The 100 MPG Toyota Prius Plug-in Hybrid

Hybrid cars will get even better gas mileage when they become plug-in hybrid-electric vehicles.

Plug-in Prius Hybrid

Prototype of the plug-in hybrid Toyota Prius.


Content Tools

On the outside, the Toyota Prius I’m driving looks about the same as any Prius you’d see on any given day. Aside from the auto-show graphics on the body, the only hint of something unusual on this Prius is the second fuel door on the rear flank of the passenger side. Pop it open and instead of a gas cap, there’s an electrical outlet. This particular Prius is more than just a gasoline-electric hybrid — it’s a plug-in hybrid. The one I’m driving is one of several that Toyota is using to test this promising and advanced technology.

A plug-in hybrid runs solely on electric power for longer periods than a typical hybrid, thanks to extra batteries. And like a typical hybrid, a plug-in taps the gasoline-electric hybrid powertrain when driving distances exceed the electric-only range. Toyota is currently testing a small fleet of plug-in Prius that have an all-electric range of seven miles. Seven miles may not sound like much, but it’s enough for short commutes or errands. While driving on that electric power, a plug-in Prius can achieve the fuel economy equivalent of 100 miles per gallon or more. A conventional Prius gets about 48 mpg in city driving.

More Batteries and a Power Cord

Toyota’s Hybrid Synergy Drive system allows its hybrid vehicles to operate on electric power (via batteries and an electric motor), gasoline power (via a small internal combustion engine) or a combination of the two when both are needed. The plug-in version has a second nickel-metal hydride battery pack, which powers the extended electric range unique to the plug-in. The additional batteries fit where the spare tire normally goes. Additionally, Toyota revised the hybrid system’s computer controls to allow the plug-in to operate on all-electric power longer and at higher speeds than in a conventional Prius.

When it’s time to recharge, a simple power cord is connected to the Prius and plugged into a standard 110-volt outlet (the kind we all have in our homes and garages). A full charge will require three to four hours, or just 1 to 1.5 hours if a 220-volt outlet is available.

Power outlets at offices and in parking garages would allow plug-in hybrid drivers to top-off their vehicles while they are at work, thereby doubling the daily all-electric range of the vehicles. If you live close enough to where you work, you might never need gas.

Plug-in Progress

Toyota is testing prototypes of the plug-in Prius in the United States, Japan and France. Additional studies are underway at the University of California at Irvine and at the University of California at Berkeley. These programs are charged with researching consumer expectations of plug-in hybrids. The goal is to determine the sweet spot in the mix of cost, electric range, battery size and charging time to make the best plug-in Prius possible.

Currently, battery price is a major obstacle. Toyota says that plug-in batteries demand $500 for every mile of electric range. So the prototype plug-in’s seven-mile range adds $3,500 to the manufacturing costs of a Prius. (The sticker price of a brand-new Prius is $22,720.)

Will people be willing to pay that much more for the improved gas mileage? Would people pay an extra $5,000 for a 10-mile all-electric range? Only time and the market will tell. Furthermore, the $500 figure goes with nickel-metal hydride batteries, not the more advanced, powerful and expensive lithium-ion batteries regarded by many as the battery of choice for future plug-in hybrids and electric vehicles. Toyota is developing its own advanced battery technology through a joint venture with Panasonic EV Energy Co. The hope is to create something even better than lithium-ion and find breakthroughs and economies of scale that will significantly reduce prices in the future.

Plug-in Hybrid Conversions

If you want a plug-in hybrid before the automakers produce them, it is possible to convert an existing hybrid to a plug-in. There are several third-party companies, such as Hybrids Plus and Hymotion, that do conversions of the Prius and Ford Escape Hybrid. For a longer list of conversion companies, click here. Some of these conversions perform quite well, but they are expensive: Prices range from $6,000 to $30,000 or more, depending on the vehicle and the type of battery. Note that converting your hybrid will void all warranties the automaker provides for the vehicle.

The Plug-in Prius, Driven

My drive of the plug-in Prius was enlightening. The car was very driver-friendly and I found it easy to operate in all-electric mode. I drove in urban conditions in Detroit. Other than the lack of noise and vibration from the gas engine, the only unusual sensation was a Jetsons-like whir as the car accelerated. With the changes to the computer controls, I could accelerate to 62 mph on pure electric drive, whereas the regular Prius will start the internal combustion engine at about 20 mph. Merging onto the freeway at 60 mph propelled by just the electric motor is a strange feeling, but it is possible to maintain that speed without starting the gasoline engine. I tried a few hard acceleration runs to feel the transition from electric to gas-electric and back. It’s not transparent, but perfectly acceptable.

