Solar radiation reaches a unit of space near the Earth’s orbit at a rate of 1,366 W/m² (Watt per square metre), as measured upon a surface normal (at a right angle) to the Sun. This number is the "solar constant". Of this energy, about 19% is absorbed by the atmosphere, and clouds reflect a further 35% of the total solar energy. Therefore solar energy received a sea level is much less. Its peak power is generally accepted to be 1,020 W/m².