More efficient EVs could be the key to less expensive electric cars and cleaning up the environment.

In a new white paper, the group notes that boosting efficiency allows for smaller battery sizes, which in turn cuts costs. Most EVs average 2.5 miles per kwh, according to the paper, but the Tesla Model Y averages 3.5 miles per kwh. That’s a 40% increase which, assuming similar range, allows for a 40% reduction in battery size that’s worth up to $4,800 in cost savings, the ACEEE reasons.