As its launch date approaches, both verifiable and speculative reports are circulating about the Toyota Prius Plug-in Hybrid.

Among them are that it is expected to return a standard-Prius-beating 107 MPGe, cut CO2 emissions from 89 g/km to 49 g/km, and will debut September 13 at the Frankfurt auto show.

In response to our inquiry, Toyota told us that the 2012 Prius plug-in will indeed be first presented at Frankfurt. The company is keeping a lid on other info, but we’ll tell you more of what the reports are saying just the same.

2010 Prius Plug-in Hybrid at the EDTA conference in Washington in April.

First off, the outstanding fuel economy and emissions efficiency reports appear to be correct. They are based on the car's reportedly having gone through a UK drive cycle. In it, the Prius plug-in achieved a 128-mpg rating, which is being equated to 107 MPGe for the U.S.

Toyota was quick to qualify this report however.

“That number is based on a virtual test cycle,” said Toyota’s Amy K. Taylor in an email, apparently not wanting to over promise and under deliver. “We expect the number to vary in real world driving conditions.”

Like the standard Prius, the plug-in will use a 1.8-liter, 134-horsepower engine and a 60-kilowatt electric motor, with the addition of on-board charger for the battery.

The distance it can travel at speeds up to 60 mph remains a mystery.

Another improvement over the standard Prius – as well as the 2010 demonstration version (in photos) – is the 2012 production plug-in car’s battery is believed to offer slightly higher output to enable around 15 miles of all-electric range. This is up a wee bit from an estimated 13 miles – and remember it could even be higher, and we probably won't know for another month.

Rumor has it that the 2012 Prius Plug-in's battery could be as large as 5.2 kWh.

Taylor said the 2010 demonstration version had a 3-kWh battery, and all-electric speed of 60 mph, but of the 2012 version, said only, “Product details have not been announced regarding the production vehicle.”

Since Taylor did not deny an improved battery, it remains possible a more powerful, maybe even more compact battery pack will come with the 2012 plug-in Prius.

Recharge time from 120-volt house current for its battery – that could be around one-fifth to one-third the size of the Chevrolet Volt's battery – is for now still estimated at around 90 minutes.

One difference between Toyota’s thinking and General Motors' approach to the Volt with its 16-kWh battery is that by giving the Prius plug-in a smaller, lighter, less expensive battery, it yields a lighter car with lower selling price.

Gas 2.0 and others report Toyota expects to sell 17,000 units for 2012, and estimated a U.S. price at around $26,000-$32,000 before incentives.

Here too, Toyota declined to verify the eager speculation abounding on the plug-in version of this most popular hybrid.

“We have not made any announcement regarding production plans,” Taylor said. “Pricing will be announced closer to on sale date.”

The Prius plug-in is due to go on sale in the U.S. in the spring of 2012, Taylor said.

She could not confirm if or when the Prius plug-in would be made available in other parts of the world.

"I'm not aware of the launching timing for other markets or if it has been announced yet," Taylor said.

Since its introduction, the standard Prius, now in a third-generation version, has grown steadily to a high degree of popularity among alternative technology vehicles.

Plugged in at the Renaissance Marriott across the street from the EDTA conference in Washington: a prime spot reserved for a prime customer.

The cars are imported from Japan where the U.S. is largely blocked from competing on an even footing due to tariffs and alleged trade inequity.

Further, when factoring all the economic advantages a plug-in Prius will provide, it may be worth considering the ships required to transport the Prius use an enormous amount of bunker fuel – as much as 120 gallons per mile.

One very rough estimate put the consumption of bunker fuel needed to import approximately 141,000 Prii last year at around 40,000 metric tons, which also equates to tremendous amounts of CO2.

To help curtail this pollution, waste and expense, Toyota is experimenting with a fuel-efficient diesel-hybrid-solar ship .

We have not been able to acquire data to do a full apples-to-apples comparison along these lines between the Prius and the U.S.-produced Volt, however, which also contains imported components, some being costly, bulky, and required to be shipped in too.

General Motors does have plans for next year to begin domestically producing the Volt's for-now imported battery cells which Volt Line Director Tony Posawatz told us would also result in significant cost reduction.

Gas 2.0