GravityLight is a gravity-powered lamp designed by Deciwatt for use in developing or third-world nations as a replacement for kerosene lamps. It uses a bag filled with rocks or earth, attached to a cord, which slowly descends similar to the weight drive in a cuckoo clock. This action powers the light for up to thirty minutes. With neither batteries nor need for the sun, the lamp provides light instantly, can be stored indefinitely and used in many different environments.
There are currently two models of GravityLight supported by Deciwatt, the GL01 and GL02.
SDG 7: Affordable and Clean Energy
Market Suggested Retail Price
Target Users (Target Impact Group)
Household, Public Sector Agencies, NGOs
Distributors / Implementing Organizations
Deciwatt and Gravity Light Kenya Ltd
Mass produced in Kenya
Intellectural Property Type
User Provision Model
The lamp is distributed through local distribution networks, partners and sales agents (door-to-door networks, farmer groups, and more traditional market stalls). International distribution is handled by various international partners listed on the GravityLight webpage.
Distributions to Date Status
Distribution started in December 2016, with about 140 products being made each day in Kenya. Within 3 years of launch they plan to have sold 450,000 GravityLights.
Specifications for the GL01 and GL02 models:
A toll-free support line via SMS or over the phone Deciwatt also provide an support webpage, with links to installation guides, instruction manuals and other relevant documentation.
Lifecycle: GL01 model: 3 months - 1 year of continuous use GL02 model: >3 years of continuous use The GL02 also comes with a 1 year warranty.
Manufacturer Specified Performance Parameters
Pull the cord for instant light One lift creates 20 minutes of light Totally weather independentNo battery or external power required GL02 has 50% greater efficiency than and 12 times the lifespan of the GL01.
The product is designed to pay for itself within 3 months, saving families an average of 70 USD per annum.
Vetted Performance Status
Testing performed by the manufacturer found that the GL02 has a lifecycle of >3 years of continuous use on their testing rig, however no third-party testing has been performed.
The GL02 instruction manual includes the following safety advice, due to the heavy weight of the bag: GravityLight suspends the bag from a pulley, which reduces the strain on the cord and the gearing. This device complies with part 15 of the FCC Rules in not producing harmful interference.
Complementary Technical Systems
Possibility to add additional SatLights (connected light points) which can be daisy- chained around the room and used as task lights.
Academic Research and References
Anonymous, 2013, Gravity Light. Appropriate Technology, 40(4), pp. 60-61.
Sahota, J., 2017, GravityLight. Alternatives Journal, 43(2), pp.12-12.
Yakubu, Y.F., 2017, GravityLight in Nigeria. Energy Planning and Analysis Department, Energy Commission of Nigeria.
Support. n.d. Deciwatt global.
Deciwatt Ltd. 2014. GravityLight – GL01 Specifications. Deciwatt.global. Deciwatt.
Deciwatt Ltd. n.d. GravityLight – GL02 Specifications. Deciwatt.global. Deciwatt.
Deciwatt Ltd. n.d. GL02 Inventors Pack. Deciwatt.global. Deciwatt.
Deciwatt Ltd. n.d. GL02 Instruction Manual. Deciwatt.global. Deciwatt.
Deciwatt Ltd. 2017. GL02 Declaration of Conformity. Deciwatt.global. Deciwatt.
Hossen, Md. Shahed, Md. Tazul Islam, and Sabir Hossain. 2015. Design and Fabrication of a Gravity Powered Light. In International Conference on Mechanical Engineering and Renewable Energy 2015 (ICMERE 2015). Chittagong, Bangladesh: ICMERE 2015.
Compliance with regulations
Deciwatt's Declaration of Conformity for the GravityLight highlights all of the regulations it complies with in various jurisdictions. These include: CE, General Product Safety Directive 2001/95/EC, EMC Directive 2014/30/EU, IEC/EN/BS 55015, IEC/EN/BS 61547, IEC/EN/BS 61000-3-2, IEC/EN/BS 61000-3-3, IEC/EN/BS 62493, IEC/EN/BS 62471, RoHS Directive 2011/65/EU, WEEE Directive 2012/19/EU, IEC/EN/BS 60598-1, IEC/EN/BS 60598-2-4, FCC Part 15
GravityLight is tested in the Deciwatt workshop and out in the field. The GL02 Inventors’ Pack describes some aspects of the testing process, including their custom built Accelerated Life Testing rig. In 2014, it was tested in 1000 households across 26 countries to assess functionality and ease of use
GravityLight was called one of The 25 Best Inventions of the Year 2013 by Time Magazine. Operating the GravityLight: 1. The user fills the bag with 12kg of heavy objects such as rocks or sand 2. The weight is lifted by pulling down on a bead cord. On release, the weight falls very slowly, transforming potential energy into kinetic energy as it powers a drive sprocket, which rotates very slowly with high torque 3. A polymer gear train running through the product turns this input into a high speed, low torque output that drives a DC generator at thousands of rotations per minute 4. It generates just under a tenth of a watt, to power an onboard LED and ancillary devices. GravityLight has a DC jack where auxiliary lights (SatLights) and other devices, such as a radio, can be attached 5. Once the weighted bag reaches the floor, which depends on how high it was installed, it is simply lifted to repeat the process A pulley system is included, so users of any height or strength can lift the bag right up to the top - giving the maximum drop time. The 2 SatLights as additional light points connected to the main unit are included with the GravityLight. 
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