Hi Susie! Short answer: 5-1/2 years. I was doing a commute of about 85 miles round trip and the original 2011 LEAF had a nominal 100-mile range battery. I was able to do my 85-mile round-trip commute on just my overnight charge for about 5 years. Then I had to stop for some top-off on my way home every day, or sometimes I could top off at work. That's when I decided to spring for a new battery, even if it was going to cost $8,000. The new LEAF I leased (and eventually owned) had a nominal 150 mile battery, so that was the big enticement. The kicker is, just about that time I started working from home and never needed to do that commute again. So I could have just kept going on the old battery till today and longer. Oh well, it has come in handy when I had to go into the office or drive somewhere far every now and then.