How this calculator works
A plug-in hybrid has a battery that can be charged from the mains and an engine for longer trips. Its economy depends on how often the trip fits inside the electric range: a 20 km commute in a car with 50 km of range is all electric, while a 200 km trip is mostly petrol. The calculator charges each trip to the battery up to the range and uses petrol for the remainder, so the split changes with the trip length rather than being a fixed percentage. Electricity is priced per kilowatt-hour and petrol per litre, and the two are added to give a monthly cost. The comparison car uses petrol throughout at its own litres per 100 km. Emissions combine the electricity at the Canadian average of 0.12 kg CO2e per kWh with petrol at 2.31 kg per litre; the provincial grid mix can move the electricity part from near zero in Quebec and British Columbia to over 0.5 in Alberta.
Formula
electric distance per trip = the smaller of trip distance and electric range. electric km = trips x electric distance per trip. total km = trips x trip distance. petrol km = total - electric. electricity (kWh) = electric km / 100 x kWh per 100 km. petrol (L) = petrol km / 100 x litres per 100 km. cost = electricity x price + petrol x price. emissions = electricity x 0.12 + petrol x 2.31.
Worked example
Forty round trips of 40 km a month with a 50 km electric range: all 1,600 km are electric, because every 40 km trip fits. Electricity is 1,600 / 100 x 18 = 288 kWh, costing $34.56 at $0.12 per kWh, with no petrol. A regular car at 8 L/100 km uses 128 L, costing $204.80, so the monthly saving is $170.24 and the annual saving is $2,042.88. Emissions are 288 x 0.12 = 34.6 kg CO2e a month.
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Frequently asked questions
Why does the trip length matter so much?
The battery covers a fixed number of kilometres, so short trips use it fully and long trips use only the first part. A 100 km trip in a car with 50 km of range is half electric, no matter how efficient the engine is. Frequent charging between short trips is what makes a plug-in hybrid work.
Is a plug-in hybrid better than a full electric car?
For a driver whose trips fit the electric range and who can charge at home, a full electric car has lower emissions and running costs because it carries no engine. A plug-in hybrid suits people who regularly make long trips and cannot rely on charging, at the cost of carrying two drivetrains.
Does the calculator include charging losses?
No. Charging from the wall takes more electricity than the battery stores, typically 10 to 15 percent more. Add that to the consumption figure, or enter a higher kWh per 100 km, to account for it.
What if I never plug it in?
Then it runs mostly on petrol and carries the weight of an unused battery, so its economy is worse than a conventional car of the same size. The savings in this calculator assume the battery is charged before each trip.