BBC Radio 4's Inside Money lets listeners explore the financial issues that matter to them.

Each week, presenter Lesley Curwen will offer her low-down on making the programme.

I've made lots of Inside Money programmes over the years about financial products which can confuse people and ultimately let consumers down.

We're talking about pensions, insurance and various types of complex investments.

But the subject of this week's programme was rather different, and I have to confess, it's one of the hardest we've ever had to unravel and explain.

Imagine trying to buy a virtual commodity, which is difficult to put a price on, where sales are unregulated.

Simon needed his steady sharp mind to cut through the maze of detail we encountered

The product in question is a carbon offset.

It's there to assuage your conscience, to counter-balance the effect of the carbon emissions you might generate from flying in a plane, driving your car or heating your home.

The listener who wanted to get a close look at carbon offsets was Simon Mallet, a technology consultant from Kent.

Visiting Simon's house is a lesson to those of us, like me, who are lazy about being green.

Simon showed me what he'd done to this former Victorian pub: he had installed giant tanks which act as water butts to collect rainwater for the garden.

There were huge solar panels on the roof, and his home is now registered as a power generator.

He seemed to be the ideal person to evaluate carbon offsetting for Inside Money.

Energy can be captured by solar panels to generate 'green' power

And it turned out Simon needed his steady sharp mind to cut through the maze of detail we encountered.

He had to weigh up several different systems which certify the projects (such as clean power plants) where his money might be going, to cut emissions in the developing world.

Different schemes work to different standards, and that means the price you pay can depend on which standard and which accreditation scheme you choose.

And even the best-known and most respectable standards have been subject to serious criticism.

I won't give away what Simon finally concluded about carbon offsetting.

You'll have to listen to the programme to find that out.

But take it from me - it made our brains fairly fizz and splutter, trying to understand how it works, and whether you can be sure about what your money actually buys.

In fact, I'm off for a much-needed lie-down.

BBC Radio 4's Inside Money: Carbon Confusion was broadcast on Saturday 4 August at 1204 BST and repeated on Monday 6 August at 1502 BST.

Lesley's Low-downs from other programmes this series