Electric vs Gas vs Diesel: When is a horsepower not really a horsepower?

November 16, 2019

I’ve driven every single fast car, fast motorcycle, big truck, and electric anything I can get my hands on in the past 30 years. I’ve always made a mental note of how many ‘horsepower’ whatever device I’ve been piloting has and what it felt like to drive. There is a substantial difference between the horsepower rating of these vehicles and how much power it feels like that have available. This article is about why there is such a huge discrepancy where there really shouldn’t be. You should take any HP rating with a healthy dose of skepticism on account of whether the power is provided by electricity, gas or diesel.

What is a horsepower

A single mechanical horsepower lifts 550 pounds by 1 foot in 1 second. When you convert it to watts you get about 745.7 watts. Essentially HP is a measurement of how much work you can get overtime.

Which energy source ‘feels’ the most powerful? (and why)

Before I even get into this article I’m going to lay out which power source seems to deliver the most ‘power’ based on what the energy source is.

  1. Electric
  2. Diesel
  3. Gas

Electric motors have almost no moving parts (other than the rotor) and can generate massive amounts of torque from zero RPMs. Any ICE motor cannot do that. They have to be spinning at speed to really generate power, and when you see HP ratings for any motor what you are seeing is ‘peak horsepower’ at whatever RPM generates the most power. There are often fancy transmissions to try to keep these ICE motors in the center of the torque curve, but the reality is that most of the time they are running at a range that is outside their peak HP.

Diesel engines generate more hp at lower RPMs than gas

One of the reasons that diesel engines feel more powerful than gas is that they tend to generate more hp at lower RPMs. They also tend to have much higher torque at lower RPMs which drops off as the engine spins faster. This is caused by a number of things including a higher compression ratio, a longer stroke and an increase of about 15% more energy density than gasoline. Many gasoline engines will beat out diesel for HP at higher RPMs which is one of the reasons that many types of diesel engines have turbochargers on them.

When people buy HP what they really want is torque

So the irony here is that most people buy products with a hyper-focus on HP when what they really want is torque. Torque is how much power the motor can put out to get you up to the speed you want to go. It’s the seat of the pants feeling you get when you stomp the pedal to the floor or twist that throttle and the front wheel comes off the ground. When it comes to torque any ICE motor just can’t compete with electric because an electric motor can deliver 100% of its torque from a complete standstill. The motorheads of the future will probably look at the period of internal combustion engines with a sort of detached nostalgia.

There are a variety of gas motorized bicycle kits that cost ~$150-300

What does this any of this have to do with electric bikes?

If you’ve ever ridden an ICE bicycle you know they tend to come with noisy smelly 2 stroke motors. They are incredibly cheap and tend to be in the 2-3hp range. What you notice immediately is that although they are fast, they don’t have the off the line power that a 1500W + electric bike does. This is because the power of the 2 stroke doesn’t open up until you hit the higher RPM ranges. This brings up another point, HP is a good indicator of how fast a motor is going to be able to go, but not a great indication of how fast you’re going to be able to get there.

The Bafang BBSHD only produces about 2HP but the 160 Nm of force is what really makes it shine

When you start looking at tractors the difference is even more pronounced

I’ve built an electric tractor (with an insane paint job) and it has way more power than its gas counterpart does even though it generally pulls only 6-7 hp while mowing. The continuous power rating of the tractor is around 13HP (the motor is rated for 17HP but only for about a minute).

Scary to look at, more terrifying to ride, this homemade electric tractor blows away the 16HP gas version

I’ve been thinking of getting a ‘real’ tractor for my 42-acre nut farm here, but there is not really anything electric on the market that is cost-effective and appropriate for my application. Luckily I don’t really need a tractor for another 5-10 years when the trees will actually mature. Instead, I’ve been trying to plant about 7000 trees in one year without the use of a tractor, which is an accomplishment in and of itself. One of the interesting videos I ran into was the one below where dude talks about the HP equivalence between gas, diesel and electric. His belief is that if electric HP was the baseline then diesel HP equivalent would be about 1/2 of electric and gas would end up being about 1/3. That means a 20HP electric tractor would be equivalent to a 40HP diesel or a 60HP gas engine. Although this is an absolutely radical claim, it sort of mirrors what I have seen with the differences between electric, gas & diesel.

Keep in mind that when using a tractor you’re often not interested in top speed so a lack of HP in many instances will not really be that noticeable, but a lack of torque absolutely will.

When you start looking at electric motorcycles, you can really see the difference

I’ve owned 5 motorcycles in my life but ridden more than 50 different motorcycles both gas and electric. One of the best motorcycles I’ve ever test-driven was the Zero DSR which is only rated for a measly 70HP peak. Anyone who has ever gotten on a Zero DSR and pegged the throttle will realize that it sure doesn’t feel like 70HP. It feels like from 0-60 that this bike would hold its ground against any other rice rocket out there.

The specs for the DSR look pretty abysmal on paper, but it feels epic to ride

Zero also has a newer model SR/F which has an absolutely insane 110HP and 140ft/lbs of torque. I have not ridden this motorcycle, but I can only imagine how much fun it is to ride. If I was going to buy an electric motorcycle, this is absolutely the one that I would buy.

The sub 500lb Zero SR/F is the premium of the electric motorcycle crop

If you’re going to shop electric vehicles for specs, use torque instead

If you want to get an idea of how much fun that vehicle is going to be, you should look at the peak torque settings instead of HP. The peak torque will show you how much power that vehicle will have off the line and that will translate more into your enjoyment than HP will. Torque is usually referred to in ft-lbs or newton meters (Nm).

Note that 10,000 Nm of torque is the Wheel torque NOT the industry standard engine torque

Unfortudently shopping for torque gets more complicated when industry leaders like Tesla go off in their own direction and start quoting numbers like Wheel Torque when the entire industry uses Engine Torque instead. Wheel torque is a little misleading because on gas motors the wheel torque on powerful cars like the Dodge Demon can generate 14,000 Nm of force in first gear with 91 octane fuel. Check out the video from Engineering Explained below to understand the differences between wheel torque and engine torque.

Electric is absolutely the future of transportation

When looking at a gas or diesel engine the more work you need to be done, the bigger the engine has to be. If you want to tow 20,000 lbs with your truck you are going to need a whopping big V8 to do it. With electric, a motor that will tow 5000lbs vs a motor that will tow 20,000lbs is often nominally bigger. You can use electric motors to tow absurd numbers because the torque is so high from 0 RPMs. Tesla’s new truck may have a towing capacity of 300,000 lbs which is somewhat absurd. Whenever you have that kind of weight discrepancy between the thing towing the weight and the weight it is towing you’re going to have serious issues. On top of that, there are no roads in the US where you can find that kind of weight limit. So for the most part that 300,000lb towing capacity claim is somewhat silly.

I’m going to leave you with this silly video of a BBSHD towing an Audi R8 as food for thought. Although it was really just a publicity stunt, remember that a 2 HP electric motor is going to be a torquey little beast that is going to be mad fun to ride. I just started riding again this winter on my BBSHD 4-year-old Phat Phuk and I had totally forgotten how hard it is to keep that front wheel on the ground. This is why I ride electric bikes, for that insane wheelie feeling with every twist of the thumb throttle.

Ride On.

Karl Gesslein is a degenerate hooligan of the highest caliber living in upstate NY. His passion for e-bikes and all things sustainable causes him to be obsessed with climate change and finding solutions that will keep humanity from becoming extinct from our own hubris. His personal blogs include electricbike-blog.com, awaken-spirit.org & chestnutparadise.com.


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