MoneyExpert.com says one million people whose three-year fixed rate deals are due to expire will be moved to average standard APRs of over 6.5%.
Average fixed-rate mortgages in 2003 had APRs of 4.22%, owing largely to a low Bank of England base rate of 3.5%.
But as interest rates have increased, lenders have raised the APRs customers receive once their fixed-rate deals run out.
That means borrowers who either bought a house or remortgaged on three-year deals in 2003 will risk paying large SVRs. Homeowners paying 4.22% on a 100,000 mortgage on a repayment basis in 2003 would have faced monthly payments of around 545. If they move to a 6.55% rate now their payments will rise to 725 a month. That is an extra 180 a month, or 2,160 a year.
Around 39% of mortgages taken out in 2003 were in fixed-rate deals amounting to 1,059,000 loans. Popularity of fixed-rates is high, with 1.3 million deals struck last year.
Sean Gardner, chief executive of MoneyExpert.com, says: Homeowners who were smart enough to fix their rates in 2003 cant take their good fortune for granted. Interest rates are rising and standard mortgage rates are too.
The mortgage market is different from three years ago, but thats not to say that there arent great deals to be had. Homeowners can keep a low rate if they do a bit of homework and review the market.