Mustang Parts
   Carrying Saleen wheels and Bullitt wheels.

Sunday, April 17, 2005

Plug-in Hybrids, Do They Make Sense?

I received an email from a proponent of plug in hybrids recently. The writer was promoting a company called CalCars, the California Cars Initiative , which has built a prototype plug-in version of the Toyota Prius, called Prius+, and is working on commercializing the upgrade.

A plug-in hybrid is an HEV which has a 110VAC connection, which can recharge the battery pack, while the vehicle is parked. With a fully charged battery pack, the PIHEV will use even less fuel than a normal hybrid, on short trips. On long trips, the battery pack will be drained and the vehicle will have to rely as much on its IC engine as a regular HEV. The CalCars Prius+ prototype was estimated at 120MPG for a 70 mile mixed city/highway trip.

The advantages to a PIHEV are that it uses less fuel for short trips, and that the electricity that is used to charge the batteries is cheaper than generating electricity on board from gasoline.

There are some disadvantages, however, which CalCars does not emphasize on their web site.

A plug-in hybrid will be even more expensive than a normal HEV, because of the larger battery packs that CalCars proposes for a PIHEV, and the added electronics to do the 110V charging. The EPRI published a report (lots of great information about HEVs) which estimated that a PIHEV with a 20 mile electric-only range would have about a $3,000 price premium over a conventional HEV. A PIHEV will also be heavier.

Another disadvantage is that a PIHEV is a step backwards, in a way, from CalCars stated goal of reducing emissions. Our grid electricity is generated mostly from burning hydrocarbon fuels--in 2000, 52% of US electricity was generated from burning Coal, 16% from natural gas, and 3% was from petroleum. Another 20% was generated from nuclear power plants (my favorite source). I don't know if the grid-to-wheels route is more efficient, in a CO2 sense.

I don't see the economics working out for PIHEVs. If a PIHEV costs $3,000 more than a comparable HEV, and an urban driver is getting an additional 70MPG, he is saving $429 a year on fuel (171 gallons @ $2.50, 12,000 mi/year), and it will take him exactly 7 years to recoup the additional cost--not counting the cost of the grid electricity. Pure electric operation costs, according to CalCars, $0.01/mi, based on off-peak discounted California electricity rates of $0.05/kWhr. If our driver drives 50% of his miles on grid charge, then he is going to be paying $60/year back for electricity, which means he will now need 8.1 years to pay back his additional investment.

I read somewhere once that the average American keeps a car for about 8 years.


Felix Kramer said...

I appreciate the AutoProphet's thoughtful comments. I urge you to read our 3-page Fact Sheet, found in PDF form at and in text form at

Here's a quick response to valid concerns Prophet raises:

* The 120MPG number is anecdotal, not yet validated on test tracks or dynamometers, for the Lithium-Ion version of PRIUS+ produced by our for-profit partnering, EnergyCS, using Lithium-Ion batteries from Valence (they supply batteries for Segways and others).The fact sheet quantifies electric costs that aren't included in 120MPG. (CalCars isn't a company, we're a non-profit group; we produced the original PRIUS+ prototype. a lead-acid battery proof of concept, and are working on a nickel-metal battery-system.)
* After 2001 and 2002 large studies, EPRI redid the numbers in 2003 (after RAV4E batteries turned out to last twice the expected 75,000 miles) and showed for the first time a lower lifetime total cost of ownership for plug-in hybrids than internal combustion or non-plug-in hybrid vehicles. (Includes lower service costs among other factors.)
* Payback depends on many variables. The biggest problem here is that society, not the driver, gets much of the payback (less imported oil, lower greenhouse gases). If you look at the driver's dollar payback for $3,000, it won't happen until gas prices are higher.
* Look at it another way: do you ask people who buy leather seats about their payback? We see these cars as offering the FEATURE of being a clean car to buyers who care about that. Hundreds of thousands of people will pay more because it makes them feel better to know they're reducing their contribution to global warming, etc. And it offers the feature of sparing drivers frequent trips to the pump: every day, if you take no more time to plug in that you do to plug in your cellphone, you leave home with a full tank. If you have a long unexpected trip, or it's not convenient to plug in one night, you're not stranded: you're driving a great 50MPG hybrid.
* Here's a quick response to that big issue: on what is called "well-to-wheel" (which ensures it's apple to apple) for many years, US Department of Energy and other studies show that an electric car is cleaner than a gasoline car even on the dirty national (50% coal) grid. For more, see section 4 of -- not a complete answer, but a start.

