The Economics of Hybrid Buses

The City of Toronto’s Executive Committee agenda for October X contains a report on the City’s Green Fleet Plan for various agencies.  By far the biggest of these is the TTC, and in an accompanying report, we learn just what the economics of the hybrid bus fleet are.

On page 15, the TTC presents a chart showing the fuel efficiency of its fleets, and it is worth noting that fuel consumption per vehicle km is rising at the same time as the average capacity of the vehicles is falling.  This is partly due to the additional systems, notably air conditioning, that are present on newer vehicles.

Of the total fleet, just over a quarter (450 out of 1653) are hybrids, and these consume about 10 percent less fuel than their pure-diesel cousins (based on experience to date).  This implies that the increased fuel consumption on the diesel fleet is even higher, proportionately, than the consolidated figures imply because of the offsetting benefit of the hybrids.

In the longer term, the relative fuel savings of hybrids may rise as they operate on routes with dense, stop-start traffic where the benefit of electric propulsion and battery energy storage will shine.  Nonetheless, there will be a considerable net cost of owning hybrid buses relative to diesels over their lifespan.

The TTC expects to spend $110-million on diesel fuel in 2009.  This includes a saving of $3.6-million for the existing hybrid fleet, and that saving will rise to somewhere around $6-million annually by the time that the fleet is about 50% hybrid (854 out of 1864) in 2011.  That’s a per vehicle saving of  about $7,000 per year.  We do not know yet what savings, if any, on maintenance will accrue to the hybrid fleet.

The capital cost premium for a hybrid bus is about $200,000, and the hybrid saving is only about 3.5% per year on this additional investment.  In time, if the capital cost premium comes down, the cost of fuel goes up, or the average percentage saving across the fleet rises, the numbers will converge and the rate of return will improve.

Meanwhile, it’s a shame we don’t have comparative figures for the cost of trolleybus infrastructure for our major routes.  Two decades ago, the TTC sacrificed its trolleybus system on the twin altars of environmental responsibility and natural gas buses.

Postscript:  The supposed economic advantage of natural gas as a fuel was almost entirely due to the fact that it was not taxed.  A large chunk of the TTC’s annual fuel bill is in tax paid to the Province of Ontario.  Without this tax, the economics of buses in general would be rather different.  Oddly, because the dollar saving from reduced fuel consumption would actually be lower without the tax, the economics of hybrid buses would look even worse if this tax were rescinded.