What is in a watt?

Everyday things, in order of how much power they want. Connect a trainer and pedal, or move the slider, and watch where the list stops.

## A watt is smaller than you think, and a kilowatt is enormous

Most people have no feel for electrical power at all, because nothing in daily life makes you pay attention to it. The bill arrives in kilowatt-hours, which is power multiplied by time, and the two get muddled.

Pedalling fixes that faster than any explanation. When you can personally run the light, and personally cannot run the kettle, the scale stops being abstract.

The thing the list makes obvious is this: anything that makes heat lives in a different world from everything else. A bright bulb is eight watts. A laptop is fifty. A large television is a hundred. One fit person on a bicycle can run all three at once and still talk to you. Then somebody boils the kettle and it wants three thousand — fifteen of you, going flat out, for a cup of tea.

That is not a quirk of kettles. Heating things is simply expensive, in a way that lighting them or computing with them is not. It is why heating and hot water dominate household energy use, why the shower is the biggest number on the list, and why every serious conversation about energy comes back to heat.

## What your own number means

An adult who does not ride can usually hold somewhere between 100 and 150 watts for a few minutes. Someone who rides regularly will sit at 200 to 250 for an hour. A quick amateur does 300. For a few seconds, a strong sprinter can touch 1,200 or more — briefly outrunning the microwave, which is a fact worth knowing.

Set the slider to your own figure and look at where the list stops. That line is the honest boundary of what a human body can do continuously, and it has not moved in all of human history. Everything above it is why we built power stations.

## Why the fridge is a trick question

The fridge-freezer on the list says 150 watts, which is what its compressor draws while it is actually running. But a fridge only runs its motor perhaps a fifth of the time — it cools, it stops, it waits, it cools again. Averaged over a day it is nearer 30 watts.

Almost every appliance plays some version of this game. A washing machine draws 2,000 watts while it heats the water and almost nothing while it turns the drum. A microwave's "800 watts" is the cooking power it delivers, not the 1,400 it takes from the wall. The number on the label and the number on your bill are different questions.

So read this list as what it takes to run the thing at that moment, which is exactly the question your legs are asking.

## Connecting a trainer

If you have a smart trainer or a power meter, the button talks to it directly from the browser. Nothing is installed and nothing is sent anywhere — the watts go from the trainer to the page and no further.

It needs Chrome or Edge, on a computer or on Android. Safari and Firefox do not support Web Bluetooth, so on an iPhone or iPad the slider is the way in. Your trainer also needs to be awake and not already connected to something else; most only talk to one thing at a time, so close the other app first.

If no trainer appears in the list, the usual causes are that it is still paired to a phone in the next room, that it has gone to sleep, or that it needs a turn of the cranks to wake up.