I bought one in the early 2000's, should be getting about 10% on it. The trouble with these is that the fixed rate has been 0% for some time now. If inflation does go down you could end up with a very low yielding bond. I forget what exactly it equates to on a yearly interest basis but series E bonds don't really pay squat until they hit the 20 year mark, at which time they are guaranteed to double. I wish when I was younger I had put the max into those each year I was able to, that's a nice little "pension" when you are older.
FYI, normal TIPS have the fixed rate well below zero (which makes the total yield add up to close to where the fixed rates bonds trade at, around 1-2%). These retail instruments are kind of no brainers if their fixed rate is artificially not allowed to drop below zero.
E bonds are guaranteed to double in value at 20 years, for a nominal (not inflation adjusted) ~3.5% return. They yield almost nothing before the 20 year term.
