The question of passenger or cargo weight impact on range comes up in different forms fairly frequently. It’s a reasonable question if you’re not familiar with the physics. Let’s consider the question of how much headwind might be equivalent to an additional 370 lb of cargo. Is it 5 mph or maybe 10 mph? If you don’t know or if these numbers sound reasonable stand by for a surprise.

First some reasonable, simplifying assumptions: 1) the trip starts and ends at the same elevation and 2) the trip is at constant highway speeds.

__Rolling resistance increase__
Let’s say the 370 lbs is added to a 4600 lb Model Y including the driver. That’s an 8% increase. So the rolling resistance increases by 8%.

__Total consumption increase__
At highway speeds, the energy needed to overcome rolling resistance is about 1/6 (17%) of the total energy needed to keep the vehicle going at a steady speed. So the total increase in consumption with the extra weight is 17% x 8% or 1.4%.

__Equivalent headwind__
Before the final calculation, recognize that if you were outside in a 5 mph wind you’d be hard-pressed to notice it. You’d likely say the wind was “calm”. Based on calculations I did for

another thread, a 2 mph headwind increases energy consumption by 4% at 75 mph. For this scenario, the math is 1.4% / 4% x 2 mph = 0.7 mph.

So adding 370 lbs is equal to a headwind of 0.7 mph. This is an order of magnitude lower than “light winds”, which you’d most likely not even consider when trip planning. If there was a prediction for a 7 mph headwind for the whole trip, you might not even be concerned before starting out, yet that headwind would have more than

*ten times* the effect on range than adding the 370 lb.

The moral of the story is don’t worry about weight on long-distance trips, worry about the winds.