Instant light with the lift of a weight!

Generating 20 minutes of light from a descending bag of rocks.

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GravityLight is the first, award-winning solution by Deciwatt - inspiring the world by creating light with a bag of rocks.

For the 1.1 billion people without access to electricity, GravityLight was designed as a clean, safe and affordable alternative to kerosene lamps.

GravityLight is a unique solution:


Instant light


No sun or batteries needed

The descending bag powers an alternator giving you light

Simply hang, fill the bag with rocks and ?lift? to light?

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Multi-light system


Designed to replace kerosene lamps



With additional SatLights you can spread the light further


Our Tech and Specs


GravityLight is a lamp that is designed to hang from suitable fixtures in a house or dwelling. It uses a bag that can be filled with heavy items and winched up. As the bag descends it drives a generator through a gearbox which provides direct electrical power for a single LED. Additional SatLight lamps can be connected to the main GravityLight unit to extend lighting. Multiple Satlights can be linked together (recommended max of 4).

Contents Quantity
GravityLight GL02 1
SatLight 2
Power cable 2
Zip tie 1
Paper Bag 14
GL02 weight (empty bag) 1.2 kg / 2.6 lbs
GL02HS Boxed weight 1.75 kg / 3.85 lbs
GL02HS Box dimensions 280 x 223 x 153 mm
Master carton dimensions (4 boxes) 455 x 310 x 280 mm
Max loaded bag weight 12.5 kg / 27.5 lbs
Nominal Voltage* 2.7 V DC
Max current* 0.031 A
Max electrical power* 0.085 W
Luminous flux 15 lm
Luminous efficiency 208 lm/W
Colour temperature 5000 K
Colour Rendering Index > 70
Beam angle 147°
IP rating IP2X

Inside the Tech/ A Closer Look



How to Set Up GravityLight

A Revolutionary Idea

When the Therefore design consultancy team were appraoched by SolarAid in 2009 they were challenged to create a low-cost soalr light to reach off grid families living on less than $3 a day.  The aim of this challenge?  Create a sustainable alternative to kerosene lamps. 

Designers Martin Riddiford and Jim Reeves took on the challenge. After realising that batteries and photovoltaic (PV) panels were two thirds of the cost, they decided to look beyond solar and battery-powered devices.

This led to the invention of GravityLight – the first of its kind.


GravityLight doesn't need batteries or sunlight and costs nothing to run. It takes seconds to lift the weight that powers GravityLight, creating 20 minutes of light on its descent.