Applying for a mortgage online is convenient - you'll probably save a lot of time by filling out the application sitting at your home computer instead of at the loan officer's desk.

But can you save money?To find out, we logged on to three popular online mortgage sites and shopped for a $200,000 mortgage for the purchase of a hypothetical $250,000 home in the Northeastern United States. Our fictional buyers had enough cash to make a 20 percent down payment, plenty of income and the top credit ratings necessary to qualify for the best rates.

We tried to beat the average rate-point combination for the Northeast that week - 7.09 percent with 1.3 points - as reported by Freddie Mac, which resells mortgages as bonds. You're not likely to beat the average rates online (not by much, anyway) unless you do a lot of pointing and clicking.

We found the best deal through mortgage broker HomeShark (www.homeshark.com): a 7.125 percent rate from Flagstar Bank of Bloomfield Hills, Mich. That was higher than the average rate, but closing costs were lower - a 0.75-percentage-point refund (or $1,500 on a $200,000 loan), which would cut closing costs to $1,208.

QuickenMortgage (mortgage.quicken.com) had the same rate, offered by Chase Mortgage. But even with a $225 rebate of closing costs for applying online, the mortgage carried 1.75 points, or $3,225 with the rebate.

You can't beat the averages without knowing what they are. Start by getting a weekly update from Freddie Mac on the Internet, at (www.freddiemac.com). Then, comparison shop online. If you find the best rate there, go for it.

But don't neglect to check rates close to home. You can't recognize a great deal from an online lender until you've shopped your local market, says Keith Gumbinger, vice-president of HSH Associates, a Butler, N.J., company that surveys lenders. You can search current rates in 120 markets for free at (www.kiplinger.com) (click on "Yields & Rates").

Online or off, check all the rate-point combinations. Each Web site we checked showed a half-dozen or more. Ask about rates for the very best borrowers. The loans are harder to qualify for but could trim your costs or interest rate considerably.