Four years after buying more than 170 hybrid buses, each costing more than regular diesel buses, OC Transpo could be forced to turn all of them into strictly diesel buses.

David Jeanes, president of Transport Action Canada, says the hybrid buses are inefficient. (CBC)

"There is no doubt that they have been underperforming. We thought we'd get a lot more fuel efficiency out of these hybrid propulsion systems than we have gotten. And at this point they're running out of warranty and we know the component maintenance parts are really high cost," said Coun. Diane Deans, chair of the transit commission.

Each hybrid bus costs anywhere from $100,000 to $150,000 more than regular diesel buses. The city made the investment because it hoped to save on fuel costs.

Instead, the city spent $1 million more on diesel fuel than it expected to last year, Deans said. It also cost more than $7 million to replace the batteries on some hybrid buses last year.

In light of the underperformance, the city's draft budget for 2013 includes $550,000 for a pilot project to rip out the hybrid electric/diesel engines and replace them with regular diesel engines.

If successful, pilot project could be expanded

If that project is successful, Deans said all 177 hybrid buses will eventually be retrofitted. Deans said it's expected to cost about $75,000 per bus, or more than $13 million.

Craig Watson, president of the Amalgamated Transit Union Local 279, says the city spent a lot on an unproven technology. (CBC)

"We paid a good deal more than for regular buses in the first place, we already paid once because we got the wrong type of batteries … now we're going to have to pay again, and when we're done, we're essentially going to have just diesel buses, which we could have bought more cheaply in the first place," said David Jeanes, president of Transport Action Canada, a group that advocates for better public transit.

"I think the former management team at OC Transpo really didn't do the research," said Craig Watson, president of the local transit union. "They didn't follow up on what was happening in other properties such as Toronto. The hybrid bus has not been successful anywhere; it's particularly ineffective in Ottawa due to our route structure."

Watson said that before the hybrid buses arrived in 2008, battery problems and other issues were being reported in Toronto.

He said the hybrid buses perform best while making frequent stops and starts in downtown areas. During longer hauls on the Transitway, for example, the diesel engine kicks in.

"It's a lot of buses to go into a technology that isn't proven yet," Watson said.

City council is expected to vote on the draft budget in November.