Harsha sent me an urgent email this morning. He said, “It might be true that sun can give 5 units/m2/day. But because the efficiency of solar panels is only 15% and there are losses in the system, we only produce 0.30 to 0.6 units/m2/day. For example a battery based system will give you 3 units of energy per 8 m2 of panels ( 1.1 KW). while grid-tie system can give you around 4 units of energy per 8 m2 of panels, as there are no battery and inverter losses in a grid tie system.” It reminds me of a story, where a man asked Siva for a pot of water, when all he could hold was a cup and all he could drink was a gulp. So though the sun can give us about 5 units per m2/day in Bangalore, we can safely only expect 3 units/8 m2 for a standalone system. So if we wish to generate 20 units per day, we need, again simplistically speaking, seven 8 m2 panels. If we don’t have that much space or budget, we would have to use energy efficient devices and use a bit of current from the grid.