I second that.
I tried to put 2 tires that were considered "average rolling resistance" according to the euro tire rating system and they killed my range, I went from 4 miles per kwh down to 3.
After 4,000 miles they had gotten a little better but I had to replace them with real high end Michelin tires with an A+ LRR.
Here is a file from a 2011 article that I found a few years ago, but now the link is dead.
I searched around and found the only tire that could beat the ecopia was the energy saver, as far as tires sold in the US.
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Is going to get you.