Indoor light levels are much lower than outdoor light levels. Low levels of light may affect your energy level.
Light and darkness at the appropriate times of day are essential parts of a healthy life. The natural light-dark cycle offers a regular 24-hour rhythm with high levels of light during the day and darkness during the night. In modern society we use artificial light sources to prolong our day, or lighten up the night. During daytime, most people live indoors and are not exposed to natural light levels.
Natural outdoor light levels range from around 2000 lux on a cloudy day up to at least 100 000 lux on a bright sunny day. Indoor light levels in an office are much lower. At the level of the eye, in the direction of gaze, indoor office light levels range between 100 and 500 lux. At home in the evening, warm white light levels hardly ever exceed 100 lux. These intensities have probably no effect on increasing your energy level.
Low, indoor light levels may decrease our level of alertness, both during the day and during the night. Most people recognize this as it is sometimes difficult to stay awake in a dark lecture room, even during daytime.
Low light levels during the evening and night are favourable in inducing sleep. Increasing indoor environmental light intensity during the day could be a remedy to fight low levels of alertness. Light levels of 1000 lux and 5000 lux have been shown to be effective in increasing alertness during daytime. By increasing the blue part of the spectrum in the light source, also lower light intensities might be effective.