Around 3.5 million households could see their electricity and gas supplies moved from SSE to Ovo, following plans announced by the Big Six supplier to sell its household energy business to its smaller rival.
The takeover is expected to be completed late this year or early next year.
Ovo is the biggest independent energy firm, with 1.5 million customers. Acquiring SSE's customers will make it the second-biggest, after British Gas.
Currently Ovo is one of the top-10 firms in our annual energy companies satisfaction survey. SSE doesn't score as highly, however.
has agreed to buy 's household energy and related services business. This includes customers for gas and electricity, telecoms (including broadband) and other home services. This also includes customers from SSE's other energy brands, including Atlantic, Scottish Hydro, Southern Electric and Swalec.
With the deal only announced today, it's too early to know how it will work in practice for SSE customers.
But SSE said that, should the deal go through, it will do 'all it can to ensure a smooth transition for customers'.
It added that the SSE brand will continue to exist for a period after the takeover, operated by Ovo, to allow the companies to transfer customers smoothly and maintain good customer service.
Ovo was placed 6th out of 30 companies in our most recent , with five stars for its online customer service. In contrast, SSE finished 22nd. So new customers might hope to see improved service with a new supplier.
Plus Ovo says new customers will also benefit from the latest technology, including online account functionality which tells you which appliances are using most electricity in your home. And Ovo has developed a vehicle-to-grid charger and EV smart charger.
Earlier this year SSE said that it planned to sell or float its energy services arm by mid-2020.
SSE is losing customers; in the last year more than half a million households switched away from it.
SSE has debts and some of the funds from the sale will be used to reduce them.
Not necessarily. SSE currently has the cheaper deal on sale of the two companies. For a medium user of gas and electricity, it would cost £1,138 per year on average, compared with Ovo's cheapest deal which costs £1,154 per year. However Ovo's deal has a fixed price for two years, while SSE's is one year.
But neither company offers the cheapest deals on the market. SSE's cheapest deal is £292 a year more expensive than the cheapest deal available.
Approval from regulators (the Financial Conduct Authority and Competition and Markets Authority) is needed before Ovo can complete its purchase of SSE's energy business.
Prices are based on a dual-fuel tariff available in all regions in England, Scotland and Wales paying by monthly direct debit, with paperless bills.
Energy use is based on Ofgem's annual average figures for a medium user (12,000kWh gas and 3,100kWh electricity per year).
Data is from Energylinx. Price given are averages across regions, rounded to the nearest whole pound and correct on 13 September 2019.