In Denmark, if you have a fixed-rate mortgage, you are always allowed to buy back the bonds at their nominal value. For that reason, you absolutely can save money by refinancing when the the interest rates go down (you still have to pay some fixed fees in order to do so). The funny thing is, that you can sometimes also save money when the interest rate goes up, because in that case you can buy back the underlying bonds at less than their nominal value. The savings in this case come in the form of tax savings, because you can deduct the (higher) interest.