You rest but solar collector works. Hot water free of charge starting from April and till September in Latvian climate. With the help of 1 m2 sized solar collector you can heat 60 l of water a day. The temperature of heated water can be almost 50 C. In order to provide a family of 3-4 people with hot water you will need 3 m2 sized solar collector.
1 m2 sized solar collector in the period from April till September heats 10800 liters of water. 6 months x 30 = 180 days x 60 liters (average water volume) = 10 800 liters.
To heat such water volume with boiler you will need to use up till 500 kW/h of energy. The price for 1 kW/h is 0,075 LVL. Therefore you save up to 40.00 LVL by using only 1 m2 sized solar collector.