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Fuel Economy – How many “miles per gallon” will I get?
Because you are using no gas, there are no miles per gallon. EV fuel economy is measured in average miles per kilowatt hour (miles/kWh). Kilowatt hours are what flow out of EV chargers and home electric outlets to fill up EV batteries. More miles per kilowatt-hour is better, just as more miles per gallon represents greater gas efficiency for an internal combustion engine (ICE).
Unfortunately, few salespersons can tell you the fuel efficiency of an EV. Yet it matters. Lower efficiency = more fuel consumption. That means more frequent recharging stops, greater expense for home and road-trip charging[SK1] , Igreater costs for building and fueling power plants, and greater pollution from non-renewable power plants.
An easy way to estimate the average miles per kilowatt hour is to divide the EPA range by the usable size of the car’s battery. For example, if the car’s EPA range is 300 miles and it has a 100-kwh battery, the average efficiency is 3.0 mi/kwh. See the following section for getting the correct battery size figure.
Curiously, Europeans turn mi/kwh upside down and express it as consumption: kwh-used/100-miles of travel (in this case less is better). Be on the lookout for such upside-down numbers when searching the specifications tables of European manufacturers (e.g., Volkswagen).
What is a good mi/kwh number? Here is a table of the ten EVs most often registered in Colorado (from best seller to least), showing their electric fuel economies (PHEV means dual-fuel Plug-in Hybrid Electric Vehicle). A solely electric car is a BEV (battery electric vehicle):
Model mi/kwh Comment
Tesla Y 4.1-4.3 Very nice
Tesla 3 4.8-5.4 Light BEV; best efficiency of the top sellers!
Nissan Leaf 3.5-3.7 Respectable for a very economical BEV
Jeep Wrangler PHEV 1.2-1.3 Big knobby tires on heavy inefficient vehicle
Tesla S 4.1-4.3 Very nice
VW ID.4 3.1-3.4 Moderately economical BEV
Toyota RAV4 PHEV 2.3 Heavier SUV, merges gas and electric efficiently, so good MPG
Tesla X 3.5-3.6 Heavier SUV
Chevy Bolt 4.0 Soon to be discontinued; economical purchase price
Chevy Volt PHEV 4.8 No longer made, but sells used for good value
Range: How far will my EV fuel take me and how much will it cost?
Many internal fuel combustion (ICE) (gas or diesel vehicle) drivers probably don’t know the size of their gas tank. They do know the price of filling it up, though that price can vary widely from day to day and state to state. Competition keeps the price of gas within a few pennies per gallon within a given area, though the cost of fossil fuels varies widely over time because it is sold in an unregulated international market. Events in other parts of the world can quickly change how much you pay at the gas pump.
In contrast, electricity is sold in a regulated local market and does not change quickly. In most US localities, a few charging companies supply most public charging stations. Therefore competition has not yet begun to penalize unusually high prices (nor reward unusually low-priced suppliers). Private charging is tied to regulated grid electricity price. (Not sure what you mean here. Like, Charge Point and Electrify America, or ? The charger companies buy from regulated electric companies, but I don’t think the price they charge at the EV charger is regulated. But I’m not certain about that. It might be that a state or some other contracting authority could set the max cost for chargers built using their grant money?
Charging overnight at home or during the day at a workplace can be as low as 6 cents/kWh. Rarely does home charging exceed 15 cents/kwh (charging at peak times in California may be more expensive). Fueling an EV from home is incredibly inexpensive; even fast charging is a bargain compared to fueling an ICE vehicle. (link: Should my next car be electric?). Some businesses offer free slow charging if you spend time at their business.
When you are on road trips where you want to charge your battery quickly so you can get back on the road, the price of a kWh from a fast charger can be as much as $1.50 per kWh (typically $0.30-$0.60/kwh). Fast charging is more expensive because you need more electronic hardware and power to push the juice into a battery quickly, and charger electricity must be billed without accommodating the radical hour-by-hour variation in commercial electricity prices. Competition has not yet hewn the price of fast charged kWh into a predictable range (prices in California are converging). Fortunately, the charge-finding software in your car or phone can show you where the cheapest electricity is to be found.
The total cost of an EV fill-up depends on the size of your battery; batteries vary in size from around 10 to 150 kwh. Literature on EVs, and the window sticker at the dealer, sometimes report the battery size, but more often report the number of miles that can be driven with a full battery.
