Plugging in a gasoline car (does block heater energy consumption offset fuel saved?)
 

I'm wondering if anyone has kept track of how much energy their block heater is using and how much gas they are saving because of it.
Could you compare a block heater on a gasoline car to a plug in hybrid? both use gasoline but both save gas by being plugged in, so I wonder how many KWH per mile you get in a gasoline car by plugging it in.

I think metro did a study some time back . . . .

I suspect a bunch of people have info, or could easily come up with info.
I ask because here it has been 5 degrees the last few days and my gas mileage has dropped by almost 15%, it also takes me 3 of the 4 miles of driving to work before my engine is warm and starts to blow heat, so an engine heater is tempting.

It was definitely an improvement from cost + co2 point of view, they did calcs to find optimal time on for their vehicle.

I've thought about that, too, but I decided that a 'hybrid' is when there is a second source of energy actually pushing the vehicle. Offsetting fuel use by supplying energy to warm things up doesn't qualify as 'hybrid' in my book, but it's also not a passive mod, like insulating the engine bay or having a coolant thermos.

over the first mile I consistanty see 35-45mpg in the morning not plugged in. 40-60mpg if I plugged in. Temps in the 40-50F. Plugged in for an hour at about 500 watts.

Link to a lab/dyno study showing the effect of pre-warming the engine on initial fuel consumption & emissions:

http://www.defa.com/doc/7642.1070613161.whyxdefa.pdf

Unfortunately, they don't quantify how much electricity they used, so it can't directly answer your question.

I haven't tried to quantify the MPG savings of using mine. Even if my total energy use was higher, I'd probably use it anyway for reasons of comfort & reduced wear.

I did find some useful information on the DEFA web site tho, in their technical manual it states:

so 1,900 watt hours to give a temperature rise where benefit is seen, this is a European company so I think it's safe to assume that it's a modest sized 4 cylinder engine, so a larger car or truck engine is of course going to take more energy and there tests were plugging in for 3 hours when it was -20°C/-4°F.
Sure seems like a better idea then letting it idle or driving with an ice scraper in one hand.

I agree completely, but when trying to explain a new idea I figured comparing it to an existing idea might help, also there has been a bit of talk about people building their own plug in hybrids, even if they only get a mile or two of range and altho that is great for really short trips where you could avoid using any gasoline it seems like a system that pre-warms your car and saves gasoline that way could do just as much good and at a cost that more people can afford.

Nice find!

I'll bet the benefit is even greater if the car is garaged.


From driver/passenger comfort, to safety, to just protecting the engine from cold-start damage, it sure is a better idea.

Now, if one could also combine that block heater with a battery heater, AND a battery charger, so that when you turn the car to "Start" it adds a 50A boost, that would have another (albeit slight) advantage of giving the alternator less work to do when you first drive off in the morning. Many of us operate our headlights in the early morning hours (or have DRLs on all the time), and short winter trips can take their toll on car batteries.