Using electricity 24 hours per day, something most of us take for granted, raises a household’s expenses by approximately 40 percent. In a country where the average income ranges from minimum wage to less than $1 a day, this added expense isn’t seen as crucial.

However, there’s an incredibly simple solution that’s both greener and safer.

The Solar Bottle Bulb was originally developed by students at MIT and spearheaded by Mac Diaz, the innovative founder of MyShelter Foundation. It uses plastic water bottles and a little bleach to bring light to the darkness.

To create the bulb, developers fit 1.5 liter plastic bottles containing water and bleach snugly into holes in a metal roof. Sunlight refracts through and off the water, creating free solar lighting equivalent to 55 or 60 watts of clean white light. The bleach inside the bottles prevents algae from forming inside them. The bottles don’t heat up, and are designed to produce clear light for approximately five years.