"My car runs 100 miles!" instead of "My car runs 100 miles per gallon!", and almost anyone would notice something is amiss. I don't get the difference to mixing "Watts" with "Watts/hour".
Energy is not Watts per hour (Watts/hour), it's Watts times hours (Watt-hours). Sorry for pedantry, but the units are the topic of discussion here.
And in turn, watts are joules per second. Resolve Hours to 3600 seconds means 1 Wh = 3600 Joules. Which is the unit we should be using.
That's got me trying to visualise "mile-gallons", and failing because its dimensions would be "length^4".
I did not imply that at all.
Not knowing the difference in miles and miles/gallon will get you stranded in your car pretty quickly. Now knowing the difference between watts and watts/hour will have almost no appreciable effect on your life. You flip a switch, the light turns on, and you get an invoice a month later.
Sure, but people writing articles on the subject should know better than to mix units like this.