Solar Powered Roof?

Just not one that is measurable.

 

I know this is simplifying it a lot, but I believe the argument still gets the point across:

I just checked out all of my data I took for the entire summer of one very specific trip (which was round trip, so no elevation change, and taken every day sometimes several times per day).

- With the tank 80% full or above I got an average of 70.5 mpg. (assuming 10.7 gallons average=65 lbs.)
- With the tank 30% full or less I got an average of 72.4 mpg. (assuming 1.8 gallons average=11 lbs.)

-This comes out to be a difference of 1.9 mpg for every 54 lbs. (fwiw I believe this figure to be just a bit higher than what more tests would/should be)

But I think it is very safe to say that 66 extra lbs on the vehicle will at least drop your FE by 1 mpg.

 

Your anecdotal evidence is countered by other anecdotal evidence here on PriusChat. Some of the leading hyper milers have the solar roof.

But the fact that there's no rating difference from Toyota is more substantial. Is the car going to get measurably worse mileage with a 140# owner vs. a 200# owner?

 

Who knows what the differences are between different Honda Fit models. In the case of The Prius solar roof the weight difference is so negligible as that of a large dog or small child, well below the basis "as tested" loads, as to be meaningless.

 

What weight amount would you estimate would go over meaningless? And what is your definition of meaningless in this regard?

 

Ah...well we know that larger tires have big impact on mileage. And Honda feels the body kit affecting aerodynamics also has significant impact on mileage.

Not so the sun roof on the Prius which has no documented or anecdotal effect on mpg.

Guess we'll have to keep adding weight to find out. So far we have a good idea that the sun roof weight difference has no documented effect.

 

Haha, whatever you say man.

 

On the Toyota website, the Tacoma regular cab, access cab, and double cab equipped with the same base drive train have identical EPA ratings of 19/24 yet the double cab is wider, taller, longer, with larger wheels/tires and weighs 400lbs more! Me thinks this is an EPA loophole.

OP, yes the solar roof works well. It's a shame Toyota isn't offering it on other models.

 

Exactly. I highly doubt car companies submit every single variation for testing to the EPA.

 

I offer no anecdotal evidence or subjective opinion: just the facts ma’am.

MOST new cars and trucks in the US are NOT TESTED by the EPA's National Vehicles and Fuel Emissions Laboratory in Ann Arbor, MI. (What do you expect for $9 billion?) Fuel economy testing is conducted by the vehicle manufacturers themselves: frequently with pre-production prototypes in accordance with standardized test protocol specified by federal law. Automakers then report those numbers to the EPA. Only 10-to-15 percent of all new models are actually RE-TESTED by the EPA to validate the automakers' numbers and help keep automakers honest. (Obviously this didn’t happen with Hyundai-Kia for those following automotive news. This is incidentally the second time the Koreans have been caught “cooking the books”)

Manufacturers are NOT REQUIRED to test EVERY vehicle variant offered for sale. They are only required to test ONE representative vehicle for each combination of loaded vehicle weight class, transmission class, and basic engine. This means that a carmaker would only be required to separately test a particular build variant if the added mass of equipment pushed the car into the next EPA weight class, or the variant had a different engine or transmission.

According to EPA protocol; the vehicle manufacturers’ test the vehicle’s aerodynamic drag, rolling drag, and inertia on a test track to calculate three coefficients employed on a chassis dynamometer to replicate major forces acting on the car. The vehicle is placed on a dyno in a lab using a professional driver and put through a series of cycle tests that increase load based on speed, acceleration, and incline to simulate "typical" trips that represent five different drives: city, highway, high speed, air conditioner and cold temperature. For vehicles using carbon-based fuels (e.g., gasoline, diesel, natural gas, etc.), a hose is connected to the tailpipe to collect the engine exhaust during the tests. The carbon in the exhaust is measured to calculate the amount of fuel burned during the test. (There are unique criteria established for electric vehicles and plug-in hybrids that are slightly different.)

There are normally occurring production variances and tolerances in cars that result in sample differences in internal engine friction and chassis rolling resistance. The car maker’s objective is to hand pick a “lab queen” for the EPA tests that is properly broken in and has the most basic equipment (the lightest weight), while still representative of the model, and a gifted professional driver for the test cycles on the dyno.

There is absolutely no rational reason or legal mandate for Toyota or any carmaker to test their heaviest model variants. It would only serve to damage their market competitive position in the face of competitors motivated to play the same game.

Every ounce you take out of a car improves the vehicle's performance and fuel economy. This is why carmakers are rushing headlong into lightweight materials such as high-strength steel, aluminum and carbon fiber. The EPA estimates that for every 100 pounds taken out of a vehicle, the fuel economy is increased by 1-2 percent. The converse is also true.

Whether a weight delta comes in the form of added equipment such as solar roof or the driver’s belly fat is inconsequential to physical laws in play. Yes; the more your butt weighs the less your fuel economy will be.

 

This.

 

Now Proxy is silent...coincidence?

 

But none related to any impact a 60# heavier driver would affect the mileage of Prius.

There is no evidence, anecdotal or documented that the additional weight for the solar roof has any measurable effect on Prius mileage.

 

Gas Mileage Tips - Driving More Efficiently

Go down to the part of the page where it says "Remove Excess Weight"

Does the solar roof weigh extra? Does weight affect FE?

This really isn't rocket science man. In fact, I would guess the average high school student could understand this concept.

 

No appreciable weight difference or performance difference per anecdotal or documented specs.

You are going to need facts not generalities and the facts are against you regarding any known effect of solar/sun roof on mileage. Greatest effect is likely aerodynamic effect when open but that is also hard to document.

 

66 pounds (2% of the vehicle's weight) is not appreciable to you? If not, what is the weight amount that becomes appreciable to you?

 

Not appreciable to any of the mileage anecdotal evidence on PriusChat as many of the top hyper milers drive Prius with sun roofs, not appreciable to any documented evidence as nothing from Toyota or documented anywhere of any mileage lost with sun roof.