solar panels are placed outside, the tink is placed indoor. There is a pump and a controller to circulate the water.

Key Factores to take into account

The main factores to take into account when purchasing a solar hot water system are the following:

• The correct system syzing according to the consumption patterns and solar collectors orientation. Choose installers with know-how!
• Solar collectors (and other components) should be certificated (Solar Keymark) and must come with 6 years warranty (minimum).
• In order to have your solar system considered for the energy certificate of your house, it's mandatory to firm a maintenance contract (for 6 years) with the installer company.