Every time I see “mAh” on a consumer product, I cringe. Megahertz are starting to bruise, too. That’s because the most critical components of portable gadgets — batteries and processors — should really be measured in watts: it’s the one common spec that gives you a real idea of what your device can do.
With watts, you can tell how much literal power is under the hood — how much energy is provided by your battery and how much is coursing through your chip. Watts determine whether there’s enough cooling to let that processor run free, instead of overheating and throttling prematurely. Watts can even tell you how much battery life you have left, based on the watt-hours (Wh) of battery remaining and the wattage at which your device is draining.
You can do it all with elementary school math — so why aren’t watts everywhere? Consumers are regularly exposed to wattage measurements when buying light bulbs or reading their power bills. But many gadget manufacturers insist on measuring their batteries in milliamp-hours and their chip speed in megahertz or gigahertz, neither of which are a good measure of a device’s true power.
The Steam Deck gaming handheld is my go-to example of how handy watts can be. With a 15-watt maximum processor wattage and up to 9 watts of overhead for other components, a strenuous game drains its 49Wh battery in roughly two hours flat. My eight-year-old can do that math: 15 plus 9 is 24, and 24 times 2 is 48. You can fit two hour-long 24-watt sessions into 48Wh, and because you have 49Wh, you’re almost sure to get it.
With the least strenuous games, I’ll sometimes see my Steam Deck draining the battery at a speed of just 6 watts — which means I can get eight hours of gameplay because 6 watts times 8 hours is 48Wh, with 1Wh remaining in the 49Wh battery.
At its most basic, the watt is a measure of work. It’s the amount of energy it takes to do something at a particular speed, whether it’s heating up food in your 1,000-watt microwave or providing the 2-3 watts a smartphone needs while you’re browsing websites on its screen. It’s also specifically a measure of electricity — watts are volts times amps — and a measure of battery capacity, like my Steam Deck example above. (My colleague Thomas Ricker can also help you calculate watt-hours for off-grid energy storage and home backup.)
Perhaps most intriguingly, watts are used as a roundabout measure of heat. If you’ve ever seen a computer processor with a certain TDP, or thermal design power, measured in watts, that’s the amount of cooling required to run that chip at its normal speed. A chip is only as fast as it can be cooled, which is why watts are more important than megahertz.
Today’s laptops have long broken the 5GHz barrier, meaning their chips can theoretically do work five billion times per second. Phone chips are coming close, too. But in small and constrained battery-powered devices, they can only maintain those speeds briefly before they overheat. It’s why a MacBook Pro with a fan has better sustained performance than a MacBook Air without one, even if they both have the exact same chip. It’s part of why a “15-watt” processor will generally feel slower than a “28-watt” one, even if both can hit 5GHz. More power and more cooling means you’re not just a sprinter; you can go the distance.
Unfortunately, manufacturers aren’t always fond of sharing watts with us. They’d prefer to quote bigger, more impressive-sounding numbers instead, advertising a power bank or phone with a “5,000mAh battery” rather than a 19.4Wh pack. You can convert mAh to Wh, but only if you know the device’s voltage, which is another spec that’s often obscured. Some chip makers even hide the wattage of their chips so you won’t know you’re using a weaker version, such as an 80-watt Nvidia RTX 4080 laptop graphics chip instead of a 150-watt one, though admittedly more power doesn’t always make a big difference.
James Watt left behind a legacy of pushing confusing specs
Manufacturers also prefer to share what percentage of your battery is remaining rather than an actually useful number like the watt. They prefer to let you choose vague power modes like “performance,” “balanced,” and “battery saver,” instead of using the smarter watt so you can decide exactly how fast your battery is draining.
I feel like the Steam Deck and other PC gaming handhelds should be a wakeup call that watts are the better way. It’s wonderful to think “crap, my PC needs to last an extra hour before I get to my next outlet” and make that a reality just by rebalancing an elementary school equation.
But if not, I will blame the inventor James Watt himself, who left behind a legacy of pushing confusing specs. While the watt is a genuinely useful unit of measurement, Watt didn’t come up with it. Instead, he coined a different phrase that’s been misleading people for more than two centuries now.
The watt was indeed named for James Watt, more than 60 years after his death, because of his marketing coup. Watt was the man who first popularized the phrase “horsepower” as a way to sell his improved steam engine into all sorts of industry.
According to Watt’s own biographer, he didn’t even come up with the idea of comparing engines to the horses they could replace; that’s widely credited to steam engine pioneer Thomas Savery. Plus, documents from Watt suggest that his definition of horsepower was based on some back-of-the-napkin math! Effectively, a guy told Watt that he wanted a steam engine that could do the work of 12 horses to turn a 24-foot-tall wheel two and a half turns each minute, Watt guessed each horse would pull 180 pounds of weight, and so one horsepower became 32,400 foot-pounds per minute and was later rounded up to 33,000.
But even though a real horse has significantly more than one horsepower, at least over short periods, the unit of horsepower stuck around. It has become one of the most enduring examples of inventing a spec to help sell products, and it might be the reason we have to endure bullshit specs like mAh now.
Free the watt, or else I’ll start measuring gadgets in horsepower out of spite. The official conversion rate is 746 watts to 1 horsepower. Did you know AMD recommends a 1-horsepower power supply for its latest graphics card? Heck, Nvidia’s 5090 needs three-quarters of a horse’s power all by itself.
There’s no better unit than the watt. I just wish companies would let us know it.
