Last week's announcement by serial entrepreneur 's car companyto launch a home battery that charges on solar power , is in many ways a step that could result in a large scale uptake of a sustainable source of energy. ET explains what the Powerwall is how this could be a game changer.The Tesla Powerwall is a big home battery made of lithiumion and charges on solar energy . The batteries come in two variants, costing $3500 and $3,000, and are capable of storing 10 kwh and 7 kwh of energy respectively. To put this in perspective, a 1-kilowatt heater can run for ten hours with 10kWh of energy. These batteries are housed in a well-designed package and you can hang them on a wall. It's about 4 feet by 7 feet and has a width of about 7 inches. The price, is also a third of such batteries available in the market.The batteries are primed for home use, where typically more electricity is consumed during peak hours in the morning and evening. By storing the electricity generated during the day, the peak hour demand can be met with ease. Tesla has also announced a scalable Powerpack which it intends to sell to power utilities and corporations.Solar power works if panels and batteries are affordable. Cost of panels are already falling, thanks largely to China. If battery prices are also on the way down, one can expect a lot of action in the domain. India has an ambitious solar energy plan, which will generate huge orders that will lead to economies of scale, helping solar energy reach ‘grid parity' or the point where it costs the same as thermal power.If successful, the battery will be a game changer in India's standby power sector, which burns diesel. Diesel generators add up to an estimated 60,000 mw, or the combined capacity of 15 ultra mega power plants. These are essential for malls, telecom towers, hospitals etc because a power cut can cripple operations. For residential areas, reliable low-cost storage can help consumers get off the grid, as is already happening in some Western countries. In far-flung areas, such batteries will support setting up of microgrids in hamlets. In hilly areas, where one needs light more than fans, such technology, along with use of energy-efficient LED bulbs can power homes at a small cost.