People performing an energy comparison to find cheaper tariffs could have benefited from a scheme by Scottish Power to ensure its customers are on the best deals.
The energy supplier has helped more than 20,000 customers make savings by performing targeted tariff checks highlighting cheaper gas and electricity payment options.
This is one of the company's main commitments to improving its customer service and involves writing to users with a personalised quote showing how they can save money.
Around 21,700 people responded to the letters, resulting in estimated total savings of over £4 million.
Chief executive of Scottish Power Neil Clitheroe said: "We are pleased that so many customers have been able to reduce their bills by making simple changes to the way they pay for their energy."
Recently, Scottish Power also announced it will be trialling a new advice scheme to offer users tips on how to cut their energy bills.
Make sure you're not paying too much for your energy - compare gas and electricity prices now at energyhelpline.com or call 0800 074 0745