You can find net present value calculators on the web that will make this calculation for you. It's the same as a pension lump sum vs annuity calculator. The calculator will require the annuity value, an assumed interest rate and an estimate of your lifespan. The calculator will give you the net present value of the income stream. I just used on to help me figure out my net worth, as I will have a defined benefit pension annuity starting next year and was curious about its current value. Here's one, but there are many .
http://www.money-zine.com/Calculator...ty-Calculator/