The website says the price of an average standalone broadband connection has tumbled 36% in four years to £17 a month, with a maximum speed of 8Mbps.
Nearly 15 million households are now spending a total of more than £3bn a year subscribing to a service.
USwitch says the cheapest standalone broadband service is offered by Plusnet, at £10 a month for 8Mbps.
But nearly five million homes are paying more than £20 a month for their broadband, wasting £162m a year, says the site.
Orange is among those suppliers charging £20 a month for an 8mbps service.
Virgin Media plans to roll out a 50Mbps service by the end of 2008.