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So the MPG rating is based on the power plant emissions per mile's worth of energy consumed by the vehicle and comparing that with gasoline emissions? That's g

by drcube 14y ago

So the MPG rating is based on the power plant emissions per mile's worth of energy consumed by the vehicle and comparing that with gasoline emissions? That's great, but like most consumers I want the MPG based on miles per dollars. For example, if I can drive 100 miles on ~$3.50 worth of electricity (or whatever a gallon of gas costs these days), it would be comparable to 100 mpg. Does Tesla or anyone else put out these numbers?

dbaupp 14y ago
$4 - $8 per 100 mi. Using 38 kWh/100 mi (from the article), and estimating electricity to be .1-.2 USD/kWh from here: https://en.wikipedia.org/wiki/Electricity_pricing#Global_electricity_price_comparison https://en.wikipedia.org/wiki/Electricity_pricing#Global_ele...
veemjeem 14y ago
Wouldn't that be a bit too variable to estimate? If you charge your car during the day, it would cost a lot more than charging at night. I think in the bay area, it's around 5 cents per kWh in commercial zones during off-peak hours, so a full "tank" for the 60kWh battery pack would cost you around $3 -- that's almost the cost of half a gallon of gas!
- cynwoody 14y ago
  For the 60 kwh model, 60 kwh would go 171 miles, so that's 1.75¢ per mile. (Although Tesla claims a range of 300 miles at 55 mph.) I didn't know off-peak rates were so cheap.
- nsxwolf 14y ago
  When everyone starts to buy electric cars, won't we start getting closer to 24 peak hours a day?
  - epistasis 14y ago
    Interesting question! Obviously this isn't a problem that's going to happen any time soon. But if you look at a random day of usage for the California ISO (actually, the only one I could find) [1], peak load was 30,000 MW and between midnight and 6AM load was around 22,000 MW. So that's 48,000 MWh, or 48,000,000 KWh, and at 100miles/38KWh, that's 126 million miles of excess capacity in those hours on the West coast. If the average commute is ~30 miles round trip, that's 4 million commuters in California, just from current excess capacity at night time. Needless to say, it will be a while before Tesla ships 1 million cars in California, much less 4 million. http://www.ferc.gov/market-oversight/mkt-electric/california/CAISO-rto-dly-rpt.pdf http://www.ferc.gov/market-oversight/mkt-electric/california...
  - secabeen 14y ago
    Even if we did, that would be good for the grid. Many power-generation technologies have high start-up and shut-down costs, and are most economical when they can be run 24/7. If we can get the variability of power demand lower, we can generate more power with economical means, and use less of the more-expensive and polluting methods.
deleted 14y ago
[deleted]
cynwoody 14y ago
The article claims 38 kwh to go 100 miles for the 85 kwh model. So, if a kwh is a dime, that's 3.8¢ per mile. The 85 kwh model does 0 to 60 in 4.4 seconds. How many miles per gallon would a comparable gasoline powered street rocket get? Maybe 15 or 20 if you are lucky? Let's be optimistic and say 20. Then, if gas is $3.75, that's 18.75¢ per mile, or about five times the expense.
- deelowe 14y ago
  Modern sports or performance cars (audi, porsche, etc..) get around 20 city and 27 highway these days. Though, the Tesla is still much more cost efficient.
- jlgreco 14y ago
  The appropriate car to compare the Model S to is probably a BMW M5, so yeah, in the 17-22 mpg neighborhood.
dillypo 14y ago
No, MPGe is based on 33.7 kw hours = 1 gallon of gas. It's trying to measure based on energy efficiency, not pollution, and not cost to the driver per mile.
deleted 14y ago
[deleted]
- cynwoody 14y ago
  The article claims the 60 kwh model goes one mile on 0.35 kwh. So, at USD$0.16662/kwh (didn't know the currencies were that close), it costs $0.058317 to go a mile. If gas is $3.35/gal, then you need to be getting 57.4 mpg to be even. However, if, as was quoted up thread, off-peak electricity is 5¢ per kwh, then the equivalent mpg jumps to 191.
baddox 14y ago
Local gas and electricity prices vary dramatically, but it should be fairly simple to calculate this yourself for your area.
SeanLuke 14y ago
> So the MPG rating is based on the power plant emissions per mile's worth of energy consumed by the vehicle and comparing that with gasoline emissions? This sentence appears to be very, very confused. It's not based on emissions at all. It's not energy per mile. And it's not MPG, but MPGe. "MPGe" is "Miles Per Gasoline Equivalent", and is not MPG. This is an odd historical measure of engine efficiency which stems from early attempts to shoehorn natural gas vehicles into CAFE standards. For purposes here, I believe what the EPA did is take the energy contained in one gallon of gasoline (33.7 kW-hr) and computed how many miles an electric vehicle would go when consuming that amount of energy put into its battery. It's useful for comparing electric vehicles to electric vehicles, but not useful for comparing across different kinds of propulsion. What you probably want is Miles per Dollar. This would have to be computed both for your gas car and your electric car, and has to be computed based on the cost of gasoline in your area, the efficiency of your two cars, and the cost of night electricity (most utilities have night-consumption plans for electric vehicles). But my understanding is: at present most people see their electric vehicles costing about 1/3 per mile of a gas vehicle. That doesn't take into consideration the generally lower costs of maintenance as well (gas engines are complex).

