On this site we bandy about a lot of numbers, if you are wondering where we get these numbers, you are in the right place.

Greenhouse Gas Emissions (GHG)

Current Diesel Fleet

The base data for these calculations is from OC Transpo’s 2016 stats here.

Total Fuel 42,460,000 l
GHG kg CO2e/l 2.66
Optimistic Well to Wheel Factor 1.1
GHG Emissions 124,238 tonnes
Realistic Well to Wheel Factor 1.46
Emissions 164,898 tonnes

We use a round number of 125,000 tonnes of CO2e per year throughout.  Well to wheel factor takes into account the emissions of fuel production.  The optimistic well to wheel factor assumes diesel from crude oil from Saudi or the North Sea, the realistic number is representative of Canadian sourced diesel, mostly from bitumen.

Future Electric Fleet

Using the same bus kilometers as 2016, we can work out how much electricity will be used by a similar fleet of electric buses.    Note that 1.2 kWh/km efficiency number is pessimistic, CUTRIC uses 1.02 for Canada.  The overhead for charging is added in at 25%, this is also pessimistic and is likely going to be closer to 10%.  We are using 40 g/kWh GHGs, this is the average for Ontario, charging at night would tend to lower this number.

Bus kms 61,772,436 km
Electric Bus efficiency 1.2 kWh/km
Overhead 25%
Fleet power usage 92,658,654 kWh
Ontario Grid CO2 40 g/kWh
Emissions from generation 3706 tonnes
(Diesel emissions avoided) -124,238 tonnes
(Total emissions avoided) -120,532 tonnes

The overall improvement is about 97% reduction in GHGs, we use 95% as a round number.

Operational Cost Savings


We have calculated the cost savings based on 90c per litre of diesel which is optimistic and 10c/kWh which is pessimistic 1-2c is more realistic.

Electricity Price $0.10 /kWh
Fleet power usage 92,658,654 kWh
Electricity Cost $9,265,865
Diesel Price $0.90/l
Total Diesel 42,460,000 l
Diesel Cost $38,214,000
Cost savings $28,948,135

We round the fuel savings to $30,000,000, the actual number could be as much as $45,000,000 if diesel is at $1.10/l and electricity at 2c/kWh.


Maintenance is one area where we do not have data from OC Transpo.  We have drawn a parallel with New York City.  Judah Aber reports that New York Spends $35,000 US on maintaining each bus in their fleet each year.  We make the assumption that OC Transpo spends about $50,000 on each bus each year.  Aber states: “In aggregate, the cost savings has been demonstrated to be as high as 50% per bus. For purposes of this analysis, the Alternative 1 savings for maintenance cost has been set at 40%.

We have adopted the same 40% number, giving a saving of $20,000 per year per bus.

The practical results from King County Metro Battery Electric Bus Demonstration show a 44% reduction in maintenance costs, further supporting 40% as a planning number for OC Transpo.

Overall Operational Savings

We are using a $50,000 per year per bus number for about $50M per year for the fleet, this is supported by fuel savings in excess of $30,000 and maintenance cost savings of about $20,000.  We believe this number to be conservative.

Air Pollution

The annual air pollution created by OC Transpo is as follows:

NOx 1.5 g/km 92,659 kg
PM2.5 0.017 g/km 1,049 kg
PM10 0.178 g/km 11,008 kg

The NOx number comes from the California Air Resource Board (CARB)

The Particulate numbers come from the US EPA

These numbers are optimistic as they are per km measure.  As OC Transpo idles buses extensively, the real numbers are likely much higher.

OC Transpo Bus Efficiency

Total Diesel 42,460,000 l
Passenger km 1,036,600,000 km
l/100 passenger km 4.10

On average, it takes 4.1 l of diesel to move each passenger 100 km. For reference, a Toyota Prius uses 4.5 l of gasoline to drive 100 km.