This brings up a quirk of EV fuel tanks: sometimes the full size of the battery is not usable. The manufacturers often make the highest and lowest charge states of a battery inaccessible in order to extend the life of the battery as long as possible. Some manufacturers allow most of the battery’s capacity to be used but encourage owners to draw on that “longevity” margin only when they truly need it. For example, a Rivian’s full battery capacity can be used, but normally the top 30% of the tank is not filled, again to extend the life of the battery. The bottom-most 5-10% of a battery may also be restricted, for the same reason. These “bottom” and “top” buffers of the battery complicate the comparison of vehicles, because promotional literature often cites the full (or nominal) size of the battery, yet some or part of that amount may not be available. Make sure the figures you are cited are for the usable portion of the battery.
Range of the Battery
You can multiply the average fuel economy of a specific model by the usable size of the fuel tank to determine the vehicle’s range. A 20-kwh battery in a 3 mi/kwh vehicle will give you an electric range of around 60 miles. Here are the electric ranges of the ten most popular cars in Colorado, grouped this time by whether they are dual fuel (PHEVs) or pure electrics (BEVs).
Type Brand/Model Range (miles) Price (2023, assuming CO and federal breaks
PHEV Jeep Wrangler 22 $47,400 – $66,100
PHEV Chevy Volt 53 NA (used $4,000-$15,000)
PHEV Toyota RAV4 Prime 42 $40,200
BEV Tesla Y 260-330 $37,400 – $42,600
BEV Tesla 3 272-358 $35,900 – $43,200
BEV Nissan Leaf 149-212 $24,500 – $33,000
BEV Tesla S 320-405 $73,700
BEV Tesla X 269-348 $78,900
BEV Chevy Bolt 259 $16,300
VW ID.4 209-255 $35,900 – $50,400
Charging Rate
Traditionally, charger rates are grouped into Levels 1, 2, and 3 (only Level 3 is “fast”).
Level 1
Level 1 is an ordinary household outlet (110 V AC), which produces a charge rate of about 1.2 kw or kilowatts (kw). When taking about charging speed, the instantaneous rate of charge is measured in kw, not kilowatt-hours (kwh). kwh is a discharge quantity over time rather than an instantaneous rate of charge. In two hours you gain about 2.4 kwh (1.2 kw x 2 hours) from a Level 1 charger. The key advantages of Level 1 charging are that no special equipment is needed, and the charging rate is constant. It does not greatly depend on either the vehicle or the outlet.
Level 2
Level 2 charging can be done from an ordinary 220 V outlet. As with Level 1, Level 2 uses alternating current – AC – such as you might have for a clothes dryer.) New electric vehicles always come with a Level 2 charging cord. If you are buying a used EV, make sure you get the Level 2 charging cord that should come with it. Level 2 charging for non-Tesla cars is done through specialized plugs (called J-1772 or the CHAdeMO plug used by Japanese manufacturers) which come with your car. Teslas come with a “destination plug”, which is what they call their Level 2 plug.
Elsewhere (Which EV model will be best for me?) we have described how fast charging plugs are rapidly converting to a single plug type, Tesla’s North American Charging Standard (NACS) for fast-charging. Manufacturers do not yet have a plan to unify the plugs used for slow charging. Like Level 1, Level 2 charging occurs at a constant rate.
Unlike Level 1, Level 2 charging can occur at wildly different constant rates depending on the car and the charger. The weakest Level 2 charges occur at 3.6 kw, whereas some vehicles can take up to 19.6 kw if the charger allows. A further wrinkle is that most household wiring and home chargers do not support charging rates of more than 10.5 kw. If you deeply crave home charging rates higher than 10.5 kw, talk to your electrician. Most people don’t need faster charging rates (they don’t drive that far in a day – see next section), but I expect that oversized charging ports in a home will soon be a selling point for home buyers (as future buyers will have multiple electric cars and less patience).
Level 3 – DC Fast Charging
Fast (Level 3) charging is completely different from the others; the charge rate controller is in the post instead of the car, the voltage is direct current (DC, whereas Levels 1 and 2 are AC), and charging rates are much faster (50 -350 kw) and vary non-linearly with the battery’s state of charge (i.e., 0 to 100%). For these reasons the plugs that connect your car to the Level 3 post must be different from those of Level 1 or 2 chargers, or people would connect incompatible circuits by mistake. Fortunately, North America is rapidly moving to a universal Level 3 charging plug, Tesla’s NACS. See link (Which EV model would be best for me?) for information on adapters that might be needed during the 2024-2026 transition period. Fortunately, the plug-finding software in your car or on your phone (plugshare.com, chargepoint.com, https://abetterrouteplaner.com, etc.) knows where each type of charger is to be found and it knows which your vehicle is capable of mating with, so you need only follow the instructions on the route- finding map you are using. After about 2026 all fast-charging stations should be available to all EV drivers.
