[kamilner]

The amount of energy from a 1 tonne mass dropping 1 meter is about 10,000J (https://www.wolframalpha.com/input?i=%281+tonne+*+9.82m%2Fs%...)

The amount of energy stored in a Tesla is about 100kWh or about 3.6e8J.

You would need 36,660 tonnes suspended by a meter to store an equivalent amount of energy (or 1 tonne suspended 36.7km). https://www.wolframalpha.com/input?i=100kWh+%2F+%281+tonne+*...

[addaon]

Or one Tesla Model S (~4600 lbs) suspended 17.6 km. With a range of ~400 miles, this means the storage-Tesla would have to drop ~0.027 units per unit travelled by the drive-Tesla, giving a "glide ratio" of ~36:1, which passes the sniff test on reasonableness.