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Test Drive : Toyota Prius Plug-in Hybrid Vehicle (PHV)

The Plug In Prius.

Before the Toyota Prius first arrived in California 15 years ago most people would connect the term ‘hybrid’ with the cross breeding of plants or farm animals. Now we are all used to it in reference to cars. The Toyota Prius was one of the first and now most common hybrid car, there are literally millions of them on the roads around the world.

Using an ingenious engineering design they call Hybrid Synergy Drive, Toyota have produced a car that is powered by both a petrol engine and an electric motor resulting in greatly enhanced fuel economy.
They have now taken this process a big step further by introducing the Prius PHV, a Plug in Hybrid Vehicle.

There are some minor bodywork enhancements from the original (3rd generation) Prius with one very new extra; on the opposite side of the car to the fuel filler cap is another flap covering the electrical charge socket.

Where the original Prius had a smaller capacity battery charged by a combination of the petrol engine and regenerative braking, the PHV version has a newly developed high capacity 4.4 kWh (kilowatt hour) lithium-ion unit that takes up fractionally more room than the original although to the untrained eye the interior looks identical.

In the original Prius, careful drivers could regularly achieve around 65 miles to the UK gallon. In the PHV version the claims are much higher, around 100 miles to the UK gallon. As in all cars, this is very much down to driver style, heavy right foot, lower mpg, however, hybrid drivers soon learn that a slightly gentler approach gives impressive results.

There’s only one real way to find out if Toyota’s claims are true and that’s to drive the car a few hundred miles.

When fully charged, the Prius PHV gives a very different driving experience to the original Prius. As you pull away there is no engine noise for the simple reason the engine is not doing anything. I was impressed with the acceleration under electric only drive but I was also aware that the range was fairly limited.

I make a regular 14-mile shopping trip to a nearby town and this seemed like a good first test. I zeroed the trip computer and left home with a fully charged battery. The car ran as an EV for the first 12 miles but I live on a hill above the town, it’s pretty much downhill all the way. When I pulled up in the car park I had achieved a staggering 450 UK mpg!
While I did some shopping I parked in a hotel car park that has recharge points fitted, just over an hour later I returned to the car and saw that the batteries were not full, but I had 8 miles range.

On the return journey that is mostly uphill, EV mode was disabled after 7 miles. On arriving home I noticed my fuel consumption was 238 UK mpg. Not bad for a 28 mile round trip.

On a similar cold autumn day in the original Prius I would get around 65 UK mpg on the same journey, so the increase is extraordinary.

At home I took the supplied cable from the storage unit in the rear of the Prius and plugged it into a standard 240 volt, 13 amp 3 pin socket in my garage. The battery re-charges in about 90 minutes.

The following day I tried a longer journey, 93 miles from my home into London.

Cruising at a steady 60 miles an hour along a rural road, I would regularly notice the car was running on batteries alone. The area I live in, the Cotswolds, is a tourist destination featuring pretty villages, unspoilt woodland and streams and of course many hills. In a standard petrol car we don’t take much notice of hills, we may need to change down and push the car harder but it’s not something we consider in terms of fuel use, but drive any car up a hill with your foot down and your fuel economy drops dramatically.

Likewise the Prius engine has to work harder to get up the hill with a resulting hike in fuel use, but it has an enormous advantage when it starts to descend the other side of the hill. With regenerative breaking, the electric motor instantly turns into a generator and feeds power back into the batteries. This again increases the overall fuel economy of the car, likewise with static traffic. Where most cars engines are running, using fuel while stationary in a traffic jam, the Prius stops the petrol engine running immediately, slow moving in such conditions is done entirely by electric power.

After the first 35 miles of hills, I drove on the highway all the way into London. I drove in exactly the same way I normally do, I kept at the speed limit, 70 mph with the heating and radio on. I know from driving the original Prius on the same journey I average about 65 UK mpg, i.e. I would use about one and a half gallons of gasoline to complete the 93 miles.
In the PHV when I arrived in London I had managed to get 105 UK mpg. This means the entire journey used less than one UK gallon.

I parked the car on a nearby street that has public charging posts and went to work, I parked for 2 hours in the bay, by the time I returned the batteries were full again. The short recharge time is a great advantage with on street charging. Later that night I drove back home, this time the heater, radio and lights were all on. The car is very comfortable to drive long distances; I used cruise control and simply concentrated on the road ahead and other vehicles.

When I arrived home I had covered 184 miles on motorways, major and minor roads, urban and rural roads, flat and hilly roads, my final reading was 97 UK mpg. That meant I had used just under two gallons of petrol and two battery charges. To give a comparison, a modern petrol or diesel car of similar size that manages 40 UK mpg would use over four and a half gallons to do the same journey.

But where the Prius PHV really proves it’s worth is on the far more common short journeys we make. UK government statistics suggest that the vast majority (over 90%) of car journeys are under 30 miles. On regular short trips, particularly if you charge the car at either end of the journey, it would be easy to achieve many hundreds of miles to the gallon, plus the reassurance that when the batteries do run down, the car keeps moving.

The Prius PHV is without question a big step forward for this incredible technology, it’s a delight to drive, very simple to operate and easy to re-charge. Of course the beauty of this particular car is even if you can’t re-charge it, it still works very well.