Calculating electricity usage

[Fr3AkAzOiD]

I'm cooking up something but it's a long ways down the road.
Right now I'm just trying to get some info to see if it's worth it.

First I want to know if my understanding of the electrical system is correct.
Battery starts the car, then battery keeps spark plugs firing and accessories running while the alternator keeps the battery topped off.

Is that correct or does the battery start the car then the alternator directly powers the accessories and keeps the spark plugs firing?


Next...
Anyone know of a way to track how much electricity my car uses for a round trip?
For me this would be about 70 miles to and from work.

I would assume I'd need to connect some sort of meter between the alternator and the battery to tell how much power the alternator is putting back into the battery.
Thing is the meter I have just tells instant current and doesn't keep track of the total. I would assume the total would be recorded as kilowatt hours.
Anyone have a clue what I could use to get an accurate number?

I don't want to just have the care idle in the driveway with all accessories running and take a reading that way as I want this to be as accurate as possible.

[gone-ot]

...as long as the alternator voltage exceeds the "fully-charged" battery voltage (~12.7 VDC), it's the alternator that's supplying the "operating" power.