Who could be more different than Germans and Californians? The Teutons are supposedly uptight and bureaucracy-obsessed, while the American West Coasters are infamously laid-back and libertine. Yet it was these two that transformed solar energy into a zero-carbon power source that today decorates rooftops the world over.

Solar energy’s coming out is a thrilling tale, which the American science journalist Bob Johnstone tells with verve and authority in Switching to Solar, now available on Kindle.

Johnstone’s story flits back and forth across the Atlantic, but begins in 1970s America where some of the key breakthroughs were made in photovoltaics.

In their initial tilt at solar, the Americans made a series of mistakes. Firstly, the common wisdom was that solar power would one day be produced by huge power stations.

Secondly, it was the utility companies, not the giant oil companies, who were solar’s real enemies. “They understood,” he writes, “what remains the case today: every kilowatt produced outside their gates is a kilowatt they’ll never sell.”

Lastly, the Americans were clueless about getting around the exorbitant price of the earliest solar panels.

Meanwhile, in West Germany a powerful environmental movement had risen up, although the Germans were slower than the Americans in picking up on the potential of the sun and wind.

It was innovations in policy, Johnstone argues, that kick-started Germany’s energy revolution and, principally, the feed-in tariff.

Johnstone calls the tariff an “ecological masterpiece”, a law that requires utilities to buy clean energy from individual producers, for example, from farmers in the Black Forest with a wind turbine in a field. Importantly, the utilities must buy it – all of it, at all times – at a rate above the going market price.

Johnstone chronicles the evolution of the tariff. One concerned citizen was Wolf von Fabeck, who, in the 1990s, launched a drive to force local utilities to connect private people experimenting with solar energy to the grid and to buy electricity from them.

This was the first step towards decentralising Germany’s power supply. “The idea was that private owners of solar systems should be treated as if they were utilities,” explains von Fabeck.

The feed-in tariff catapulted Germany to the forefront of global production in alternative energies. By last year, a thriving renewable energy sector in Germany employed 450,000 people.

Back in California, an Austrian called Arnold Schwarzenegger had been elected governor. He had an eye on what was happening in Germany and even brought over European experts to advise him with the result that in 2008 and 2009 California, too, endorsed feed-in tariffs and the state’s residents now generate over half the total solar power in the entire US.

Still, this boom has to be put in perspective. Solar power accounts for just 0.25 per cent of California’s total energy capacity. In Germany the figure is closer to three per cent.

But the road is wide open. In just three or four years’ time, say experts, the price of solar-generated electricity will have dropped so much that the feed-in tariff will be abolished, a victim of its own success.