Last Update: September 1, 2015

The Range Anxiety bugaboo is partly about effective trip speed over a long distance. While it's presented as the fear of getting stranded with a dead battery pack, it's also the fear of being unable any kind of trip you want to make. Gasoline car owners are accustomed to driving wherever they want, whenever they want, relying on a ubiquitous network of refueling stations offering a 5 minute full recharge, along with convenience services like coffee, drinks, snacks and restrooms.

Given sufficient charging infrastructure, it's possible to take trips of any length with an electric car. But, a slow charging rate will make the trip impractical, as we'll see below. The charging speed (range gained per hour of charging) is what determines the feasibility of making a long-range trip with a given electric car.

Earlier we said electric cars with longer driving range are more valuable than ones with a short driving range. That's clearly true for trips around town, but what about long trips, proper road trips? Electric cars with fast charging are, as we'll see below, more practical on long trips and therefore are more valuable than those with level 2 charging. Well, as long as your region has a network of compatible fast charging stations.

It boils down to a measure, range gained per hour of charging. Some places publicize a rating like 100 RPH. RPH is Range Per Hour (of charging), hence 100 RPH is 100 miles range per hour of charging.

To start this off, rules of thumb with a typical electric car:

- 6 kiloWatt level 2 charging: gains 20-25 miles range per hour of charging
- 24 kiloWatt DC fast charge: gains 80-100 miles range per hour of charging
- 50 kiloWatt DC fast charge: gains 160-200 miles range per hour of charging
- 120 kiloWatt DC fast charge: gains 300+ miles range per hour of charging
- Gasoline: 300 miles in five minutes, or 3,600 miles range per hour of charging

- 6 kiloWatt: 30 hours charging time - 10 hours driving time
- 24 kiloWatt: 7.5 hours charging time - 10 hours driving time
- 50 kiloWatt: 3.75 hours charging time - 10 hours driving time
- 120 kiloWatt: 2 hours charging time - 10 hours driving time
- Gasoline: 10 minutes charging time - 10 hours driving time

Why do I say a fast charging electric car is more valuable? It's that the faster the charging rate, the more flexibility you have about when and where you can drive your car.

We can also take from this the factoid that, over a long trip, the effective trip speed is dominated by the charging rate.

- 6 kiloWatt: 40 hrs driving & charging time equals 15 miles/hr
- 24 kiloWatt: 17.5 hrs driving & charging time equals 34 miles/hr
- 50 kiloWatt: 13.75 hrs driving & charging time equals 43.64 miles/hr
- 120 kiloWatt: 12 hrs driving & charging time equals 50 miles/hr
- gasoline: 10.1 hrs driving & charging time equals 59.4 miles/hr

To understand this a little more deeply, let's take a look at how the rules of thumb above were calculated.

The EPA ratings label for electric cars shows the kiloWatt-hours consumed per 100 miles. The BMW i3, for example, consumes 27 kWh per 100 miles or 270 Watt-hours per mile, which is a bit less than 4 miles per kiloWatt-hour of energy. As a simplification let's say a typical electric car delivers 3.8 miles per kiloWatt hour of energy, and has a 24 kiloWatt-hour pack.

- 6 kiloWatts: 6 kWh gained per hour, or 22.8 miles range per hour
- 24 kiloWatts: 24 kWh gained per hour, or 91.2 miles range per hour
- 50 kiloWatts: 50 kWh gained per hour, or 190 miles range per hour
- 120 kiloWatts: 120 kWh gained per hour, or 456 miles range per hour

The point is that the range gained per hour of charging is a simple equation: kiloWatt-hours gained per hour of charging, multiplied by the range per kWh of energy consumed.