Active solar hot water systems use solar panels with tubes of water to harness heat from the sun and provide hot water for homes. The water in the tubes is heated as it passes through the panels and is then supplied to where hot water is needed, like for showers or washing dishes. While not completely emissions-free, solar hot water provides around 70% renewable energy. It is most commonly used in China but can work in any climate as the panels can still absorb some solar energy even on cloudy days.