David Cameron’s got one. So should I have one too? No, I’m not referring to a chauffeur-driven car to carry my briefcase. I mean a wind turbine, of course. Or even a solar panel.

You can now walk into a B&Q store and walk out with a wind turbine. And both B&Q and Currys sell solar panels for homes.

This is not strictly speaking personal finance. But what I want to know is, disregarding all the green arguments, does it make sense to invest in this new technology? In other words, if you’ve got some cash burning a hole in your pocket, would you get a better return from investing in a wind turbine or solar panel than you would by putting your money in a savings account?

Certainly some of the green energy solutions being marketed to homeowners look pretty cheap. B&Q sells wind turbines for under £1,500 and solar panels start at a similar amount. Currys sells a more upmarket solar solution, starting at around £9,000. The question is: how much energy do these solutions produce and what sort of dent will they make in your annual energy bills.

I’m not sure about a wind turbine. But I certainly wouldn’t mind having some solar panels on my roof. What would convince me to get one, however, is the level of returns I would get from installing a system. If the yield was, say, 5 per cent or more, I’d be heading off to B&Q this weekend.

But even if the yield was a little less I’d still consider it. If the annual savings on my electricity bill equate to 3 per cent of the costs of installing the solar panels, for example, this would equate to a gross yield for a higher rate taxpayer of 5 per cent. And remember this yield should be pegged to energy prices. So, over time, this yield could rise healthily, quite possibly outpacing broader retail price inflation.

So, in order to probe the figures, I decided to home in on the Currys solar panel scheme. The entry-level solution costs £9,000 with the top-of-the-range system, designed for particularly large houses, costing £25,000. In both cases, government grants are available which can cut this cost in half.

Currys is working with Sharp, a leading manufacturer of solar cells. It says most people buying panels are getting the full 50 per cent reduction on the cost of panels, thereby cutting the cost of its biggest system to £12,500.

Anyway, here comes the maths, although bear in mind that there are numerous variables in making such calculations – from the amount of sun and the level of government grants to the size of the solar panels being installed (bigger systems are more cost-effective and should therefore give a better yield).

The most expensive Currys system should provide about 4,000 kilowatt hours a year, according to Sharp, possibly more if you live in a sunny area and less if you live in the north of Scotland (the Energy Saving Trust reckons the average three-bedroom house consumes 3,300 kilowatt hours a year).

The Currys’ scheme uses photovoltaic panels which produce electricity. So, if the sun is shining, and your TV, kettle and other electric appliances are turned off, the chances are that you will be generating more electricity than you need. This excess is sold back to the National Grid. Different energy suppliers will pay different amounts, but you should expect to get somewhere between 8p to 10p per kilowatt hour. So, in our example, you might shave £360 off your electricity bill. That equates to a net yield on the £12,500 installation costs of a shade under 2.9 per cent (or a gross yield of almost 5 per cent). Not bad when you think that this yield should rise annually in line with energy prices. The main downside is that your solar panel will have a limited life, even if this is a pretty long one. Sharp guarantees the performance of its panels for 25 years but says it has plenty of solar panels that have been working healthily for more than 40 years.

So the nearest comparison for this investment has to be an annuity for a 40-year-old (someone with a life expectancy of 40 years or so) rising in line with inflation. There aren’t too many people buying these, but according to William Burrows annuities, the annuity rate for a single 40-year-old male rising in line with retail price inflation is just under 2.3 per cent.

On this basis, there certainly appear to be compelling reasons to consider solar panels. These should become greater if solar technology falls in price and energy prices continue to rise.

rob.budden@ft.com