I would suggest calculating your round trip into two different one way calculations. Simply doubling the output number will give you horribly false impressions on power consumption, especially in a hilly area. Just imagine all the power you are going to lose going up that giant 10,000 foot hill that topped off your battery on the way down!
We first need to turn driving directions into lat/long's for our program to read. I am not google, and I do not have a way of generating driving directions and pulling out all the raw data. Maybe its possible via API, i don't know.
1. Have it create some driving directions
2. Right click on the first item it created in the list (probably has start address)
3. Save place as...
4. Save it as a .kml, not a .kmz
Google earth gives us no altitude for each of the points it generates. Boo. GPS visualizer will help us fill in the blanks by getting all the altitude data for us!
1. Visit http://www.gpsvisualizer.com/elevation
2. Click upload file (that is the file we generated from google earth!)
3. Select Output, Plain text.
4. Select Units, feet.
5. Click "Convert and add elevation"
6. You should get a page that has a file you can download, and the data in a text box. We are going to
use the text box data!
1. Scroll down past the directions where you see the NED1 stuff
2. Ignore the first line, copy everything after this until the end
3. Paste it into the text box on this website
4. Don't mess with the kW values unless you have better ones
5. Take a look at the distance data and estimated kW consumption
It is probably going to take a while before I am able to tune this exactly to the LEAF, so for now, take any data with a grain of salt. Eventually, I hope to have driver profiles, other EV's, and perhaps even gas cars (for you hypermilers out there) supported with drop downs?
Here's part of my commute for an example. Copy and paste this if you are too lazy to calculate the above :)