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Sun provides heat - Use the heat in to heat hot water which can be used for any use




Winter is cold – summer is hot.

Sunlit area is hot – shaded area is cold.

Sunshine part of the building is hot, shaded part is cold.  

The only difference is the amount  / intensity of sun light the place gets.

When I was growing up in Nepal – forty years a ago, our school had a water heater on the roof top – it was enough for all the 100 odd students to take hot shower ! those days it was just a simple box with cold water pipes running around – not a big technology then.  The system is still working perfectly and no major work has been done on the system in the last 40 years !

Technology has advanced – hence the heating has been more sophisticated – meaning efficiency has increased.

If we were to have the roof top of every house with hot water system on the top at design stage, then that water will be enough to for cooking at showers as well even washing in most of the housing in the world ! It is free- not energy is needed again, it is one time investment only for the piping.   

Category of the action

Urban adaptation

What actions do you propose?


Mandate that every house / building should have hot water system installed   

Who will take these actions?


Government / municipality : should enforce the law

Architects should incorporate that in the design

Building / House owners should pay the initial cost  and enjoy free hot water for the rest of their life 

Where will these actions be taken?


Every where, all around the world ….

What are other key benefits?


Industries can use this water which will left the temperature from around 20 degree to around 60 degree – if needed this “hot” water can be heat treated to produce steam. 

What are the proposal’s costs?

none...just needs lobbying - and a rulling from local governement 

Time line

We estimate that currently 80% home in Kathmandu has hot water system. If the same can be duplicated in the world over next 10 years = imaging how much energy can be saved !  

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