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A huge growing market will be batteries in homes. Germany is trying to push it to go from 30% of photovoltaic self-consumption up to 70% (when the sun shines, people usually are away at work). The excessive electricity is sold to the network.
This requires between 5 and 10kWh storage capacity (compared to the 50+kWh of a Tesla) for a single family home. The current price is about 20€cts/kWh for the storage over the whole lifetime. So it is not economic yet, but it should be within a few years and I hope that Tesla will contribute to it. Solar costs about 15€cts/kWh and electricity from the network is around 25€cts/kWh. When solar will reach 10€cts and storage 10€cts/kWh, the market will be very important.