[rwyler]

Well I decided to do a little math to see if it would make much sense for me to get one of these. I currently get around 33 miles per gallon on my daily commute to and from work (about 25 miles each way), and have gotten as good as 42 miles per gallon driving for long trips on the highway. I just bought my car in January so it's been all winter driving. I attribute the really good mileage on the long trip to keeping the car warm and just running in "steady state" the whole time, as well as not having to deal with the short run to and from the interstate on both ends of my daily commute.

Back of napkin math time:

If I assume half of the mileage difference is from running cold, I could stand to save 4.5 MPG only on my way to work every day (no electric plugs at work) which equates to an overall increase to 35.25 average MPG on my daily commute. That would save about 0.1 gallon of gasoline per day. I have paid $1.82 per gallon on average since buying the car, so I could stand to save 18 cents per day using the block heater. My electricity at home costs about 10 cents per kWh, so if I run a 1000W block heater ($32.58 shipped) for an hour I spend 10 cents heating the car up. That's a net savings of 8 cents per day. That means it would take 407 days to pay off the cost of the 1000 watt heater on Amazon.

Worth it? I'm not sure. If I had a plug at work it probably would be, but I think I'll just live with being a little cold for the first few miles for now. I'm not sure that one of these heaters will even last for 407 cycles as evidenced by the premature failure listed earlier, and my car might not last another 407 cycles either (20,000+ miles). I think there are lower hanging fruit for me. Has anyone quantified the real MPG savings from their block heater?