Yes. The way I remember it is, watts are actually a measure of power, of rate of energy usage. Here, power is energy per unit time (it can be defind in other ways as well).
Thus, when the news says something like, “Ontario peaked at an electricity use of 26 gigawatts today, and we didn’t have a single network failure!”, that means the province was using electricity at a rate of 26 GW.
The actual SI unit for quantity of energy is the joule, but most people are used to seeing quantitiers of energy expressed in kilowatt-hours from their electricity bills.
One watt is one joule per second. Iif you extend this rate of usage for a period of time, you end up with a quantity of energy again: the total quantity of enegy used (or transmitted or whatever) during the period of time.
The wattage tells you the rate of energy usage; multiply the wattage by the time the devices are on to figure out how much energy was used. Thus if you use a 1000-watt hair dryer for five minutes, you have used:
1000 W x 5 minutes = 1000 J/s x 5 min = 1000 J/s x 300 s = 300 000 J.
If you use energy at a rate of 1 kW for 1 hour, you use 1 kilowatt-hour:
1 kW·h = 1000 W x 1 h = 1000 J/sx 1 h = 1000 J/s x 3600 s = 3 600 000 J = 3.6 MJ (megajoules).
Typical wattage ratings (rates of energy usage) can be measured for various electrical devices around the home. I bought an “energy meter” at Canadian Tire for $25: you plug it into the wall and plug something into it and it measures peak and average wattage (among other things), and totals this over time to show you how much energy was used.
My hair dryer draws 800 W, my mixer draws 400 W, but I only use them for 5 minutes at a time. My computer draws around 200 W, and it’s on for hours at a time. My monitor draws 135 watts, and it’s on for hours at a time too. Then there are things like lamps (9W, 14W), and there are small devices like my cable modem and cable phone gateway, which are on all the time (and probably shouldn’t be).
I happen to have my hydro bill here (I was calling Toronto Hydro Electric System to ask them why they billed me for four times my usual electricity usage, but that’s another story…)
It says that, in the last three months, I used 1348 kW·h of electricity. This is a quantity of energy, and could be expressed as 4.8528 gigajoules.
They also derive a daily rate of energy usage, which is expressed as a bar graph; it looks like about “20”. They express this in kW·h/day! Surely it could be expressed in watts? Then I can compare it to the measured wattage used by various appliances. (I saw the bill and wondered whether something had gone wrong with my fridge or something…)
So… 20 kW·h/day = 20 x 3.6 MJ/day = 72 MJ/day = 72 000 000 J/day = 72 000 000 J / 88400 s = 833 J/s = 833 W.
An average continuous usage of 833 watts. In the previous eight billing periods, my average usage had been around 7 kW·h/day, or 292 W.
