Now for what the EPA numbers actually means for the Model S, other BEVs and PHEVs.
For BEVs and PHEVs, the MPGe and kWh/100 mile efficiency numbers come from plug-to-wheel. This means the EPA actually measures the electricity taken from the socket, not just the electricity from the battery. Basically the procedure is to have a fully charged car, drive it in the EPA tests, then recharge the car to full again and measure the electricity used. You can see the details in this FOIA request done for the Leaf:
http://www.mynissanleaf.com/viewtopic.php?f=4&t=2433
What this means is you can't really figure out the range of the car directly from the efficiency numbers even if you know the battery capacity of the car (56kWh for the Roadster). You have to know the amount of electricity it takes to
charge the car from the socket (about 60-70kWh for the Roadster).
Another thing to know is that the new EPA stickers that show the range of BEVs didn't come out until the 2011 model year.
New sticker (after 2011):
Old Sticker (before 2011):
So before the 2011-2012 time-frame, pretty much anything went in terms of the
advertised range of EVs.
Even today there is really no set requirement for what kind of cycle you use to advertise the range of an EV (kind of like how automakers can choose to use the highway mpg of a car in advertising). However, with the new car sticker actually saying the range explicitly, it becomes harder to use a different number and get away with it.
Like EVNow mentioned, the 100 mile number advertised for the Leaf is from the LA4/UDDS cycle. After the sticker came out, everyone basically took the 73 mile number in the sticker (which represents the range in the combined cycle) as the official number. The combined cycle is basically 55% city and 45% highway.
Anyways, from a previous post, the 73 mile number is from multiplying the test results from an EPA 2-cycle test by 70%. They used 76% for the Volt.
From the FOIA request by Smidge204 over at the Leaf forums, the EPA conversion factor between "2 cycle" and "derived 5 cycle" is 70% or higher.
Leaf: 141.69 MPGe (actual test) x 70% = 99 MPGe (sticker)
Volt: 48.44 mpg (actual test) x 76% = 37 mpg (sticker)
http://www.mynissanleaf.com/viewtopic.php?f=4&t=2433
Anyways I worked out these range numbers based on the above information (EPA2 = EPA combined 2-cycle; NEDC ; EPA5 = EPA combined 5-cycle):
2011 Tesla Roadster:
EPA2 - 245 miles
NEDC - 211.3 miles (340 km)
EPA5 - 176 miles (53kWh / (30kWh/100 mile))
2011 Nissan Leaf:
EPA2 - 104.3 miles (73 miles / 70%)
NEDC - 109 miles (175 km)
EPA5 - 73 miles
2011 Chevrolet Volt:
EPA2 - 46.1 miles (35 miles / 76%)
NEDC - 56.1 miles (83 km, Opel Ampera)
EPA5 - 35 miles
I also show the different amount of combined range for the different test cycles in that post.
One thing you should notice is that the EPA 2-cycle number for the Roadster is actually
245 miles. But remember how I said stickers for cars that came after 2008 reflected EPA 5-cycle test? Well, apparently that doesn't apply to the Roadster's range number, which still from the 2-cycle test. However, it does appear the
30 kWh/100miles number is from the 5 cycle test (245 miles * 70% = 172 miles, which matches well with the number range number I came up with working from the kWh/100mi number). I suppose this anomaly is from the fact that the Roadster came out before the new stickers came out and during the transitional period between the 2-cycle and 5-cycle tests.
Now on to the
55mph range. The 55mph came up from the following graph for the Roadster:
http://www.teslamotors.com/blog/roadster-efficiency-and-range
Notice that at 55mph, the range for the Roadster is basically
245 miles. This is basically exactly the same as the EPA 2-cycle range. So basically you can expect the 2-cycle range to be the same as the range when traveling at a steady 55mph.