What's tricky...hot water heaters are lined with glass. If for some reason, the glass liner has a hole or crack...it would be time to replace it. The trick though is that it's unlikely it's damaged like that unless you've been using it for a tackling dummy. Electric hw heaters don't have a lot of the problems gas ones do. For what it's worth, I think they should last 15-20 years. It's uncommon to have to replace one at 8 years..but it could happen.
If you follow waffleironhead's advice and check the upper heating element... The heating elements screw in and have a rubber gasket that's probably broken down and needs to be replaced. Once you unscrew the element and remove it, you can take it to your local big-box hardware store and find a replacement fairly easily.
See if you can partially drain the hot water heater using the spigot at the bottom below the level of the first element and go from there. There may be a manual with the hot water heater in a plastic sleeve stuck to the side of it. Sometimes they will give you a service manual. If you don't see one, there are probably tons of references on Google...or call a plumber. I just wouldn't waste money on a plumber...it should be an easy fix unless it's something other than the rubber gasket that's leaking.