They couldn’t have been any clearer. If you are worried about climate change, you’ve got to do your bit and reduce your harmful emissions. For some, this will involve switching to an electric car and giving up red meat. For everyone else, there is no excuse not to switch to a green electricity (and in some cases, gas) supplier.

And there’s a double incentive to go green – not only does it send the message to the traditional energy firms they have to up their renewable game – it will also, most likely, save money through lower bills.

A British Gas customer, in an average UK home – on the firm’s standard variable tariff – spends about £1,200 a year heating and lighting their home. If they live in a bigger house, or have teenage children, bills will be somewhere in the £1,600- to £2,000-a-year range.

We have 12 years to limit climate change catastrophe, warns UN Read more

By switching to Guardian pick Pure Planet – an independent supplier that offers electricity from 100% renewable sources (no nuclear, either) and “100% carbon offset gas” – that same “average” customer can reduce their bill to about £920 a year, a saving in excess of £250.

Pure Planet is one of new entrants to the energy market, but, unlike some others, this has a big firm behind it – BP has a stake.

There are two big caveats. Customers have to manage their account via a smartphone app which will not appeal to everyone. Also, the tariff is not fixed, meaning prices could well go up – other suppliers have recently been raising prices. Pure Planet gets good customer reviews on Trustpilot, and Money has not received any complaints.

Scrapping UK grants for hybrid cars 'astounding', says industry Read more

Pure Planet’s Steven Day says prices across the whole market will likely rise over the next few months, but points out that the new breed of green suppliers will remain among the cheapest suppliers. “Green power is now cheaper than brown and there’s no reason for anyone not to do the right thing and switch over,” he says.

If you prefer a supplier you can call – or one that is marginally cheaper – Edinburgh-based People’s Energy offers 100% green electricity but only conventional gas. This will cost the average customer about £900 a year – a £300 saving over British Gas’s standard customer. Again, prices could go up over the coming months.

Yorkshire Energy has the cheapest fixed tariff – Green Turtle – fixed until 30 November 2019 at just under £1,000 a year for average gas and electricity usage.

Switching supplier is easy and takes about 10 minutes. Dig out a recent bill and do a search using a comparison site such as Energyhelpline.com. Make sure you click on “all plans” to ensure you are shown green deals as well as the suppliers the comparison site may be promoting.