That's a worse slogan though. Compare "Now with 10% more efficient windshield wipers!" and "Now with 10% dimmer screens!"

Usually when it’s raining there isn’t much need to run the display at full brightness. It’s largely a wash.

Why not dim the screen _and_ have more efficient wipers? ;)

"It’s largely a wash."

I see what you did there.

Hm, even LED TVs use something like 30W, don’t think you’d get much out of dimming a tablet sized screen.

50W for 5 hours is 250Wh, which is a mile extra range. That’s worth having.

What’s funny is all of these trade offs have always applied to ICE cars as well, but for some reason no one cares. Blasting your radio shortens your range even in a gas vehicle. Running your wipers shortens your range even in a gas car.

The range of an ICE car is not as big of a concern as with EVs, giving that they already have a substantial range, "recharging" is quick, and fuels are very energy-dense.

I'm not much for electronics. Can you explain how playing the stereo affects mileage?

Additional power draw on the accessory circuit places increased load on the alternator which in turn causes the engine to run a little harder than it otherwise would. Thus burning a little extra fuel.

Cheers, alternators are essentially magic to me. Id have presumed they were generating 'enough' power at all times the engine was running.

They produce based on current draw, but have a maximum output, usually around 60-85a for and older car, to 120-240a at 14.4vdc for a newer car or truck. There is no permanant magnet, so the coils require power to generate power. Its quite interesting.

Further to this the 12V battery effectively acts as a big capacitor while the car is running, to smooth out the power that is available.

I found this out the hard way a couple of years ago. My 12V was dead, yet I managed to jump start the car and get it running. I thought it would be ok to drive to get a new battery, as long as I kept the engine running high enough. After a couple of km the dashboard lights started to dim, so I tried reving it as high as I could, but the battery wasn't able to buffer the power and supply the ignition system, so the engine stopped. It was rush hour and I was in the middle lane, so it wasn't a particularly fun wait for the tow truck.

In the old days of lower power alternators (or really old days of generators), and lower power engines, the revs would drop noticeably, and the note change, when you turned dip lights on, aircon or even occasionally - in smaller cars - the heated rear demister! Made it very obvious the engine was working harder.

Now that tickover and fuel injection is computer controlled or we have EVs, and there's a far heavier electrical load in all cars all the time, you never notice any more. They all take power, and decrease fuel efficiency.

"some reason" being you can just add an extra liter to the fuel tank, not the case for batteries.

Tesla's speaker system is 200/560W. So it's possible to get to 50W just from screen and speaker savings. And that's assuming constant worse case use of the wipers: high speed and full load like you're driving through a waterfall. Pulling up a spec sheet for a wiper motor, it looks like normal load is only supposed to draw ~6-10W.

On the other hand even a 1 mile (probably less) saving over a 5 hour (~200-250mi) trip through the rain might as well be a rounding error regardless of the fuel used. Many other methods for achieving the same saving are not as flashy though.

I imagine the most important way is to ensure optimal tire pressure at all times. Many people tend to ignore this even when having pressure sensors at hand which leads to a whole lot of wasted fuel.

The reason wipers only received minor optimizations over the decades is because they work well, are cheap and enviably reliable. So any new wiper system design has a high bar to pass, beyond using new tech.

This sort of thing is why I refer to "the noise floor" in these sorts of discussions. It's not that it's untrue that it may save a mile of range, it's just so dominated by other factors that it doesn't matter. Your human cognitive spotlight is focusing on this one fact, and it may be "true", but that doesn't make it important. It's not worth engineering effort to save amounts of power that will be casually wiped away by any number of little things.

(Sometimes you can bind together several little things into one big one worth doing, but human intuition is still often broken by the factors of magnitude involved. 6 %.0002 things still don't add up to anything significant, for insurance, even if it may feel like six things ought to matter.)

> 50W for 5 hours is 250Wh, which is a mile extra range. That’s worth having.

That represents about 0.5% of a Tesla's advertised range.

You do 10 of these things and you have 5% better range, more than your competitor who ignores 0.5% savings.

Calling it 0.5% is generous.

* Only when it rains. (It's worthless the rest of the time)

* Only if all of the motor power is saved. (Presumably the new mechanism uses some power)

* Only if the motor is running at full power the entire time it rains (even on "high" this is not true).

* Only if range is not otherwise impacted by the rain (nope).

If it rains all the time, and the above are all true-- yes, it's worth 0.5%.

While I agree with you and am excited for whatever improvements can be made, I think the most likely retort to this argument is "While you're worrying about 10 0.5% savings, your competitor is focusing on optimizing things that actually matter."