For renewable energy consultant Adarsh Vansey, creating a clean energy system in his own home was a no-brainer. When he designed and built his 2, 500 square feet independent house in south Bangalore's JP Nagar in 2006, he was clear that his home, which he shares with his parents, would be run largely on electricity generated through solar panels and a wind turbine.

Vansey specialises in wind energy and has helped clients across India set up solar-plus-wind systems that reduce dependence on grid power. Unlike most homeowners who opt for the more popular solarpowered stand-alone systems, Vansey opted for a dual system (with solar and a micro wind-energy system) to fully utilise the favourable windspeed his rooftop is exposed to, to generate power during the night. He installed imported 640-watt solar panels (he clarifies that the number of panels have nothing to do with the quantum of energy generated as long as the total surface area remains the same;it is more scientific to refer to the optimal power generation from the panels) and a 650-watt wind turbine made by a Punebased company called Unitron. The total set-up cost around Rs 3. 5 to 4 lakh at the time. "The costs have reduced considerably now because solar panels have become cheaper, from Rs 220 per watt (when I installed these) to Rs 60-75 per watt now, " Vansey explains.

In the Vansey home, the energy generated using the dual units is about 4-5 kilowatthours (kWh) of power every day (one kWh is what we commonly refer to as one 'unit' of power). This is enough to run CFL and LED lights, fans, the TV, washing machine, microwave and refrigerator. The family's hot water needs are taken care of by a solar water heater - a feature that has become increasingly common on the city's rooftops in the past few years.

Part of the solar and wind generating systems are a set of batteries and an inverter. "Solar photovoltaic cells work on the principle of converting light energy to electric energy, " explains Vansey. "This energy is generated in DC (direct current) mode. The wind turbine is simpler;it converts wind energy to electric energy, again in DC mode. This current charges the batteries, which stores it for future use. The current from the batteries is supplied to the house via the inverter. " The household usually has back-up power for two days and is 85 per cent off the grid. Electricity bills are "in the lower hundreds".

So why don't more people adopt this inexhaustible source? Vansey shrugs: "Maybe people are deterred by the high initial costs, but if you're spending upwards of Rs 50 lakh on a house, setting up a renewable energy system isn't even 10 per cent of that. And potentially, you could run a whole city on this!"