Dixons, Comet and Argos have promised to inform customers in stores that they can buy extended warranties elsewhere if they want to.
The Office of Fair Trading has obtained legal undertakings from the retailers after it found that customers weren't getting value for money in this £1bn market.
Stores will have to offer leaflets showing that warranties are available elsewhere, maintain a price comparison site so buyers can shop around and provide clearer information about annual costs.
They'll also have to conduct regular independent mystery shopping exercises to help ensure shoppers get accurate information from sales staff.
The OFT proposed these tighter measures in February.