Arriving at Calculations

1. How does NRCan arrive at the fuel, CO₂ and dollar amounts quoted in the messages for three minutes of idling?

Per Vehicle Calculation:

Idle time per day = 3 min per day = 0.050 hours per day

Idle fuel flow (L/hr) = (idle fuel flow factor12 ) × (engine displacement in litres13 )
	= (0.6 litres/hr per litre of engine displacement) × (3 litres) = 1.8 litres per hour
Idle fuel use (L/year) = (idle fuel flow) × (idle time per day) × (days in year)
	= 1.8 L/hr × 0.050 hr/day × 365 days/year = 32.85 litres per year
Idle CO2 emissions (kg/year) = (idle fuel use) × (CO2 emission factor)14
	= 32.85 L/yr) × 2.3 kg/L = 75.56 kg per year
Idle fuel cost ($/year) = (idle fuel use) × (cost of fuel)
	= 32.85 L/yr × $1 per litre (assumed) = $32.85 per year
Canada-Wide Savings – Per Year based on the year 2007:
Fuel savings (litres/year) = (fuel use per vehicle) × (number of vehicles)
	= 32.85 L/year × 19,198,960 vehicles15 = 630,685,836 L/year = 630 million litres per year
CO2 savings (tonnes) = (CO2 emissions per vehicle) × (number of vehicles)
	= 75.56 kg/year × 19,198,960 vehicles16 = 1,450,577,423 kg/year = 1,450,577 tonnes/year = 1.4 million tonnes per year
Cost savings ($/year) = (fuel cost per vehicle) × (number of vehicles)
	= $ 32.85 × 19,198,960 vehicles 17 = $ 630,685,836 per year = $ 630 million per year
Number of vehicles off road = (fuel savings) ÷ (annual fuel use per vehicle)
	= 630,685,836 l/year ÷ 1,950 L/year = 323,429 vehicles = 320,000 vehicles

Canada-Wide Savings - Per Day:

The following values were calculated using the Canada-wide savings per year and dividing by 365 days:

• Daily fuel savings: 1.7 million litres per day
• Daily CO₂ savings: 3,974 tonnes per day
• Daily cost savings: $1.7 million per day

2. My vehicle's engine size and idle times are different than the examples in question 1. Can you tell me what my fuel use and CO₂ emissions are per year?

Idle Time	Fuel Use (litres per year)			CO2 Emissions (kg per year)
(minutes per day)	1 litre Engine	3 litre Engine	5 litre Engine	1 litre Engine	3 litre Engine	5 litre Engine
1	4	11	18	9	25	41
2	7	22	37	16	51	85
3	11	33	55	25	76	126
4	15	44	73	34	101	168
5	18	55	91	41	126	209
6	22	66	110	51	152	253
7	26	77	128	60	177	294
8	29	88	146	67	202	336
9	33	99	164	76	228	377
10	37	110	183	85	253	421

3. How can a vehicle produce about three times its own weight in CO₂ each year?

Ratio = (annual fuel use per vehicle × CO2 emission factor) ÷ (average vehicle weight)
	= (1,950 L × 2.3 kg CO2/l) ÷ 1,450 kg = 4,485 kg ÷ 1,450 kg = 3.093 = 3 times its own weight

4. How does idling for just 10 minutes use over 1 cup of fuel for a vehicle with a 3 litre engine and over 2 cups of fuel for a vehicle with a 5 litre engine?

Idle time = 10 minutes = 0.166 hours

For a 3 litre engine:

Fuel use = (idle time) × (idle fuel flow factor 18) × (engine displacement)
	= (0.166 hr) × (0.6 L/hr per litre of engine displacement) × (3.0 litres) = (0.166 hr) × (1.8 L/hour) = 300 ml = 300 ml ÷ 236 ml per cup = 1.3 cups

For a 5 litre engine

Fuel use = (idle time) × (idle fuel flow factor 19) × (engine displacement)
	= (0.166 hr) × (0.6 L/hr per litre of engine displacement) × (5.0 litres) = (0.166 hr) × (3.0 L/hour) = 500 ml = 500 ml ÷ 236 ml per cup = 2.1 cups

Note: 1 cup = 8 fluid ounces = 236 millilitres

12 Review of the Incidence, Energy Use and Costs of Passenger Vehicle Idling; Gordon W. Taylor, P.Eng. Prepared for the Office of Energy Efficiency, Natural Resources Canada, 2003
13 In 2005 the average engine displacement for light-duty vehicles was 3.0 litres
14 Actual value: 2.289 kg CO₂/L – National Inventory Report 1990-2006, Table A12-7, April 2008
15 For the year 2007 from Statistics Canada
http://www40.statcan.ca/l01/cst01/trade14a.htm
16 Ibid.
17 Ibid.
18 Review of the Incidence, Energy Use and Costs of Passenger Vehicle Idling; Gordon W. Taylor, P.Eng. Prepared for the Office of Energy Efficiency, Natural Resources Canada, 2003
19 Ibid.