I think you meant 0.1 miles per kWh. If the Leaf gets 32 kWh per 100 miles then
100% * 0.1 / (100/32) = 3.2%
That's actually seems pretty good. At $650/yr in electricity costs that's about $20/yr.
These ecomods stack and you also get better range, lower electricity bills and a better battery life.