In a report on a recent Harris Poll, AMN reports that despite relatively impressive sales figures for electric cars, sales have been flat.

The past two years (2013, 2014) each saw sales for this segment exceeding the half-million mark, and 2015 is on track for a repeat, according to a recent Harris Poll. As of the end of July, nearly 290,000 vehicles with a battery generating at least some of their momentum have been sold in the U.S., including nearly 120,000 plug-in models (whether pure electrics or plug-in hybrids).

Yet, while that is indisputably a lot of vehicles, 2015 sales numbers to date still represent the same 3 percent of total U.S. vehicle sales seen in 2012, before some major players joined the charge.

In related news, Audi has announced plans to introduce an all-electric SUV to compete with the Tesla Model X. The Audi e-tron quattro is expected to be released in 2018.

The Harris Poll’s results point to the cost of electric and hybrid vehicles as the main detriment to further growth. Internal combustion engines are expected to continue to be the primary mode of power generation for at least several more decades.