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My calculation is that if you charge batteries for an electric car, then run the electric car from the battery, good net energy in from the utility transferred to motion is not that great.

The utility delivers maybe 25% or so of the BTUs burned to generate electricity to your home. (A turbine is about 30% efficient, average line losses are around 7%, so 0.3 x 0.93 = 0.27, or approximately 25%.) Then you charge your battery and discharge the battery. That process evolves heat in the AC/DC converter, (which may be more or less efficient) and in the batteries. I've seen figures as low as 10% for watt-hours in vs. watt-hours out, but let's say it's a good battery with high recovery ratio of 80%. Then there is some inefficiency in the electric motor, although they can be very good, better than 85% conversion.

That means that the EV is getting around 0.25 (utility) x 0.8 x 0.85 = 0.17 or 17%% net efficiency on BTUs of fuel, and it could easily be 1/4 of that with badly maintained batteries, worn out AC/DC converter, longer distance of electricity transmission, etcetera.

Compare that with the efficiency of a well tuned gasoline engine, which gets around 30% efficiency of BTUs burned to motion generated.

It appears to me that an EV vehicle should consume twice the BTUs of fuel (as coal or natural gas) as a standard car to accomplish the same motion. That would suggest, that unless the power is produced by hydroelectricity or nuclear power, an EV probably has a worse overall carbon footprint than a standard car.

Comments and thoughts welcome. I've been mulling this over for a while. :bananalama:

Your probably gonna need to site sources. I'd start with Argonne Labs GREET reports. I've done similar work and didn't find electricity lossy to the scale of 83%. Also, don't confuse wheel-to-well with theoretical-thermal-efficiency. I never quite found EV to be dirtier than gas powered. The best I got was something along the lines of "The Best Gas car == The Worse EV" as far as emissions and BTU waste goes. My goal was to keep EV makers from being so sloppy that they ended up in that cross-over region.

11011011

My last reply to similar such subjects:
Ahh my favorite subject...

The official numbers will be in the GREET reports. Here's one sample report here, but there are VOLUMES more GREET data to read through.
http://www.transportation.anl.gov/software/GREET/pdfs/esd_bv2.pdf

My threads on the subject:
Why Can't the Media Measure PHEV MPG?
List of Historical EV efficiencies
Tesla -vs- Insight high-score

Files I've released on the subject:
MPGge Calculator (http://www.cleanmpg.com/forums/downloads.php?do=file&id=28)

To summarize my findings. 80 MPG is more efficient than 200 Wh/mi, but that is based on regional (Texas) grids. Clean grids like California greatly favor EVs in GHG comparisons. Other super dirty grids greatly favor gas powered cars in GHG compares.

11011011

Welcome to CleanMPG, but why did you join?

Typically people join, identy their ride so we can help out.

Instead, you have made an assertion about EVs and maybe plug-in hybrids that is questionable and without supporting links.

This is a site about hypermiling - tell us about your ride.

My calculation is that if you charge batteries for an electric car, then run the electric car from the battery, good net energy in from the utility transferred to motion is not that great.

The utility delivers maybe 25% or so of the BTUs burned to generate electricity to your home. (A turbine is about 30% efficient, average line losses are around 7%, so 0.3 x 0.93 = 0.27, or approximately 25%.)

Actually, the average HRSG-equipped power plant will be between 55%-80% efficient once its all said and done. I know, I designed powerplants for a living.

I am sure this footprint will vary by region. In the northwest, nearly all power is generated by hydroelectric means ... but in a region powered by coal or diesel plants, the footprint would be much larger.

Generally speaking, its cleaner to centralize fossil fuel power generation rather than put it into every vehicle. This is inefficient.

Also, power suppliers and/or government could quickly change large swaths of vehicle efficiency by switching to or or supplementing the grid with cleaner power (new wind project, solar, nuclear, etc.)

The total cycle of electricity for an EV may not be very efficient, but neither is the burning of liquid fuel in an ICE. I'm sure that a BMW M5 is more efficient at peak output than a base model Civic (in terms of energy use per power output) but so what? The Civic still uses far less fuel, because it doesn't need as much power to move it down the road in the first place.

Remember that an EV uses a lot less energy to begin with -- in part because the vehicle itself must be very light and efficient due to today's battery limitations.

Almost any EV on the road requires a fraction of the energy per mile of even the most fuel efficient ICE car. Even with coal generated electricity an EV has a smaller carbon footprint per mile than a Prius.