Monday, November 28, 2005

Should you get a Prius?

A friend recently asked me if I thought he should lease a Prius for a few years. I wrote a detailed email back to him and he made the suggestion that I post the answer here on my blog for others to read... so here goes!

It really depends upon your objective -- are you interested in good gas mileage? are you interested in reducing greenhouse gas emissions?

The Prius really isn't the best at any of these. I think the only thing the Prius DOES have going for it is that it is universally associated with the idea of hybrids and thus, by extension, with environment friendliness...

The basic problem with hybrids today is that it is a closed loop -- the gas engine recharges the batteries. So in general terms total energy efficiency is necessarily lower than if you just burned the gas straight away -- that is, there is necessary energy loss in the storage and reuse... So the entire "efficiency" of hybrids comes at one place - the stoplight. Gas vehicles burn away gas at the stoplight without any gain. Hybrids shut off the motor altogether, thus "saving" the energy otherwise lost at stoplights. So if you do a lot of stop and go city driving, a Hybrid could save gas and reduce pollutants... Now, if Hybrid manufacturers allowed you to plug the car into the grid at night you could avoid using gas to recharge the batteries (at least for short trips)... but for marketing reasons they won't do this -- consumers in their view are fearful of having to plug in their cars...

But if you do a lot of freeway driving, you have better options. Check:

First look at Hybrids from Toyota vs. Honda:

Toyota Prius:
City: 60 Hwy: 51 Tons of greenhouse gases/yr: 3.50

Honda Insight (Manual) Hybrid:
City: 60 Hwy: 66 Tons of greenhouse gases/yr: 3.10
*The insight does better in Hwy driving due to its aerodynamic design. You choose a manual transmission over an automatic because it weighs significantly less...

But then compare to the diesel VW Golf:
City: 38 Hwy: 46 Tons of greenhouse gases/yr: 5.2
The reason that Hwy is better than city here, as with most cars, is that the city driving MPG is hurt by all of that stop and go driving.

One thing that the "greenhouse gas" calculation on the US Gov website does not take into consideration is that diesel produces a different mix of gases than burning gasoline -- but leave that aside for the moment and look at the greenhouse gas number though in the context of using biodiesel instead of gas:

While Nitrous Oxide increases by about 10% at 100% biodiesel, the key greenhouse gases - CO and HC are reduced by 50% and 70% respectively - far outweighing the increased fuel efficiency of gas-hybrid cars.

What we really need is a biodiesel-hybrid car that you can plug into the grid... OK what we really need is hydrogen cars with personal refueling stations powered by rooftop solar energy...

In the meantime though, your best bet for gas is a manual transmission Honda Insight. Best bet for reducing greenhouse gases (and dependency on the middle east) is a VW Golf Diesel.

Lest you think that finding biodiesel is hard, here is a guide to finding a refueling station in the bay area:

OK... only three stations right now... but its growing! :-)

Here is a nationwide map:

You might also be interested in this new book, Biodiesel America: How to Achieve Energy Security, Free America from Middle-East Oil Dependence and Make Money Growing Fuel,283,0,0,1,0

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