An additional complexity of Level 3 charging is that the charge rate is so high that your battery cannot handle continuous charging at the maximal output. The maximal rate of charge advertised by the car brand or charger manufacturer is not sustained the whole time you are plugged in to a Level 3 charger. Charging starts at the maximum level your car will allow and slowly steps down the closer the car gets to its maximum capacity. The car tells the charger what trajectory to follow. You don’t have to do anything to keep the charging on track. This complicates the estimation of charging times (see next section). The key takeaway is that to maximize the charging rate and minimize the time spent waiting for the charger, you want to arrive at a fast charger with the car in a low to intermediate state of charge (SOC). SOC is usually visible on your car’s dash, if only as the number of miles remaining or as the percent full the battery is currently at). The car will charge more slowly if the battery is nearly full or nearly dead. Fortunately, the charger-finding software knows this and will coach you on where best to charge to minimize down time.
To provide some benchmarks for how quickly your car can charge, here are figures for the top ten selling cars in Colorado. The maximum charge rates listed for Levels 2 and 3 are what the car is capable of. For Level 3, a particularly fast charging post is one rated at 150 kw or more. PHEVs in this list do not support Level 3 charging. All rates are in kw.
Make and Model Level 1 Range Level 2 Range Level 3 max
Tesla Y 1.2-1.3 10-11 250
Tesla 3 0.9-1.1 6-9 200
Nissan Leaf 1.1-1.3 6-7 50
Jeep Wrangler 0.8-1.6 6-8 NA
Tesla S 1.2 10-16 220-250
VW ID.4 1.2-1.3 10 161
Toyota RAV4 1.3 6.5 NA
Tesla X 1.1-1.4 10-16 215-250
Chevy Bolt 1.3 10 50
Chevy Volt 1.2 3.6 NA
Note that Level 2, when it is used for recharging after your daily commute, will more than suffice for most commutes. For example, suppose you are driving a Tesla Y for 75 miles each day. Given the fuel economy of the Y (~4.2 mi/kwh) and the daily distance travelled (75 miles), you need only 75/4.2 = 17.8 kwh to be restored to your battery overnight using Level 2 charging. Let us suppose that you have slowest possible Level 2 home charger (=3.6 kw/h) and you are home for only 10 h a night (= 3.6 kwh × 10 h = 36 kwh). That is, your weakling Level 2 charger supplies about double the amount of “juice” needed for your 17.8-kwh commute.
Converting charging rate to miles added for a given amount of charging time
For Levels 1 and 2, the charging rate can simply be multiplied by the number of charging hours to determine the number of kwh restored to the battery. For example, if charging a RAV4 PHEV at its maximal Level 2 charging rate of 6.5 kw for 2.0 hours, the recharged kwh is about 13. Knowing from the first table that the RAV4 has an average fuel economy of 2.3 mi/kwh, one can multiply these two numbers together (2.3 mi/kwh × 13 kwh = 26 miles). In practice, the conversion efficiency is not 100%, but the result will be close enough to provide useful guidance.
Level 3 is more complicated. Two cars at the same fast chargers will have differently shaped charging curves, as well as different allowable maximums, and likely different charge states upon arrival. You can make a ballpark estimate using roughly half the maximum charge rate achieved in the first ten minutes (chargers and many phone apps display the instantaneous charge rate), but most people simply rely on their navigation program to identify the best number of minutes to fast charge. The navigational programs of most current cars seem to incorporate upcoming elevations gained or lost, speed limits, air temperature, and recent driving performance. Some other factors (wind speed and driving style may not be). Most navigational programs also allow the user to set the target for number of miles remaining in the battery upon reaching the next destination. Querulous drivers can boost this safety margin and risk prone ones can reduce it.
Naturally, some people prefer to stop more often for shorter charge bouts than do other people, but that is easy to arrange (assuming an adequate pool of chargers exists where you wish to charge; again, consult your charger finding software). Good charger finding software knows if the chargers on the route ahead are functioning, but they cannot know whether someone else will be using the charger when you get there (plugshare.com provides a 1-10 star score for their best estimates as to the prospects of finding an open plug: 10 is most likely).
