mpg ceiling

[MMUK]

>... 310mpg ...

Clearly a meaningless number if you can only count part of the energy input. So why do you want to record it?

[pb]

I completely understand the impulse the record and share fuel consumption--it's why we built this site! I don't agree that it's completely meaningless, but I agree that MPG is only part of the equation with electric cars. It means that Fuelly isn't quite the right tool for electric car owners to use to track and share their consumption right now.

We hope to change that in the future, but until we find a way for people to report the whole picture they'll need to find another way to track.

[JHatchett]

I am not sure why you would not support adding kWh as a fuelup, along with gasoline, and reporting MPGe.

This seems to be standard forwarded by the EPA.

[pb]

We don't support that because there's no unit of action associated with that. How do people measure kWh? Do they have meters on their electricity for that particular outlet so they know how many kilowatts they're specifically adding to their vehicle?

Adding electricity to a vehicle is not like adding fuel to a tank. There's no objective measure of how much you're adding.

[pb]

Does the EPA provide a place to report your kWh consumption? Maybe we could use them as a model if they've found a way to do it.

[JHatchett]

the PHEV vehicles like Prius Plug In and Volt have either dashboard kWh consumption displays and/or reporting. when they use a public charging station they usually get a total kWh like a gas pump.

Generally, if they are dashboard readings they need to be adjusted for kWh at the outlet to match EPA method for MPGe. typically multiple by 1.15 to account for charging losses.

http://www.fueleconomy.gov/feg/label...EV-label.shtml

The EPA "your MPG estimates" uses only the gasoline, without a 200mpg ceiling.

http://www.fueleconomy.gov/mpg/MPG.d...amp;details=on

[pb]

Thanks for the extra info. Does the dashboard number change after every charge? So I guess I'm wondering does it list kWh for a specific timeframe or a specific charging action? I'm trying to know when would it be a natural time to jot down your electricity usage? After every charge? Once/month?

[BDC]

And also importantly does it count the energy wasted in the charger, separate from the car? My guess is no.

[tofferr]

Regarding the natural time to record the kwh used... I've been doing that when I put gas in my Plug-in Prius. I have a trip setting that tracks kwh used, and I reset it each time I put gas in the tank (about every 3-5 months).

Regarding the energy wasted in the charger: I think it is reasonable for Fuelly to simply record the charge reported by the car at the battery, since that appears to be the most commonly available number. Yes, about 15% is wasted within the charger. But additional efficiency is lost between the power plant and your home - should we count that too? I'm being facetious with that question, but, it does help illustrate the point, no?

Regarding mpg being meaningless for a plug-in. I don't think it is, but, it depends on your perspective. My last tank was 2,013 miles, 8.41 gallons, 207.5 mpg. It is totally true that doesn't represent my total energy usage. But, it is also totally true that does accurately represent my miles driven per gallons of gasoline used. And mpg is a measure of how efficient I am being regarding my driving contributing to the world wide trade of petrochemicals. So, if Fuelly wanted to give us a way to track mpgs and continue to delay on the kwhs it would still be meaningful in a sense. The guys at Fuelly know which cars might possibly have MPG above 200 (anything that plugs in). I don't know the design of their application and database, but, perhaps they could allow plug-ins to have a higher threshold for "suspiciously high mpg."

[MMUK]

>... And mpg is a measure of how efficient I am being regarding my driving contributing to the world wide trade of petrochemicals. ...

Nope, MPG doesn't tell you that because the electricity which is not being metered is also generated from fossil fuels / petrochemicals / etc. However if you knew the combined MPGe then you would have a better idea.