Customers in the UK are paying £2.7 billion too much for their broadband packages because they don't change providers often enough, according to uSwitch.
This equals an average £140 extra every year for each customer.
Recent research by uSwitch shows that 12 million customers have not changed their provider in the last year, while five million have never changed.
The average bill currently stands at £14.64 a month, but the comparison site says there are more competitive deals available - especially for new customers.
When choosing a new broadband package, 61% of customers said reliability of connection was the most important factor, with 57% choosing the speed of broadband, 54% opting for value for money and 11% saying customer support.
At the moment, there are six providers - Primus, TalkTalk, Sky, Plusnet, Orange and O2 - offering broadband deals for less than £10 per month.
Ernest Doku, spokesperson for uSwitch, says the broadband market has become extremely competitive, with a huge increase in low-cost packages - particularly those below £10 per month.
"If you are coming to the end of your contract, now is the time to take a look at your broadband.
"Consumers should also pay close attention to their broadband usage levels by checking their bills, then ensuring that they get a speed and download limit that suits their household's needs," he adds.