Quick report: San Mateo, CA to Furnace Creek (Death Valley), 1060 mi round trip in Taycan Turbo

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efficiency compares between the two powertrains

Here are some data about the differences in range (not efficiency, but related).
Source: The base Porsche Taycan's EPA range numbers are super-easy to beat

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how the efficiency compares between the two powertrains

They are not far apart.
Here is a link to a detailed sheet on the models.
the Turbo MPGe (EPA) is 73 while the Turbo S is 70 MPGe

But EPA numbers are quite a bit different than AMCI and WLTP ranges. Here are some other data. Though not efficiency, it is related: