Liter of Light
Open-source bottle bulb refracts sunlight for daytime interior lighting.
Wikipedia / Wikimedia Commons
Liter of Light is an open-source, low-cost daylighting device designed for homes with thin roofs. It works like a deck prism, using a clear two-liter plastic bottle filled with water and a small amount of bleach—to prevent algae—to refract sunlight indoors. Installed through a hole in the roof, it provides illumination equivalent to a 40–60 watt incandescent bulb during the day, offering a cheaper alternative to electric lighting. A properly installed bottle can last up to five years.
The concept originated with Brazilian inventor Alfredo Moser, who repurposed plastic bottles for indoor lighting. The idea was later launched as a social enterprise in the Philippines by Illac Diaz and the My Shelter Foundation in April 2011. Diaz adopted a local entrepreneur model, training community members to assemble and install the bottle bulbs for income. Within months, the project grew from a single carpenter in San Pedro, Laguna, to 15,000 installations across twenty Philippine cities. This success sparked similar efforts globally. The foundation also established a training center for youth, businesses, and volunteers. Within the first year, over 200,000 bottle bulbs were installed worldwide. In 2014, the initiative set a goal of lighting one million homes by the end of 2015. In January 2015, Liter of Light won the Zayed Future Energy Prize in the Non-Profit Organization category, presented to Illac Diaz at the Abu Dhabi Sustainability Week. It was also selected as one of 120 Global Innovators for the EXPOLive Impact Innovation Grant at EXPO 2020 in Dubai.
The Solar Bottle Bulb is installed through a roof to refract sunlight indoors. The innovation relies on inexpensive, durable, widely available materials to provide natural lighting, offering a cost-effective, environmentally sustainable alternative to daytime electric lighting, especially for low-income urban populations. The most common bottles are 1.5-liter plastic containers, filled with water and a small amount of bleach. The bottle is inserted through a hole in a corrugated metal roof and secured with a steel sheet to prevent slipping, with sealant applied around the hole for weatherproofing. The water’s refractive properties diffuse sunlight, producing omnidirectional light equivalent to a 40–60 watt incandescent bulb, depending on solar insolation. Installation instructions and material lists are publicly ava
- founder
- Alfredo Moser (inventor); Illac Diaz (social enterprise founder)
- field
- Open-source daylighting technology
- known_for
- Solar Bottle Bulb providing daytime interior lighting
- first_introduced
- Philippines, April 2011
- global_reach
- Over 200,000 bottle bulbs installed within first year
- award
- Zayed Future Energy Prize (Non-Profit Organization category, January 2015)
Lore & Background
Plastic bottles repurposed to provide indoor daylight lighting were first developed by Alfredo Moser of Brazil. The concept was introduced as a social enterprise in the Philippines by Illac Diaz through the My Shelter Foundation in April 2011. To promote sustainable development, Diaz implemented a local entrepreneur business model, enabling community members to assemble and install the bottle bulbs and earn income. Within months, the My Shelter Foundation expanded from a single carpenter in San Pedro, Laguna, to installing 15,000 solar bottle bulbs in twenty cities throughout the Philippines. This success inspired similar initiatives globally. The foundation also created a training center offering workshops for youth, businesses, and volunteers interested in building solar bottle bulbs in their communities. Within the first year, over 200,000 bottle bulbs were installed worldwide. In 2014, Liter of Light set a goal to illuminate 1 million homes by the end of 2015.
Reader's Guide
Liter of Light represents a low-cost, open-source approach to daylighting that addresses energy poverty in off-grid and low-income communities. The technology uses widely available materials—plastic bottles, water, bleach, and sealant—to create a durable light source lasting up to five years. Its significance lies in its simplicity and scalability: the design can be replicated locally with minimal training, and the social enterprise model empowers community members as installers. The initiative has spread to numerous countries, including Argentina, Bangladesh, Brazil, Chile, China, Colombia, Dominican Republic, Egypt, France, and India, each adapting the design to local conditions. In Brazil, the project expanded to nighttime street lighting in 2015. In Bangladesh, a local version called 'Botol Bati' costs approximately $2 to $2.50 USD. The project received the Zayed Future Energy Prize in 2015 and was selected as one of 120 Global Innovators for the EXPOLive Impact Innovation Grant program at EXPO 2020 in Dubai. Its legacy includes demonstrating how open-source design and local entrepreneurship can address both environmental and social challenges.
Did You Know?
- The device delivers about as much light as a 40–60 watt incandescent bulb.
- A properly installed solar bottle can last up to 5 years.
- The inventor, Alfredo Moser, employed polyester resin to secure the bottles.
- In Bangladesh, the local version called 'Botol Bati' costs approximately $2 to $2.50 USD.
Frequently Asked Questions
Who invented Liter of Light?
Brazilian inventor Alfredo Moser originally conceived the idea of turning a plastic water bottle into an indoor light source. The concept was later expanded into a broader social enterprise under the leadership of Illac Diaz.
How does Liter of Light actually illuminate a room?
A two-liter bottle filled with water and a small amount of bleach is mounted through a hole in a thin roof, and the water acts as a lens that bends and scatters sunlight into the interior space. During daylight hours the effect is roughly comparable to a 40-to-60-watt incandescent bulb.
Where and when did Liter of Light first go public?
The bottle-bulb approach was first deployed in the Philippines in April 2011. Within its first year of rollout, more than 200,000 units had been installed in homes around the world.
What major recognition has Liter of Light received?
In January 2015 the project was honored with the Zayed Future Energy Prize in the Non-Profit Organization category. The award underscored its impact as an accessible, low-cost alternative to grid electricity for daytime lighting.
How long does a properly installed Liter of Light last?
When set up correctly, a single bottle installation can continue providing usable daylight for up to five years. The small amount of bleach added to the water helps keep algae from forming and clouding the light over time.
More in Brazilian inventions 1-24
Spotted an error? Know more?
This is a living reference — every entry is fact-audited, and reader corrections feed straight into our audit queue. Suggest an edit · See this site's audit record