Small energy supplier Ovo has today launched an app, which enables its prepay customers to top up their energy without leaving their homes.

Prepayment meters are electricity and gas meters that let you pay for your energy on a pay-as-you-go basis. You top up via a key or card, which you can credit at newsagents, post offices, garages, or sometimes online. See our Prepaid Energy guide for more on this.

But Ovo, which currently offers the cheapest prepay tariff on the market for the average dual fuel user, has today launched a service that enables its prepay customers to top up by text, online or via its new app. It will also alert customers when their credit is running low.

Ovo says it's the first provider to launch such an app. It adds that the idea behind the tool is so customers can see how much is being spent on energy bills day-to-day, which should help keep costs to a minimum.

Below we explain what the service is and how to use it.

What does the new service do?

Ovo's new service enables customers with its PAYG+ app to top up via the app rather than having to go to the shops to top up via a key or card. It also enables users to top up online and by text.

Both the app and online service also show how long your current balance is expected to last based on your previous usage, while you can also set up a text or email alert to notify you when credit is running low.

The app and online service also enable you to schedule regular top ups and you can set up for your account to be topped up automatically if your credit falls below a certain threshold.

What's the catch?

To benefit from Ovo's new service you'll need an Ovo smart meter. This is being offered to all new prepay customers, for free. Ovo says its existing prepay customers can request a smart meter for free, and it adds that it's pro-actively contacting customers to offer them too.

Once the smart meter has been installed, Ovo will collect data from it and display it on the app and online.

Is the service free?

The app is available on Android and iOS and can be downloaded and used for free. It's also free to use the online service, and to text the top up service.

Is it worth switching to Ovo for?

According to Citizens Advice there are around 11 million prepay customers in the UK but traditionally these households pay far more for their energy.

The cheapest prepay tariff for an average dual fuel user for example, is over £200/year more expensive than the cheapest non-prepay tariff. So it's generally not worth switching to prepay if you're not already on it.

If you are already a prepay customer, you can use our Cheap Energy Club to see if you could switch and save.

Ovo's online prepay tariff is currently the cheapest on the market for an average user, although it's a variable tariff meaning the price could change at any time. Ovo topped the tables in our last energy customer service poll, with 81% of its users scoring it great.