Buildings and Cities
LED Lighting (Household)
The origin of LEDs (light emitting diodes) dates back to the 1874 invention of the diode—a crystal semiconductor. Under certain conditions, diodes emit light. In 1994, three Japanese scientists invented high-brightness LED bulbs, for which they were awarded the Nobel Prize in Physics in 2014.
LEDs work like solar panels in reverse, converting electrons to photons instead of the other way around. They use 90 percent less energy than incandescent bulbs for the same amount of light, and half as much as compact fluorescents, without toxic mercury. By transferring most of their energy use into creating light—rather than heat, like older technologies—LEDs reduce electricity consumption and air-conditioning loads.
The price (per watt equivalent) for LEDs is two to three times higher than incandescents or floursescents, but falling rapidly. And an LED bulb will last much longer than either other type. Still, upfront cost remains an obstacle for household adoption.
When the sun sets, more than a billion people live in the dark. Low energy use means LEDs can be powered with small solar cells. Solar-LED lights can replace expensive kerosene lamps and their noxious fumes and emissions, while addressing the problem of light poverty.
diodes emit light…observed in 1907: Zheludev, Nikolay. “The Life and Times of the LED—a 100-year History.” Nature Photonics 1, no. 4: 189-192; Schubert, E. Fred. 2014. Light-emitting Diodes. Cambridge: Cambridge University Press, 2007.
1960s…commercial applications: Zheludev, Nikolay, “Life and Times”; Schubert, E. Fred. Light-emitting Diodes. Cambridge: Cambridge University Press, 2014.
Nobel Prize in Physics in 2014: Overbye, Dennis. “American and 2 Japanese Physicists Share Nobel for Work on LED Lights.” New York Times. October 7, 2014.
LED [vs.] incandescent [vs.] compact fluorescent: Pimputkar, Siddha, James S. Speck, Steven P. DenBaars, and Shuji Nakamura. “Prospects for LED Lighting.” Nature Photonics 3, no. 4 (2009): 180-182. 2009.
80 percent of…energy use [for] creating light: Pimputkar et al, “Prospects.”
kerosene lamps…emissions: Lam, Nicholas L., Yanju Chen, Cheryl Weyant, Chandra Venkataraman, Pankaj Sadavarte, Michael A. Johnson, Kirk R. Smith et al. “Household Light Makes Global Heat: High Black Carbon Emissions from Kerosene Wick Lamps.” Environmental Science & Technology 46, no. 24 (2012): 13531-13538; Meaker, Morgan. “The Developing World Faces a Silent Killer. Could a $1 Solar Light Help?” The Guardian. March 1, 2016.
“A sixth of humanity…[vs.] the electrified world”: Mills, Evan. “Can Technology Free Developing Countries from Light Poverty?” The Guardian. July 30, 2015.
India…1 million solar lighting systems: REN21. Renewables 2016 Global Status Report, Paris: REN21 Secretariat, 2016.
lighting…global electricity use: Neslen, Arthur. “Plan for 10 Billion Ultra-Efficient LEDs Lights Up Paris Climate Summit.” The Guardian, December 7, 2015.
LED Lighting (Household)
Project Drawdown defines LED lighting (household) as: the use of efficient light-emitting diodes (LEDs) in residential buildings. This solution replaces conventional residential lighting solutions.
Traditionally, there have been four types of lamps used in residential lighting: incandescent lamps, halogen lamps, compact fluorescent lamps, and linear fluorescent lamps. Globally, the incandescent and halogen lamps, which have the lowest luminous efficacy,  have been the most widely used. That trend is changing, however: in 2011, the market share of incandescent and halogen lamps was approximately 53 percent of global residential lighting, but in 2020, their market share is expected to decrease to 10 percent. There are good-quality LED lamps available at decent prices, but LEDs currently only capture 2 percent of the residential lighting market (DOE SSL Program, 2015; Bergesen et al, 2016). If the challenges in product quality are overcome, the prices reduced, and the luminous efficacy increased further, LED lighting is expected to take over the residential sector nearly entirely by 2050. The analysis below estimates the potential financial and emissions impacts of high adoption of LEDs in residential buildings, compared to conventional technologies.
