Efficient lighting is needed for sustainable architecture. A 13 watt LED lamp emits 450 to 650 lumens. which is equivalent to a standard 40 watt incandescent bulb. A standard 40 W incandescent bulb has an expected lifespan of 1,000 hours while an 3W chip LED grow light can continue to operate with reduced efficiency for more than 50,000 hours, 50 times longer than the incandescent bulb.
One kilowatt-hour of electricity will cause 1.34 pounds (610 g) of CO2 emission. Assuming the average light bulb is on for 10 hours a day, one 40-watt incandescent bulb will cause 196 pounds (89 kg) of CO2 emission per year. The 13-watt LED equivalent will only cause 63 pounds (29 kg) of CO2 over the same time span. A building’s carbon footprint from lighting can be reduced by 68% by exchanging all incandescent bulbs for new LEDs in warm climates. In cold climates, the energy saving may be lower, since more heating is needed to compensate for the lower temperature.
LED light bulbs could be a cost-effective option for lighting a home or office space because of their very long lifetimes. Consumer use of LEDs as a replacement for conventional lighting system is currently hampered by the high cost and low efficiency of available products. 2009 DOE testing results showed an average efficacy of 35 lm/W, below that of typical CFLs, and as low as 9 lm/W, worse than standard incandescents. The high initial cost of the commercial LED bulb is due to the expensive sapphire substrate which is key to the production process. The sapphire apparatus must be coupled with a mirror-like collector to reflect light that would otherwise be wasted.