We all know how to compare horsepower, acceleration, and gas mileage. Practical car buyers know to look at cargo volume, too.
But when it comes to buying your first electric car, there are a few things you need to know about charging.
Like the better-known measurements, the rate at which a plug-in car can charge its battery is a specification you should ask about before you sign on the line.
That's because the charging rate directly affects the time it takes for the car to recharge the battery to its full capacity, and hence its full rated range.
In broad strokes, if you're confident that you can charge your car at home every night--or at work every day--then recharge rate may not be quite so important.
But it could be more important to the next buyer, so we still advise being aware of the rate.
PowerPost Level 1 electric-car charging stations at Portland International Airport
And whether a car offers the ability to use DC quick-charging stations, which are totally different from conventional 240-Volt "Level 2" charging, is always important.
DC quick-charging generally recharges the battery to 80 percent of its capacity in around 30 minutes, as compared to several hours on Level 2 charging. (That last 20 percent takes a lot longer.)
In other words, if you have the option, always go for an electric car with DC quick-charging--and if it's optional, tick that box.
ALSO SEE: Electric-Car Fast-Charging Networks: Competition Heats Up (Jan 2015)
120-Volt and 240-Volt charging
Rates for onboard chargers start at 3.3 kilowatts, which is the standard for 2011-2012 Nissan Leafs, later base-model Leafs, and all 2011-2015 Chevrolet Volts.
Eaton CHAdeMO DC quick charging station, Mitsubishi headquarters, Cypress, CA
Later Leafs above the base model doubled that rate to 6.6 kW, and the 2016 Chevy Volt is up to 3.6 kW--which, GM says, is high enough to recharge its 18.4-kWh battery overnight even using a conventional 120-Volt household plug.
Most battery-electric cars will require a 240-Volt Level 2 charging station for overnight recharge, but a 24-kWh Leaf takes 9 hours for a full recharge at 3.3 kW but 5 hours or less at 6.6 kW.
As of this year, the Leaf now offers a 30-kWh battery as well, which will naturally take even longer to recharge. That's why the higher rate is more important for the Leaf.
European battery-electric cars like the BMW i3 and Volkswagen e-Golf have onboard chargers capable of rates up to 7.2 kW. Most plug-in hybrids, however, are sticking with the 3.3- or 3.6 kW rate.
And all of those vehicles except the Tesla Model S use the same connector, meaning that any 120-Volt or 240-Volt charging station with the expected connector can be used to charge them up.
DC quick charging
Things get more complicated with quick charging, for which there are three standards: CHAdeMO (used by the Nissan Leaf, Kia Soul EV, and Mitsubishi i-MiEV), CCS (used by all U.S. and German brands), and Tesla's Supercharger, which can be used solely by Tesla Model S and Model X vehicles.
While CHAdeMO had a head start in the U.S. market, most new DC quick-charging stations being installed today have one cable each for CHAdeMO and CCS.
Right now, just a handful of cars are sold in the U.S. using the CCS standard--the low-volume Chevy Spark EV and a few German models--but more will be coming over the couple of years, most notably the Chevrolet Bolt EV.
NRG eVgo electric-car charging station
As of today, the U.S. Department of Energy's Alternative Fuels Data Center shows 170 U.S. locations offering CCS fast charging (also known as "SAE Combo"), at a total of 296 outlets.
For the CHAdeMO standard used by the Leaf, Soul EV, and i-MiEV, the numbers are 975 locations with 1,293 outlets. The comparable figures for the Tesla Supercharger network are 230 U.S. locations with 1,496 outlets.
Other locator tools--including the Plugshare and ChargePoint apps--may have slightly different numbers.
So here's how we'd break it down, as a set of rules:
- Ask the seller about the recharging rate of the onboard charger
- For battery-electric cars, avoid anything below 6.6 kilowatts if you can
- We'd also suggest avoiding battery-electric models without DC quick-charging
BMW i3 and Volkswagen e-Golf electric cars using Combined Charging System (CCS) DC fast charging
The charging rate is less crucial for plug-in hybrids, especially those with ranges below, say, 20 or 25 miles--since even those can recharge in a few hours.
As always, chat with one or more current electric-car owners about their real-world experiences with charging at home, at work, and at public charging stations.
You'll find that their first-hand experience will give you a sense of confidence about where, when, and at what rate you can recharge.
[hat tip: Brian Henderson]