It took more than 11 years, but U.S. sales of hybrid-electric vehicles have topped 2 million units, according to Ward's data.

Hybrid deliveries fell 3,217 units short of the milestone last month, but using May’s modest daily sales rate of 696 as a basis for June, the gap already has been bridged, Ward’s calculates.

The selling rate though May was 1,006.

The Honda Insight, which made its debut in 1999, was the first hybrid to go on sale in the U.S. But the Toyota Prius – which launched in June 2000 – popularized the technology, accounting for more than half of the market’s total hybrid sales.

Through May, the Prius, now in its third generation, had notched 1.018 million deliveries, according to Ward’s. Insight sales stood at 65,566.

Hybrid sales growth has been painstaking, though the market has seen spikes when fuel prices surged. Industry watchers have cited cost as a reason for the low take-rate. A new hybrid easily can top $30,000.

However, cross/utility vehicles are similarly priced and they tallied 2 million cumulative sales in 2001, just seven years after their U.S. market debut. The segment now regularly racks up annual delivery totals of 2 million units.

Hybrid sales eclipsed 1 million in 2008. Thanks to an explosion of nameplates and the continuing popularity of the Prius, the segment took less than three years to accumulate its second million.

Following the Prius, the No.2 all-time best-selling hybrid in the U.S., is the Honda Civic Hybrid. On sale since 2003, the car has recorded 192,801 deliveries.

The third, fourth and fifth spots all are held by Toyota. The Camry Hybrid, which debuted in 2006, is No.3 with 174,571 sales, followed by the Highlander Hybrid CUV with 112,106. It bowed in 2005.

Toyota’s Lexus RX hybrid CUV, which launched in 2005, ranks fifth with 108,022 deliveries. Close behind is Ford’s Escape Hybrid, with 107,122 sold since its introduction in 2004.

Despite national average gas prices that have been hovering near $4 per gallon this year, hybrids remain a blip on buyers’ radar. They accounted for only 2.3% of the light-vehicle market through May, which marked the segment’s poorest monthly performance in 15 months, according to Ward’s.

In comparison, 20.8% of North American-made ’10 vehicles, the most recent data available, were equipped with V-8 engines.

– with John Sousanis

cschweinsberg@wardsauto.com