Louisa Pearson: What’s the connection between ferries in Hong Kong, illuminated maps of Leeds town centre and the calculator on my desk? They all run on solar power, that’s what.

So while some people are always whinging on about the sun not shining enough in Scotland to make solar power viable, I’ve been thinking that, surely, if we put zillions of solar panels in the world’s brightest places and string together a load of cables, we can all have access to cheaper, greener power.

It turns out an organisation called Desertec Foundation is doing just this. It has a very nice quote on its website from the founder, Dr Gerhard Knies: “Within six hours, deserts receive more energy from the sun than humankind consumes within a year.”  Where do I sign up to buy shares?

The Sahara-powering-the-world scenario is not quite as straightforward as I’m implying – for example, one problem with solar farms in deserts is that there’s so much dust the equipment requires cleaning on a daily basis. As deserts are not known for their lochs, more work is needed into waterless cleaning options. So the idea is hugely attractive and progress is being made, but the desert power plants aren’t quite there yet in terms of meeting all our energy needs.

I know you won’t believe me but I have just received a phone call from a man offering me free solar panels for my roof. Sometimes I wonder if my life is a secret reality TV show. Somewhere out there an editor is saying, “Quick, call her about solar power and see how she reacts.” How she reacts is to say, “How can you afford to give the panels to  me for free when the feed-in tariff has been reduced from 43p per kilowatt hour to 21p and will soon be reduced further?” “Er, I will get my manager to call you back,” says the man. The manager does not call back.

This nuisance call has, however, provided  a seamless link into a discussion about the generation of domestic solar power. I can’t be the only one who has spotted loads of panels appearing in recent months. The householders have probably all gone for these free ones in return for 25-year rental agreements on their roofs.

According to Which? research, you could save over £10,000 in the long run by paying for the panels yourself, but this assumes you have the money to pay for the installation. Catches to the free scheme? Things to think about include the fee you’ll pay if you move house before the term is up; whether new buyers would be happy to take on the lease agreement when you sell; and what the small print is in terms of roof repairs and whatnot.

If you go for a free panel scheme, the installation company gets the feed-in tariff for the energy you generate. Install your own and the rate you’ll get currently stands at 21p/kWh but will reduce to 16p/kWh next month. The Energy Saving Trust (www.energysavingtrust.org) has a good overview of the situation with tariffs. It also lets you calculate your home’s solar-generating potential online. I am proud to announce that I could generate half of my electricity needs via solar panels, saving me the grand total of £289 over 25 years.

So if you’re doing it to save money rather than the planet, you might be disappointed. But if you want to power more than a calculator with the sun’s rays, to cut your carbon footprint, the technology is willing and able.