My car broke down and repairs cost more than it’s worth. Time for a different one. I’ll likely get a Honda Civic or Toyota Prius. Do fuel savings from Prius justify price premium? No. It would take at least 8 years to reach breakeven between the two at current gas prices. I may buy a Prius anyway, but for other reasons.

Here’s the calculation (I ignore resale value, since I tend to drive cars to end of life).

I will buy used. I found these two options:
2012 Prius Two 51city/48highway $18,600 40k miles (Edmunds.com)
2012 Honda Civic: 29city/41highway $15,000 39k miles (Edmunds.com)

I probably drive 75% of time in city and 25% of time on highway. This gives following mpg:
Prius = 0.75*51 + 0.25*48 ~= 50.25 mpg
Civic = 0.75*29 + 0.25*41 ~= 32 mpg

I averaged ~10,000 miles/year in the broke-down car. Each car would consume following fuel:
Prius = (10,000 miles/year) / 50.25 mpg = 199 gallons
Civic = (10,000 miles/year) / 32 mpg = 313 gallons

In California, taxes and fees would add ~10% to list price, giving following out-the-door price:
Prius = $18,600 * 1.1 ~= $20,500
Civic = $15,000 * 1.1 = $16,500

The premium for a Prius is $20,500 – $16,500 = $4,000. A Prius consumes 313 – 199 = 114 gallons less gas per year.

With fuel price (F) and years driven (Y), we can calculate the breakeven point:
$4,000 = 114 gallons * F * Y
Y = $4,000/(114 * F)

If F = $4.20/gallon (current price), Y = 8.4 years.
If F=$7/gallon, Y = 5 years

I consider 5 years the acceptable payback period to buy the technology based on fuel savings alone. As you can see, gas prices would have to increase to $7/gallon to make that happen.

Considered another way, what is the likely premium paid to own a Prius over 5 years over a Civic:
Premium = $4,000 – 114 gallons * $4.20/gallon * 5 = $1,600

There are a lot of reasons to buy a Prius, but for me money saved on fuel is not one of them.

Found here.

I only heard about this counterpart to Moore’s law recently (Eroom is Moore spelled backwards). Drug development has become more expensive at a relatively constant rate over time. Dollars are adjusted for inflation.

These rules only apply to entities licensed through the USA.

1. Google Maps often doesn’t use satellite images over cities. It often uses images taken from airborne platforms (Wikipedia):
“Although Google uses the word satellite, most of the high-resolution imagery of cities is aerial photography taken from aircraft flying at 800 feet (240 m) to 1,500 feet (460 m); however, most of the other imagery is from satellites.”

2. There are legal limits on what image resolution can be marketed commercially (book):
Ground sample distance (GSD) of 0.5 meters can be marketed generally by USA-authorized entities. GSD greater than 0.25 meters requires special permision.

3. Commercial entities can only take low-resolution space-based images of Israel (NOAA):
No USA entity can distribute high-resolution satellite photos of Israel. According to the Kyl-Bingaman Amendment requires “department or agency of the United States may issue a license for the collection or dissemination by a non-Federal entity of satellite imagery with respect to Israel only if such imagery is no more detailed or precise than satellite imagery of Israel that is available from commercial sources.”

Funny even if you don’t know the trail…

Here

His claims of useful energy conversion efficiency:
40% fancy solar cell for spacecraft
35% fossil fuel power plant
28% all electric car (80% battery * 35% power plant)
15-25% human metabolism
15-25% burning gasoline for locomotive power
15% mass-market polycrystalline solar cell
5% photosynthesis

He claims 15% efficiency of solar panels is pretty good. I agree.

A professor at the University of Utah has ~5 minute lecture videos for various EM topics. They are great.

Here are some of my favorites:
Impedance matching
Intro to stub matching