The Plug-ins are Coming

Toyota isn’t alone in its experiments with plug-in hybrid technology. Ford, GM, Volkswagen and other automakers big and small have plug-in hybrids in the works. The highly anticipated Chevrolet Volt can plug in to recharge, but unlike hybrids or plug-in hybrids, it is propelled strictly by electric drive. The small gas engine is used to recharge the batteries when the electric motor needs more juice.

Consumer demand for significantly better gas mileage is clearly here, making plug-in hybrids a viable product. It may take several years to work out the details and challenges, but the power to plug in will eventually be in our hands.

10/9/2008 2:04:04 AM

that certainly hits on a major point of our penny wise, pound foolish society. purchasing an expensive environmentally intensive manufactured (and eventual disposal) vehicle. As these cars age they will lose power and MPG as the batteries deteriorate, and it's very unlikely that those in the market for second and third hand cars will be financially willing or able to spend several thousands of dollars on top of the cost of the car to replace batteries and other components. Yes, they will be a great boon to the upwardly mobile, who can spend lavishly, throw away the undesirable and feel good that they are somehow saving the planet, but for those of us that no longer march in the consumer parade and look farther down the road to see what happens where the parade disperses, costs and what's left to clean up, these might well wind up being albatrosses that are no better than that old mini-van, but with much less room and carrying around hundreds of pounds of dead batteries.

teresa holler_1
10/6/2008 1:09:58 PM

Wouldn't it be great if we all had wind or solar powered homes to plug these rechargeable hybrids into? The time has certainly come. Legislators could make this technology affordable if they chose to. All we need to do is front the trillions of dollars that will be saved by averting environmentally mediated diseases in the near future and use it for this technology! The quality of our environment is directly linked to the quality of our health. It is time to Stop Treating! Start Preventing! Teresa Holler

10/5/2008 9:35:02 AM

I've found elsewhere that the vehicle will use about 0.25kWh per mile. So I calculated the cost per mile like so (which makes more sense the me than mpg). Lumina (L) miles per unit = 23 (gasoline) Prius (P) miles per unit = 4 (electric, 1 mile / 0.25kWh) L: 1 unit / 23 miles = 0.0435 units/mile P: 1 unit / 4 miles = 0.25 units/mile L: 0.0435 u/m * $3.00 / unit = $0.1305 / mile P: 0.25 u/m * $0.1635 / unit = $0.0409 / mile 7 mile trip L: $0.9135 P: $0.2863 100 miles driven (aggregate, short daily commutes) L: $13.05 P: $04.09 These figures look a lot different when you play with the numbers. With a 35mpg car, it only costs half as much per mile (instead of 3 times). But with $4/gallon gas, the cost for the same vehicle gets close to 3 times as much again. With cheaper utilities, say $0.10 kWh, the Prius only costs $2.50 for a 100 mile trip, making it over 5 times less costly as the $3/gallon / 23mpg Lumina, and about 7 times less costly with $4/gallon gas. I don't think very many new electric or hybrid make any sense from a narrow focused pure cost perspective anyways. They don't make up for the cost difference in gas savings in the long run (though that doesn't factor reliability and maintenance cost). But when compared to what it would cost to make great environmental and social changes without them, they're a steal.

10/4/2008 12:42:57 AM

correction, .4921 x 23 is $11.32 in the second paragraph, I mistakenly multiplied by 21

10/4/2008 12:38:15 AM

Most people do think in terms of MPG only with no regard to where the rest of this "free fuel" is coming from. If I am to assume from this story it takes about a kilowatt of electricity to travel a mile (15 amps X 120 volts for 4 hours = 7.2 kilowatt hours of electricity giving the ability to travel 7 miles ), this would be no bargain for me. Our current electric rate where I live is 16.38 cents for the first 500 kWh. If I compared this to my '91 Lumina APV minivan (which gets 23 MPG in the winter with studded snow tires), the cost of driving the plug in hybrid only 7 miles (before the gasoline would kick in) would equal $3.77 a gallon (.1638 X 23), and that of course is also assuming no use of lights, heater or any other energy consuming element. If it wasn't for a cost equalisation programme (funded by oil royalties in our state for rural communities), or if I consumed more than 500 kWh, the rate here would be over 49 cents a kWh (this rate also applies to non-residential customers), that would make that gallon of "hybrid gas" costing $10.33 (.4921 X 23) Yes, not everyone is paying 17 cents per Kwh (although that is this May's average for the north-eastern states according to the DOE, so it's certainly not a far-fetched fantasy). What happens in the future as more power plants need to be constructed or road taxes are shifted to offset the loss of gasoline sales? One thing corporate america should have taught us, levels of income or profits and growth will be maintained at all costs

10/3/2008 4:41:41 PM

when you say 100mpg but it plugs in. how is the cost of the electricity from the grid factor into this?