by drcube 14y ago

dbaupp 14y ago

$4 - $8 per 100 mi. Using 38 kWh/100 mi (from the article), and estimating electricity to be .1-.2 USD/kWh from here: https://en.wikipedia.org/wiki/Electricity_pricing#Global_electricity_price_comparison https://en.wikipedia.org/wiki/Electricity_pricing#Global_ele...

veemjeem 14y ago

Wouldn't that be a bit too variable to estimate? If you charge your car during the day, it would cost a lot more than charging at night. I think in the bay area, it's around 5 cents per kWh in commercial zones during off-peak hours, so a full "tank" for the 60kWh battery pack would cost you around $3 -- that's almost the cost of half a gallon of gas!

cynwoody 14y ago
For the 60 kwh model, 60 kwh would go 171 miles, so that's 1.75¢ per mile. (Although Tesla claims a range of 300 miles at 55 mph.) I didn't know off-peak rates were so cheap.
nsxwolf 14y ago
When everyone starts to buy electric cars, won't we start getting closer to 24 peak hours a day?
- epistasis 14y ago
  Interesting question! Obviously this isn't a problem that's going to happen any time soon. But if you look at a random day of usage for the California ISO (actually, the only one I could find) [1], peak load was 30,000 MW and between midnight and 6AM load was around 22,000 MW. So that's 48,000 MWh, or 48,000,000 KWh, and at 100miles/38KWh, that's 126 million miles of excess capacity in those hours on the West coast. If the average commute is ~30 miles round trip, that's 4 million commuters in California, just from current excess capacity at night time. Needless to say, it will be a while before Tesla ships 1 million cars in California, much less 4 million. http://www.ferc.gov/market-oversight/mkt-electric/california/CAISO-rto-dly-rpt.pdf http://www.ferc.gov/market-oversight/mkt-electric/california...
- secabeen 14y ago
  Even if we did, that would be good for the grid. Many power-generation technologies have high start-up and shut-down costs, and are most economical when they can be run 24/7. If we can get the variability of power demand lower, we can generate more power with economical means, and use less of the more-expensive and polluting methods.

deleted 14y ago

[deleted]

cynwoody 14y ago

The article claims 38 kwh to go 100 miles for the 85 kwh model. So, if a kwh is a dime, that's 3.8¢ per mile. The 85 kwh model does 0 to 60 in 4.4 seconds. How many miles per gallon would a comparable gasoline powered street rocket get? Maybe 15 or 20 if you are lucky? Let's be optimistic and say 20. Then, if gas is $3.75, that's 18.75¢ per mile, or about five times the expense.

deelowe 14y ago
Modern sports or performance cars (audi, porsche, etc..) get around 20 city and 27 highway these days. Though, the Tesla is still much more cost efficient.
jlgreco 14y ago
The appropriate car to compare the Model S to is probably a BMW M5, so yeah, in the 17-22 mpg neighborhood.

dillypo 14y ago

No, MPGe is based on 33.7 kw hours = 1 gallon of gas. It's trying to measure based on energy efficiency, not pollution, and not cost to the driver per mile.

deleted 14y ago

[deleted]

cynwoody 14y ago
The article claims the 60 kwh model goes one mile on 0.35 kwh. So, at USD$0.16662/kwh (didn't know the currencies were that close), it costs $0.058317 to go a mile. If gas is $3.35/gal, then you need to be getting 57.4 mpg to be even. However, if, as was quoted up thread, off-peak electricity is 5¢ per kwh, then the equivalent mpg jumps to 191.

baddox 14y ago

Local gas and electricity prices vary dramatically, but it should be fairly simple to calculate this yourself for your area.

SeanLuke 14y ago

> So the MPG rating is based on the power plant emissions per mile's worth of energy consumed by the vehicle and comparing that with gasoline emissions? This sentence appears to be very, very confused. It's not based on emissions at all. It's not energy per mile. And it's not MPG, but MPGe. "MPGe" is "Miles Per Gasoline Equivalent", and is not MPG. This is an odd historical measure of engine efficiency which stems from early attempts to shoehorn natural gas vehicles into CAFE standards. For purposes here, I believe what the EPA did is take the energy contained in one gallon of gasoline (33.7 kW-hr) and computed how many miles an electric vehicle would go when consuming that amount of energy put into its battery. It's useful for comparing electric vehicles to electric vehicles, but not useful for comparing across different kinds of propulsion. What you probably want is Miles per Dollar. This would have to be computed both for your gas car and your electric car, and has to be computed based on the cost of gasoline in your area, the efficiency of your two cars, and the cost of night electricity (most utilities have night-consumption plans for electric vehicles). But my understanding is: at present most people see their electric vehicles costing about 1/3 per mile of a gas vehicle. That doesn't take into consideration the generally lower costs of maintenance as well (gas engines are complex).