The question came up a few times before we purchased an electric car as to how much it would cost to operate. It was widely expected to be cheaper than a gas car, but by how much? Would it be marginally better or magnificently better? Was there a number we could put on it? Before we even purchased the car I had to figure out how much it would cost to operate.

First off, we should probably talk about what a kilowatt-hour is. But before that we should talk about what a watt is! A watt is a unit of power and is used to describe the rate of electric draw of something. That is sort of misleading physics-wise but will work for a blog post definition. Your 60 watt light bulb uses — you guessed it — 60 watts. A hair dryer uses about 1,500 watts, and a box fan uses about 40 watts. A kilowatt is simply 1,000 watts. So I don’t have to type it too much watts are abbreviated as W and a kilowatt is abbreviated as kW.

This doesn’t take into account the total power usage over time, or energy. (Energy is a pretty fundamental concept in physics and is massively important in terms of electric cars and efficiency. There will certainly be more about energy later.) This is simply the wattage multiplied by the time the appliance is used. If you burn a 60 watt bulb for 10 hours you’d use 600 watt-hours, or 60 Wh. This is exactly the same as if you’d use a six watt appliance for 100 hours, or any combination of wattage and time that equals 600 Wh. As you might expect, a kilowatt-hour is the energy used when 1,000 watts is used over an hour, or whatever is equal to that. It sounds fancy, but kWh is the basic unit of power in regards to electricity.

kWh is also how your electrical company bills you for electrical usage and this is what your electric meter measures for your household. Around where I live, a kWh, counting taxes and fees, costs us about $0.12. Some people pay more or less than 12 cents based on where they live and where their energy comes from, etc. I live in the midwest so it’s probably a typical value here.

The Ford Focus Electric has a battery capacity of 23 kWh. If we take that and multiply it by the cost of electricity we get how much it’ll take to “fill” the battery up. It is $2.76, about the current cost of a gallon of gas. Is that expensive or not? We don’t know because we don’t know how far the car can go off of that.

The EPA estimated range of the car is listed as 76 miles. So by paying $2.76 we can go 76 miles. Is that good? Well, it averages it to cost about 3.6 cents per mile. Every mile driven costs 3.6 cent! Compare this to our old Cavalier and Saturn which did, at best, 30 miles per gallon. A gallon, which costs roughly $2.76 can get us 30 miles. This is an average of 9.2 cents per mile! The electric car costs less than half the cost to operate on a per mile basis as does a Chevy Cavalier and a Saturn SL2, which are fairly fuel efficient cars.

What about for a month? What would an electric car cost then? Driving 600 miles at 3.6 cents per mile gives us a total of about $22 per month.  Compare this to the 30 mpg gas car and that would cost about $55. A 15 mpg vehicle would cost $110. Electric cars, even if they will raise your electric bill a tiny bit, more than offset the expense of buying gasoline. And it’s not even close, they’re about half as expensive as a “good” gasoline car. The savings are more if you drive a truck, SUV, or sports car with a large engine.

That was all just an estimate that I did before I bought the car. I didn’t know exactly how much electricity the car would use compared to these figures, but the real values are close. There’s a few more issues to deal with in the real world though.