Mortgage rates vary from lender to lender because lenders have different appetites for risk and different overhead costs. When a lender reaches its capacity of loan applications its employees can process, it might keep rates slightly higher than necessary; when business is slow, the lender might charge slightly lower rates to drum up business. Because lenders' mortgage rates vary, it's smart to shop for a mortgage from several lenders because you could save thousands of dollars over the life of the loan.