Answer: About twice as efficient as the most-efficient electric cars.
That’s much better than gasoline-powered motorcycles, which are roughly as efficient (MPG) as the best gas (hybrid) cars.
Here, we’re only talking about so-called highway motorcycles, that is, those capable of cruising comfortably on an interstate highway.
That highway cruising is the main reason that electric motorcycles don’t do better. You might think that a 500-pound single-passenger motorcycle would be vastly more efficient that a 3500-pound multi-passenger car. But at highway speeds, it’s all about wind resistance. A motorcycle with an upright rider has a terrible coefficient-of-drag, which means that pushing it through the air at highway speed takes a lot of energy.
Note: All artwork for this post is via Gencraft AI, with a base prompt of “electric motorcycle”.
Background: What the point of this?
I haven’t owned a car for about a year now. After I got rid of my last car (14 years old, just over 45K miles), it seemed wasteful to buy another. I just don’t drive enough to warrant owning one.
For now, if I need to drive somewhere, I borrow my wife’s car. Occasionally, that’s inconvenient, so I’ve been pondering my transportation options, for something less than a new car. Maybe an old used car? E-bike? Motorcycle? Scooter?
This post is one part of that: How efficient are electric motorcycles?
The EPA drive cycle.
Source: EPA.
Before you buy a car in the U.S., you get a pretty good estimate of the gas/electric mileage you can reasonably expect via the EPA mileage rating. That’s because the EPA (effectively) puts all cars through the (roughly) the same set of “fuel economy test cycles”, like the one shown above.
YMMV, but at least you get an apples-to-apples comparison across new U.S. vehicles. The need for a specific drive cycle, in order to benchmark mileage, is why you can’t compare the EPA estimate to estimates from other countries, say. Different countries use different drive cycles. A “gentler” drive cycle will produce better mileage. The U.S. procedure underwent a major revision in 2008 to provide a more realistic simulation of typical (bat-out-of-hell) U.S. driving, and underwent minor revisions in 2017 to accommodate newer technologies (hybrid, electric). This, per fueleconomy.gov.
Gas motorcycles? Once upon a time, these were considered fuel-efficient.
But motorcycles didn’t change much. While cars did.
For gasoline-powered motorcycles there is no such standard fuel economy testing in the U.S. (per fueleconomy.gov). All you can do is scrape up whatever official or semi-official mileage claims you can find. At the end of the day, you don’t know much, because you don’t know how manufacturers (or others) derived those claims.
Before going further, I need to make the same distinction that the EPA makes regarding motorcycles, in regulating emissions. The EPA uses “highway motorcycle” to separate those capable of cruising at highway speed, from (e.g.) low-powered dirt bikes that may or may not be street-legal. Not to mention various scooters, which literally only means that the vehicle has a step-through frame, but is typically associated with low-powered motorcycles that can’t travel fast enough to be used on the highway.
Here’s a condensed list of what was billed as the most efficient motorcycles in each class, from an article on a topspeed.com, a seemingly-reputable 20-year-old Canadian website dedicated to all things automotive. The 2023 Prius is shown for reference, using the EPA rating from fueleconomy.gov.
- Touring — Harley — 45 MPG
- Sport — Ducati — 47 MPG
- Cruiser — Yamaha — 51 MPG
- Naked — Husqvarna — 53 MPG
- Adventure — Yamaha — 53 MPG
- 2023 Prius — 57 MPG
- Sport — BMW — 63 MPG
- Dirt — Honda — 75 MPG
- Commuter — Honda — 75 MPG
- Cafe Racer — Royal Enfield — 78 MPG
(I excluded the Honda Grom and various mini or pocket motorcycles because those either aren’t street legal, or cannot comfortably be ridden on interstates. The Grom, for example, has a top speed of just about 55 MPH. That ain’t gonna hack it on the interstates around here.)
The upshot is that while options for a fuel-efficient car have expanded vastly over the past two decades, motorcycles are still pretty much stuck in the past. As a result, based on claimed fuel efficiency, many new gas motorcycles get worse gas mileage than a new Prius.
No new highway motorcycles come close to the 133 MPGe that the Prius Prime gets when driven in electric mode. And per seat-mile, a Prius with four passengers is vastly more efficient then even the most efficient highway motorcycle.
Separately, there’s an issue of expected service life of the typical motorcycle. It appears to be much shorter (fewer miles) than the average car. But the discussions I’ve found for that were so larded with bullshit that I never did find any statistics that I thought were worth quoting.
Electric highway motorcycles, about twice as efficient as the best electric cars.
Now we reach a true information desert. All I can do is compile a smattering of whatever-anybody-says regarding range, divide by nominal battery size, and take the overall median, as shown above.
For reference, an efficient EV (or hybrid traveling in EV mode) will get about four miles per KWH, using the EPA drive cycle. I think the entire Tesla clan is in that neighborhood, as is the Prius Prime. Hyundai Ioniq. And a few others.
Also for reference, motorcycles typically get much worse mileage on the highway than in the city. That’s because a typical motorcycle, with upright rider, has an abysmal coefficient-of-drag (COD). Where a Prius might have a COD of 0.24, a old-style boxy Jeep might have one of maybe 0.50, a typical motorcycle/rider has one of greater than 0.65. It takes a lot of energy to push that awkward shape rapidly through the air.
N.B., As I recall it, coefficient of drag is the ratio of an object’s cross-sectional area, to the area of a square that would generate the same amount of wind resistance. Thus, a Prius has about the same wind resistance as a square that’s about one-quarter the cross-sectional area of the car. Lower is better.
If I had to speculate on why this difference between gas and electric, it would be that gas motorcycle engines are optimized for power-to-weight ratio, not efficiency.
Conclusion: That’s a big NO on motorcycles.
As stated earlier, I’m trying to figure out what, if anything, to buy to replace the car that I got rid of about a year ago.
I think this little bit of research was enough for me to dismiss motorcycles of any sort.
If an electric motorcycle were some sort of miracle on two wheels, I might consider trying one. That, despite the obvious weather-related drawbacks, and significantly higher risk of injury.
But, as it stands, the real killer is the enormous cost per ton of C02 emissions avoided. If I’m doing this “to save the environment”, is the purchase of an electric motorcycle, in a household that already has a Prius Prime, a cost-effective move? Or would I be better off spending my money on (e.g.) more attic insulation?
The electric motorcycle would produce about half as much emissions per mile, compared to my wife’s Prius Prime in electric mode. But at an enormous cost per ton of C02 emissions avoided.
In round numbers, if I drove the motorcycle 3000 miles a year, for a decade, rather than drive my wife’s car, it would save just over one ton of C02 emissions. Assuming I could get one for $12,500 (there’s a BMW available at that price), buying an electric motorcycle, when my wife already allows me to drive her Prius Prime, would cost over $9,000 per ton of C02 emissions avoided.
That’s not even close to being in the ballpark for a cost-effective C02 emissions reduction. Restated, for that amount of money, there are a lot of other things I could do that would produce much more C02 reduction.
It’s an inconvenient, less-safe mode of transport, not suitable for all weather. And it’s an expensive way to reduce my carbon footprint, given that we already own a fairly efficient car (Prius Prime in electric mode). It’s a neat concept, but it’s not for me.
