Are you driving like a grandma slow acceleration or are you driving at low speed? The latter is much, much more important at highway speeds. Apparently the EP

Are you driving like a grandma slow acceleration or are you driving at low speed? The latter is much, much more important at highway speeds. Apparently the EPA test is run at 60mph Max and an average of 50mph, which would to a significant extent explain the difference if you averaged 65mph or similar. They also weight and combine it with city miles, which is probably even more generous to EVs with regen braking.