Series I or Series EE?

I have $15,000 sitting in a bank as a CD not even making 1.5 percent interest. If I was to transfer it all into Saving Bonds, which series would give me the most interest after taxes? I don't need it now and probably will let it sit for the next 15 years or longer. I plan to retire in 10 years. Tom's response If you moved your $15,000 into either Series EE or Series I Savings Bonds, you'd earn a higher rate and you'd pay no tax at all until you redeemed them. You could hold them as long as 30 years before redemption, so you should be paying a lower tax rate by then (but tax rates could change several times between now and then, so it's difficult to say for sure). Experts disagree on whether Series EE or Series I will have the better long-term return. I think Series I has a slight edge. You can read why here: What's Best - Series I or EE or Marketable Treasury Securities.