Chapter 2 of 8
The faucet and the bucket
A watt is how fast. A kilowatt-hour is how much, and it’s what you pay for. Try it: pick something, drag the time, watch the buckets.
Open the faucet with…
4.5 kWh
1.5 kW × 3 hours = 4.5 kWh, which costs $0.79
Every plug-in heater is 100% efficient — a “more efficient” one is a marketing story. 1,500 W is 1,500 W.
A watt is how fast.
How hard the faucet is open. A phone charger trickles at 5 watts. A space heater gushes at 1,500. A watt says nothing about your bill on its own, because it doesn’t say for how long.
A kilowatt-hour is how much.
One full bucket. It’s what you’re billed for: 1,000 watts flowing for one hour, or 100 watts for ten hours, or 5 watts for eight and a half days. Your utility charges about 18¢ a bucket.
The pattern you'll see everywhere
Two ways to fill a lot of buckets: a big faucet for a little while (dryer, oven, water heater), or a small faucet that never closes (fridge, cable box, porch light). Anything that makes heat is a big faucet. Almost nothing that makes light or computes is.
Watts are speed. Kilowatt-hours are amount. You pay for amount.
Try it: the space heater for three hours fills more buckets than the phone charger would in a year of nights. Next, we’ll draw the buckets on a map of your house.