Entrepreneur Elon Musk facing a battle for German hearts and homes
If Elon Musk's vision of millions of households producing all their own power becomes a reality, it will probably happen first in Germany.
But he will face a battle for market share against local firms with years of experience in renewable energy.
The South African-born entrepreneur's company, Tesla, best known for its electric cars, sparked global interest in the idea of self-powered homes in April, when it said it would start selling lithium-ion batteries for households next year.
The batteries, called Powerwalls, connect to solar panels on the roof of a house and aim to store enough power during the day to drive kettles and washing machines at night.
They raise the prospect that households one day will be able to rely fully on clean energy and become independent of the grid.
There are big challenges.
The technology does not yet allow most users to disconnect from the grid - the German solar industry association BSW estimates that batteries currently raise solar power self-sufficiency to at least 60pc.
Buying and installing solar panels and batteries costs around €10,000 or more. But the technology is improving and costs are falling, and some analysts think Germany - with more solar panels than anywhere in the world and sky-high power prices - could become the industry's first mass market.
"The business model of power batteries is becoming increasingly attractive," said Norbert Schwieters of PwC, noting market estimates that sales in Germany could reach half-a-million within a decade, up from around 25,000 now.
If the market does take off, Musk will have a fight on his hands against German companies with established retail networks and years of experience managing solar equipment.
"Tesla has made sure that they're seen as a lifestyle gadget," said Volker Wachenfeld, in charge of hybrid energy and storage solutions at SMA Solar.
It is one of a number of German companies with ambitions in the market, including Sonnenbatterie and Varta. Daimler Accumotive is also due to launch a product, while Solarwatt, owned by major BMW shareholder Stefan Quandt, says it is ready to join the fray.
Tesla, ready for a fight, has struck partnerships with German companies Beegy and LichtBlick in order to benefit from local expertise. (Reuters)