56 MPG (0.58 kwh/mile)

August 18, 2007 by Rob.

I’ve been trying to track how much power the RAVolt uses. This involves a new ritual where I walk through our spider invested side yard to read the cryptic meter dials every morning and evening. Without a dedicated meter, I’ve had to work out a rough balance between miles and hours of house use. I’m still refining the calculation, but I think it’s pretty close.

The results are that the RAVolt uses about 0.58 kwh of electricity for every mile I drive. If you read my earlier MPG conversion post, (33 kwh/gallon) / (0.58 kwh/mile) = 56 MPG. That’s based on the theoretical amount of 33 kwh of energy in a gallon of gas.

If you care more about $ then here is my savings over gas: 300%. At Austin Energy’s highest residential rate ($0.078/kwh), my commute works out to about 66 cents. My Volvo’s 20 MPG (of plus or premium gas) costs me about $2.50 for the same commute.

The graph below shows my attempt to figure out the mix of car (red) and house (blue) power use based on hours and miles. I ended up using a static 1.6 kw/hr estimate for the house usage. This is not perfect because temperature and time make a difference in the house power use, but it appears to be pretty accurate.

The graph below shows the match between my estimate of car load from the meter and actual miles driven. One deficiency is that I don’t factor temperature or difficulty of the driving into the calculation. Accuracy is nice, but not super critical: the information is just for my edification.

If you’ve got some statistical background, the graph below has some meaning: it shows the correlation between miles driven and estimated power use. Ideally, all the points would lie on the line showing a 100% correlation. This graph shows an even distribution and indicates that I’ve got a pretty good rough estimate.

Posted in Daily Use, Pictures, Storyline, Conversion, Planning | 2 Comments »