It does not mean much:

The MPGe rating is really only useful for comparing the relative energy consumption of gasoline (or hybrid) cars with that of electric cars. The Focus EV uses the energy equivalent of 1 gallon of gasoline for each 105 miles of travel, compared to a hybrid Prius, which would use roughly 2 gallons of gasoline for every 100 miles it travels.

Source: Decoding Electric Car MPG | Edmunds

What might be more useful would be a comparison between CO2-equivalent outputs.

For example, where I live, 56% of the power generation comes from coal-fired power plants which produce “greenhouse” gases.

Switching from a gas powered vehicle to an EV outsource one’s personal gas-produced CO2 output to the coal plant and may not have as large an impact on GHG emissions as you might think.

By EdwardM