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 factor^{Footnote 12} ) × (engine displacement in litres^{Footnote 13} )

= (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)^{Footnote 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 vehicles^{Footnote 15}
= 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 vehicles^{Footnote 16}
= 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 ^{Footnote 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?

The following table provides data for three types of engines based on number of cylinders for idling time to a maximum of 10 minutes per day. The calculation method for each table value is the same as that for question 1.

Idle Time	Fuel Use (litres per year)			CO 2 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 ^{Footnote 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 ^{Footnote 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