They're a maximum 85% efficiency, with a range of 40-60%, and then you're supplying electricity to a 90% efficiency electric motor. So, overall, you have 90% of 85% of 50% of the generated electricity going into moving your car, so at best around 38.5%.

In contrast, an electric car uses electricity to charge a 99% efficient battery, and discharge to the 90% engine. So, 89% efficiency - much, much better.