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

[Ryland]

Originally Posted by AlaricD

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.

That company that MetroMPG linked to DEFA WarmUp - Start page offers a battery charger with their package option with temperature compensation to maintain proper voltage in the cold.
I don't think its a good idea to offer a device that encourages you to start your car while still plugged in, but topping off the battery before you start your car seems like a good compromise.

[brucey]

I feel, once the cost of electricity is factored in we're not saving a lot of money, and I wouldn't be surprised if it's a wash for some folks.

That said, I plug in whenever I remember I'm going somewhere. The warmed cabin, no high idling, relief on the engine/alternator, warmed oil, etc is worth it. The MPG boost is just a bonus.

[Piwoslaw]

Originally Posted by Ryland

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

That sounds about right. My 550W DEFA heater rasies coolant temperature ~20°-25°C above ambient after 90-120 minutes. I haven't tried longer, but I'll test it soon (maybe this evening?).

[Ryland]

So 3 hours of a heater being plugged in draws about 2kwh, or enough to push an electric car 4-6 miles on a good warm day... maybe half that in the winter, seeing as how you are asking your gas engine to work in less the ideal weather we should be fare here.
It seems like someone should be able to set their scan gauge to show water temp (as that is what the block heater would heat) and average mpg for that trip, do a warm and a cold test when it's -0F out and give us some feed back? I don't have any mpg read out for my own personal vehicles so I can't do this at this time.

[SentraSE-R]

When I lived in snow country, I plugged in. The point isn't how much energy you use or save, and it's not comfort or window defogging. It's massive wear on a cold engine. If I still lived there, I'd heat the battery, oil, and engine coolant.

[TomO]

HERE's my math on when I installed my Engine Block Heater in my VX.

The EBH has more than paid for itself now, and I actually plug it in year round if the temps are below 80°F and I know an hour beforehand if I'm going to be driving somewhere.

[Ryland]

Tomo, Any idea how accurate that cold engine 25mpg figure is? I can't remember if you have an MPGuino or not.
And what type of engine heater do you have? oil heater, coolant heater, stick on block heater?

[GeneralAnarchy]

There is another factor sometimes to consider in EBH cost calculation. The heat that leaves the engine compartment is sometimes considered totally wasted. But that's not the case if your car is in a garage. If you leave a 500W EBH on for 10 hours it will use 5kWh. Even if you suppose only 2kWh aids the engine warmup, that's 3kWh that heats the garage and indirectly the rest of the car. The EBH-powered engine block is no less efficient that a space heater once it gets close to equilibrium temp.

I had tried carefully for many years to time my EBH to come on 2 or 3 hours before startup, but now I realize that my effort is better spent on insulating and weatherstripping the garage itself. For that reason, sometimes I think I might as well switch on my EBH at night as soon as I hit off-peak rate and consider EBH to be just another home heating appliance. For those who have natural gas, of course, my conclusion does not make sense.

[IsaacCarlson]

PROPANE!!???? Thats a seven letter word!!!! We heat with wood. It used to cost $2-3,000 just to heat the house for a winter and keep it around 60°F. Now we use wood and it is a nice balmy 80°F and it costs about $100!

We will probably use about 3 cord this year. I sure don't mind the work.

[GeneralAnarchy]

Originally Posted by IsaacCarlson

PROPANE!!???? Thats a seven letter word!!!!

So true. It's propane's dirty little secret. I'm familar with that $3000 heating bill. Even with high-efficiency furnace, for me propane cost was 2:1 compared to resistive electric. That's why I mostly switched to electric. I have no time for wood.