It's true!

Although it may seem safe to assume that one horsepower is the output a horse is capable of creating at any one time, that is incorrect. In fact, the maximum output of a horse can be up to 15 horsepower,[2] and the maximum output of a human is a bit more than a single horsepower. For extreme athletes, this output can be even higher with Tour de France riders outputting around 1.2 horsepower for around 15 seconds, and just under 0.9 horsepower for a minute.[3]
https://energyeducation.ca/encyclopedia/Horsepower

I must now once again question the nature of reality.

Horsepower is averaged based on an extended time period, how much power a horse can put out on average while constantly working. They can't do 15 hp on a constant basis, they can only do it for a relatively brief period of time, so their average is 1 hp. A 15 hp engine can run at 15 hp for a much longer period of time, which a horse can't do. If the engine was hypothetically capable of working consistently without ever breaking down, it would be able to run at 15 hp indefinitely. But even with the machine's lifespan in mind, it can still run for years at the same output, which is impossible for a horse.

What about B horse?

I think it’s between 1 and 15, depending on factors like how tired, or if his horse girlfriend broke up with him for that dumb old stud.

Watts are superior for this reason.

1 horsepower is supposed to be the rate a shitty old timey horse can work over the course of a whole day. Also it was created as a way to market steam engines to replace horses as a source of mechanical power so there was an incentive to lowball the horse.

There's a difference between maximum power and maximum continuous power. It's like your car engine; it might be rated for hundreds of horsepower, but most of the time cruising down the highway it might be making 20 or so just to keep you loafing along.

So how much HP does Bojack Horseman have?

Li'l Sebastian ran at about ~~5 HP~~ 15000HP! I stand corrected

Every kilowatt has 1000 watts

Interestingly, I read the images as skeletor, if you know what I mean

nyaaaaah

Guess we now have to change to duck power instead