there are closing costs, and escrow costs, less so if you stay with your bank. If you change banks then the cost goes up.
the real question is will you save at least 2pts on the interest? if not then the extra cost is not worth the hassle.
i went from 6.5 to 4.25% my monthly went down about 200$ but my savings over the course of the loan is about 200,000$ i had to kick in about 20K to cover changing banks and setting up a new escrow and refilling my TAX escrow.
if your trying to save 1pt or less its not worth it. you would be better off making extra payments and try to shorten the loan instead.
you need a amortization calculator.
then you can try and figure out the savings.
^ try this one
I'm not sure about the correct formula but there are tons of them online that can show you a spreadsheet of the payments