Clean Energy Fuels isn't the only company struggling from the slow adoption of natural-gas technology. Westport Innovations also saw its growth decelerate abruptly. At issue is the rise in natural gas prices during the winter, which exposed the downside of committing to expensive nat-gas conversions. If prices keep climbing, then it'll take longer for conversions to pay off from a fuel-cost savings standpoint, and that could deter many users from getting those modifications made, hurting both Westport and Clean Energy. Still, Clean Energy Fuels is working hard to strengthen its position, opening two new LNG stations about a month ago, and announcing a broader partnership with delivery giant UPS to use the new stations as part of its growing network.