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Collect all your Energy and Water Need from your Roof



This project promote the harvesting of  both energy  and water need of the household from its own roof. Energy need is obtained by home solar power system generating energy from sunlight through solar panels placed on the roof and water need is obtained by collecting and storing the rain water that fall on the roof.

Fossil fuels are the leading cause of climate change. Approximately 82% of electricity in the Sri Lanka generated by burning fossil fuels (Sustainable Energy Authority) . Reducing the electricity we draw from the grid means reducing carbon emissions. Similarly Centralized water supply schemes require energy, land and many infrastructure facilities which have a demand on the earth’s natural resources. Pipe water supply is provided to 46% of the population is Sri Lanka (NWS&DB) . The rest of the population has to rely on other sources such as wells, rivers and lakes. Sri Lanka has been experiencing frequent droughts and flood over the last few years attributed to climate change. This will adversely affect the islands water resources, resulting in water scarcity to majority of Sri Lankans.   Therefore the simple solution in this case is to increase the retention of water that is received during the rainy periods to be used during the non-rainy periods. Rain water collected from 100 m2 roof in the dry zone of Sri Lanka which receives an average 1000 mm of rain will collect 90,000 liter per year, this is 246 liter per day. 

Net-metering allows an electricity customer to use renewable energy sources within his premises to generate electricity and utilise it within his premises, and to export it to the national grid if excess power is being generated, to be recovered when needed. Electricity distributors in Sri Lanka  offer net-metering to their customers. A roof area of 100 ft2 of 9 m2 and 4 solar panels are needed to generate 1 kW energy. 


What actions do you propose?

1. Promote the implementation of existing policy on rain water harvesting and Net metering with decision makers 

2. Advocate for offering of incentives such as reduction of taxation on solar and rain water harvesting products. 

3. Promote the concept with Business Companies such as solar and water tank providers to offer the concept as a package to households

4. Promote the concepts with professional groups such as architects, Engineers, builders, Green Building Council ect.  

5. Bankers and Financial Institutes 

6. Individual householder 

Who will take these actions?

1. Government bodies for Policy implementation and offer incentives: Ministry of Power and Energy, Ministry of Water Supply & City Planning, Ceylon Electricity Board, National Water Supply & Drainage Board, Sustainable energy Authority

2. Business companies to implementation, technical support  and promotion

3. Professional bodies for promotion and design

 4. Banks and Financial Institutions for offer of loans

5. Individual householders for adoption of technology 

Where will these actions be taken?

Any where in Sri Lanka and around the world 

How will these actions have a high impact in addressing climate change?

Project will lead to reduction of fossil fuel through use of solar energy fro electricity and energy needed to pump and distribute water. It is stated that generating electric power causes over a third of all green house gas emissions in the United States (source: Environmental Protection Agency). Thus by reducing energy for electricity and water distribution it will reduce emission of green house gases. 

It also help to prepare households for climate change. Since variation in rain fall is predicted due to climate change leading to frequent droughts and floods. Households will be prepared for drought situation by having water stored in their own premises. Also it has been studies that rain water harvesting can also reduce flooding in cites by preventing water going in the roads. 

What are other key benefits?

Consumers have the ability to significantly reduce, or eliminate their electricity bill

Net metering solar power systems do not have to store the electricity they generate, exporting excess electricity eliminates the need for batteries,

Since consumers with net-metering are generating the energy that they are using, they are effectively protected from future electricity rate increases.

Rain water harvesting reduce flooding and soil erosion

Rain water harvesting introduce water conservation at the household level and also reduce over extraction of ground water 


What are the proposal’s costs?

A roof area of 100 ft2 of 9 m2 and 4 solar panels are needed to generate 1 kW energy. The utility cost of the system is LKR 65,000 ( US$ 464), System cost of LKR 350,000 per kW ( US$ 2500).  

The cost of 5000 liter rain water harvesting system is LKR 70,000 ( US$ 500). There is very little operation and maintenance cost for rain water harvesting system  

Time line

Short term: Policy implementation  offer, bank loans, promotion, adoption

Medium term: Adoption of concept by households

Long term Reduction of use of fossile fuel 


Related proposals

Rainwater harvesting is a technology used for collecting and storing rainwater from rooftops using simple techniques such as jars and pots


Sri Lanka Sustainable Energy Authority

National Water Supply & Drainage Board Sri Lanka 

Mr. D. A. Jayasinghearachchi (2008), Impacts of Climate Change on Water Resources and Adaptation Measures, Department of Meteorology Sri Lanka.

National policy on rain water harvesting in 2005