British Gas is giving away 30 plug-in solar kits as the technology goes on sale in Britain for the first time.The energy supplier has launched a competition offering households the chance to win a plug-in solar system worth around £500, while confirming that it also plans to launch its own plug-in solar products.Plug-in solar became legal to buy and use across Great Britain on 27 August, allowing households to connect compliant systems with an output of up to 800W directly to a suitable socket.The government estimates that a system could provide up to 20 per cent of an average home’s electricity use and save households as much as £110 a year.Unlike conventional rooftop solar, plug-in systems do not require scaffolding or a traditional solar installation and can be positioned in suitable outdoor spaces such as gardens and patios, making the technology potentially accessible to more renters and households without a suitable roof.Read more: First look at the best plug-in solar panels as UK rules changeGet a free quote for solar panels for your homeBritish Gas commercial director John Evans said: “For a long time, generating your own solar power has meant having the right roof, the right home and the ability to make a significant investment upfront. Plug-in solar is now opening up another option for households who want to start generating their own electricity.”The supplier has also revealed plans to allow eligible British Gas customers to earn money from surplus electricity generated by plug-in solar and exported to the grid.British Gas says customers will be able to receive payments for eligible exports “in the next few weeks”, although it has not yet announced details such as the export rate or eligibility requirements.That could provide an additional benefit for households whose panels produce more electricity than they are using at the time. The main financial saving from plug-in solar comes from consuming the electricity directly and reducing the amount bought from the grid.British Gas says its own plug-in solar products are coming soon, but has not yet announced which systems it will sell or how much they will cost.Households can enter the giveaway by registering their interest in buying a plug-in solar kit from British Gas before 16 September. The company says the 30 winners will be selected and notified between 17 and 30 September.Read more: Plug-in vs installed solar panels