The implementation unit in the analysis is lumen: a measure of the visible light emitted by a source, corresponding to the rate at which a lamp can produce visible light.  The functional unit is lumen-hour, which describes the production of visible light over time. Since the scope of this solution is residential lighting, only the lamps, not the entire luminaire (housing), were compared. The same luminaires in residential buildings can be equipped with different lamp technologies having the same cap type, facilitating easy replacement.
Total Addressable Market 
The total residential lighting demand was taken as the total addressable market for LED lighting (household): 30 petalumen-hours in 2014. This data was obtained from several sources, including the International Energy Agency (IEA).
Adoption Scenarios 
Impacts of increased adoption of LED lighting (household from 2020-2050 were generated based on three growth scenarios, which were assessed in comparison to a Reference Scenario where the solution’s market share was fixed at the current levels.
- Plausible Scenario: This scenario uses a linear growth curve of residential LED adoption from current adoption to 90 percent adoption of the residential lighting market in 2050.
- Drawdown Scenario: This scenario uses a linear growth to 95 percent adoption worldwide in 2050.
- Optimum Scenario: This scenario has linear growth to 100 percent by 2050.
Direct grid emissions (with typical emissions factors ), as well as indirect production emissions, were included in the climate calculations. The indirect emissions indicate that residential LED production releases slightly less greenhouse gas than the weighted conventional options.
First costs for LEDs average at US$19 per kilolumen,  which is compared to a weighted average of US$6.30 per kilolumen for incandescent lamps, halogen lamps, compact fluorescent lamps, and linear fluorescent lamps. Operating costs account for the residential price of electricity for powering average wattage installations, and amount to US$0.004 per kilolumen-hour for conventional lighting and US$0.0019 per kilolumen-hour for LEDs. No maintenance costs were included.
No integration effects were taken into account in this model, as no other Project Drawdown solution affected LED lighting (household).
LED technology was shown to avoid a significant amount of energy use and emissions in residential buildings. According to the Plausible Scenario, residential LEDs can reduce emissions by 7.8 gigatons of carbon dioxide-equivalent greenhouse gases, and can reduce operating costs by US$1.7 trillion over the period 2020-2050, while costing US$323 billion in first costs. This indicates that LEDs can be an excellent investment for any homeowner. Lower electricity prices and higher purchases prices (such as in countries where importation may be high) can diminish the financial value.
The Drawdown Scenario shows a potential emissions reduction of 8.2 gigatons, and the Optimum Scenario is ony slightly different, with an 8.7 gigaton avoidance.
The financial potential of LED lighting (household) should be key to its rapid adoption in the coming decades, leading to the emissions reduction potential being realized. The purchase price of LED products is still hampering the wider penetration of the technology, but the price is decreasing. LED lighting offers greater energy efficiency compared to conventional lighting technologies, but its adoption assumes that consumers are aware of and have access to it. To achieve this, educational campaigns can be run, and global distribution should increase as demand rises and prices fall.
The luminous efficacy of LEDs is increasing, making LED technology an increasingly attractive lighting solution in the future. LED lighting has other benefits not analyzed: it enables dimmable lighting, various colors of light, color tuning, and accurate directing of the light with reflectors and lenses.
 The amount of visible light produced for a given power supply.
 Adjusted units are presented in this summary according to the context: a kilolumen corresponds to a thousand lumens, and a petalumen corresponds to a million billion lumens.
 For more on the Total Addressable Market for the Buildings and Cities Sector, click the Sector Summary: Buildings and Cities link below.
 To learn more about Project Drawdown’s three growth scenarios, click the Scenarios link below. For information on Buildings and Cities Sector-specific scenarios, click the Sector Summary: Buildings and Cities link.
 From the Intergovernmental Panel on Climate Change (IPCC).
 All monetary values presented in US2014$.
 For more on Project Drawdown’s Buildings and Cities Sector integration model, click the Sector Summary: Buildings and Cities link below.
Full models and technical reports coming in late 2017.