orcishgamer: Dun dun dun, if you said 12 mpg with 22mpg you got the right answer. Now go grab a pencil and prove it to yourself since I know you won't believe me.
nondeplumage: The wrong answer, depending whether or not entirely if it was the right question to begin with. And if you're talking about saving money, the correct answer is trading in the 12 MPG vehicle for a 42 MPG vehicle if 1) you can make up the expense of the vehicle within the time you'd get a new one, and 2) do not ambush yourself by thinking if you have a higher mileage car it's an excuse to drive everywhere more often, and 3) get the vehicle that's useful to you; if you need a truck that gets 12 MPG for specific purposes and then go get a tiny econobox, you're not helping yourself any.
And if you can shave off $200 a month in your electricity bill and not be spending close to nothing a month, and if your goal is to save money, you're doing something very wrong. A far more realistic difference between new appliances and old ones is still more complicated than looking at a couple numbers you hope are right before you bring it home, and the savings may be more like $200 a year.
The reason most people would trade a 12 mpg rig in for a 22 mpg rig is they'd be in the same class of vehicle (usually a light truck or minivan). For most people it's an option of trading same for same, it goes without saying that the more mpg you can trade up the better. The mindscrew that most people fail at is thinking switching out their 32 mpg rig for a 42 mpg rig is a better deal than trading the their 12 mpg rig for a 22 mpg rig. This assumes similar distance driven.
So the right answer is 12 mpg for the 22 mpg, this is the biggest savings. This has very real applications, many folks misunderstood the cash for clunkers program the US ran recently, thinking people were trading in shitty trucks and buying another truck and that this was a waste. They misunderstood that this was better overall investment of the dollars spent than buying everyone who already had a fuel efficient car an even more fuel efficient car.
Appliance savings are always dollars per year in the US, if you've bought an appliance in the last couple of decades you should have come across this. Yes, a new washing machine can easily save you 200 USD per year in electricity over a 35 year old one. This will pay for an average cost washing machine in 2 years time. The Energy Star Program requires a percentage improvement in energy usage out of manufacturers every year, so each new machine will be even better, though only marginally from year to year.
KyleKatarn: I don't see this being a problem if people are capable of producing their own power.
If they can produce clean energy, sure. Right now we're still burning natural gas and topping mountains for coal, though, so energy savings are a big deal.