What is Horsepower And How Does it Relate to Performance?

horse power
Never underestimate the power of the horse

Horsepower, it’s funny that such an archaic method of measuring power is still the number one indicator of how powerful an engine is in anything from a formula 1 car to a lawn mower. Of course the real question is, what is a unit of horsepower, and how does that translate to the performance of an engine?

The word horse power was coined by the man who also happens to lend his namesake to an even broader measurement of power, James Watt. Watt lived through the first industrial revolution at the turn of the 19th century, and during that time devoted much of his life towards the development of the steam engine. At some point Watt was said to be working with ponies pulling carts of coal out of mines and noted that they could move the coal at a rate of 22,000 so called ‘foot pounds’ per minute. To scale up this figure to match what a horse could achieve, he scaled up by 50% giving 33,000 foot pounds per minute. Whilst this all sounds completely arbitrary (and to be honest it is), amazingly this same unit of measurement is used today in the latest cars, garden appliances, and even things like vacuum cleaners.

If you’re looking through the specification for a tool and find that the power rating is only provided in another unit such as Watts, then it’s worth knowing that horsepower can easily be translated into other units of measurement. For example 1 horse power is equivalent to exactly 746 Watts, so a typical basic 1200 Watt lawn mower kicks out 1.6 horsepower. Simple enough eh?

It probably won’t have much of a deciding factor on your choice of lawn mower, but if we look at the world of high performance cars we begin to see why horsepower as a standalone measure of a vehicle’s performance is largely meaningless. Instead you need to look at the overall power to weigh ratio. Depending on how the ratio balances out, a car with low horsepower but with relatively lower weight as well, could in theory out perform a car with much greater horsepower but that also weighs an absolute ton. After all, the more weight you’re having to shift, the greater the horsepower you’ll need to accelerate it.

So whilst we’re not dealing with the same issues in terms of acceleration and performance that we would be with a car, it is still worth keeping in mind the theory behind a decent power to weight ratio when buying lawn mowers, trimmers and chainsaws, not least because light tools are easier to carry and operate, but also because they’re more economical thanks to the easier time their motor or engine has when driving them. So by all means check out the power of the engine first, but make sure you keep in mind the weight before making any decisions.



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