I'm not a current EV owner, I've got a Corolla. I'm not rolling through stop signs or anything but I do try to maximize my fuel economy whenever I can. I use cruise control often, if I know the lights going to turn red I'll start coasting as far out as I can, I don't accelerate too fast or brake too hard (if I can help it). My question is how many of those things transfer to EVs? I know the coasting will for the regen braking, but what about the others? Are there completely different things you can do?
Your questions are good ones
@dsvick. The core answer is that whether you drive aggressively or in hyper-mile mode, your energy efficiency per mile will be dramatically better in an EV than your Corolla (or any other car that gets a significant fraction of it's energy from burning fossil fuels). As an order of magnitude approximation, the Roadster is a roughly 120 mgpe car (older EPA test applied when Roadster was released). That's a little under 250 wh/mile. When I drive my Roadster really aggressively (non-winter conditions), I might be able to push that down to 90 mpge. And if I drive really light footedly and more importantly, consistently (no micro accelerations and decelerations - cruise control is good for that), then I can readily hit the EPA rating, and a bit more if I'm willing to drive 40 instead of 55 (mostly not
).
(Read about mpge
here - it's intended to provide a means of directly comparing efficiency between vehicles using different power sources)
Coasting is different in a Roadster or Model S, and there is arguably a few basis points of improved efficiency available by using actual coasting over regenerative braking. It's manually available in the roadster (shift from D to N, then back to D to reenable regen or go back to supplying power - I never hassle with it). Over 200 miles of driving, the level of significance of the activity is unlikely to rise up to even a single saved kwh.
The order of magnitude different between coasting in a gas engine car without regen, and coasting in an electric car with regen, makes the activity important for efficiency in one, and a colossal use of mental energy with little actual saved energy in the other. It's just different.
Maximizing you efficiency in an EV really does simplify down to these major choices:
- gentle acceleration over hard acceleration. The difference in improved efficiency is much less dramatic in the EV over the gas car, but it's present and noticeable.
- set cruise control to 55 on the highway
- let regen bring you all the way down to 10 mph. 5 mph for extra points. Surprisingly easy to learn to do as well - took me less than 2 weeks to get it mostly right all the time.
- And if you do need to brake, let the regen do as much as it can (more energy regenned at higher speeds than lower speeds), then use the brakes for the last 10/20/30mph reduction.
- If you wanna get crazy about it, draft a truck on the highway - it's air resistance from 55 or so up as your primary energy consumer, so drafting will help.
Peak efficiency in the EV is around 20 mph, and best tradeoff between time and distance is around 40 mph. Rated ranges are based on 55 mph driving, and efficiency falls off fast above that. But "fast" is still different from a gas car. Somewhere in the 80 or 90 mph range, you didn't get the engine tuned for peak efficiency around 65 (gas car), and now everybody's efficiency is suffering badly from air resistance. Now you're driving a car with 1.5 gallons of gas equivalent (Roadster, Model S is closer to 2.5) and range is really suffering
(Lovely side effect - I get my rated range in stop and go driving where I'm just following the traffic around me; it's higher speed highway driving where I stop getting rated range).
This is all a function of the motors in the two kinds of cars. They behave differently, with different power curves and different efficiency curves. The electric motor is so highly efficient to start with (80-90% instead of 20-30%, order of magnitude), there isn't as much room to play with getting things just right.
The best part of the whole deal with the EV, is that you can get the same efficiency out of the car whether it's in Performance or Eco mode. It doesn't change the conversion of energy into motion, as it does with a gas engine. It doesn't turn off one or more cylinders in the engine, or other crazy optimizations like that. So you can drive in an efficiency minded manner most or all of the time, and STILL have sudden zip available if you want or need it.