To keep things lively, we just added a link to this blog at

by Felix Kramer, founder, California Cars Initiative and the PRIUS+ campaign

Mxhdrm said...

Fascinating article. On the other hand, the question could be raised, why not build hybrid cars with the option to be plugged in? I’ve got a radio with a slot for batteries, an AC adaptor and a crank. People who are looking at hybrids are looking for options. Having the option to plug your car in at night outweighs the potential drawback of raising the TCO. Besides, when you look at the cars(trucks actually) on the road you begin to realize that TCO is not at the top of the list of a person who rides through town in an H2.

The Auto Prophet said...

Yes, you could build PIHEVs instead of retrofit them--but they would still be more expensive, because of the added battery capacity and charging/cooling electronics.

The Angry Engineer said...

I love the idea of hybrids, and using as much energy off the power grid as possible makes a lot of sense. With the extremely high efficiency of coal plants, there should be a net improvement in CO2 emissions over using an onboard IC engine to generate power (a modern coal plant blows-away even a turbodiesel in efficiency). And, with large domestic supplies of coal, it reduces foreign oil dependency. That's not to say I love coal, but I think it's got its place in the short term.

I'd still rather see this technology deployed first in commercial/municipal vehicles, such as garbage trucks, delivery vans, school buses, etc. Larger vehicles are theoretically burdened less with the addition of hybrid drive systems, and the type of vehicles I've mentioned engage in an extreme amount of stop-and-go usage. What GM is doing with their mass-transit buses is a big step in the right direction, I think; it's just not quite as glamorous as the Prius.

Jim Beyer said...

I disagree with the Auto Prophet on some of his points, agree with him on others.

It is rather unfair to argue the "economics" of displacing $2.50 per gallon fuel with electricity. If we factored in even 20% our $400 Billion defense budget as 'oil protection' related, then the cost of gasoline in the country would effectively double. I'm not saying this means anything to the $2.50 gallon consumer of gasoline, but I am saying that the current economics of gasoline in this country is not exactly fair, and in the long run, probably not sustainable. Given this, PHEVs probably deserve a careful look.

I also think the price of batteries, etc. has a lot of downward price potential on it. If only due peripherally to the 42 volt changeover that suppliers are beginning to address. So I see downward pressure on battery prices and upward pressure on gasoline prices. This leads to the notion that the economics for PHEVs are likely to improve over time, not worsen.

But I agree PHEVs charged with coal-fired electrcity does not make a lot of sense. You can argue +/- 20% CO2 emissions, but that really isn't enough to justify this effort. Plus no one likes the mercury and radioactive trace particles coming out of coal-fired power plants.

I think benefit is a little subtler. Renewable electric (sun and wind, mostly wind) is more expensive than grid electricity (call it 10 or even 20 cents/kwh) but it is still cheaper than the gasoline it would displace if used to power PHEVs. (If a gas engine is 30% efficient, it only makes use of about 10 kwh of the 35 kwh in a gallon of gasoline.) Plus there is the economic benefit of spending money here in the US for the energy rather than sending it abroad.

Renewable electric is also intermittent, which makes for a hard sell on the grid (because energy suppliers can't easily assess their baseload potential) but a perfect fit for PHEV recharging. If a PHEV spends 20 hours per day plugged in, that's a broad timeframe to accomplish a 4-6 hour recharge. That's an intermittent DEMAND that utilities could use to level their intermittent generation peaks.

I think anything that could reduce our oil needs by tens of percentage points is really worth looking at.

If it was available as an option to certain hybrid models, an automaker could field a PHEV without incurring the support costs of an entirely new car.