A third of homeowners focus on the interest rate being offered when remortgaging without looking at the overall cost of the loan, a survey showed.
Magazine Which? Money warned people looking to switch home loan to make sure they look at the total cost of the deal and not simply focus on the headline rate.
It said this could be misleading as the average mortgage arrangement fee is now £1,104.
A survey for the group found 26% of homeowners admitted that they selected their current mortgage based on the interest rate charged, with just 20% looking at the overall cost of the deal.
Nearly a third of people admitted they had never switched mortgage lender, while 30% said they were on their lenders' standard variable rate, which is traditionally an uncompetitive option that people are automatically put on when a fixed rate or tracker deal comes to an end.
Martyn Hocking, editor of Which? Money, said: "The cost of mortgages has soared in the last couple of years, but a lot of the focus has been on what's happening with interest rates when in fact it's the total cost of the deal that's important.
"Arrangement fees are now more than £1,000 on average, and sometimes much higher, which means that an eye-catching interest rate can be misleading.
"Whatever you do, don't take the lazy option of simply taking out a deal with your bank or staying on your lender's standard variable rate. If you shop around and do your homework, you could cut your mortgage costs by hundreds of pounds."
