Using the Chevrolet Volt (based on GM's Delta platform shared with the Chevrolet Cruze) as an example, using GM Canada's online build estimator in January 2018, a basic 2018 Chevrolet Volt LT has an MSRP of $40,490 with a cash purchase cost of $28,101. In comparison, a basic 2018 Chevrolet Cruze LS Automatic has an MSRP of $21,953, a difference of $6,148 ($6,947.24 with Ontario HST). Using the most optimistic estimates, the Volt can travel its rated 85 km on its 18.4 kWh lithium-ion battery (65% allowable = 12 kWh usable). That translates to 14.1 kWh/100 km. Using Ontario's off-peak rate of 6.5¢/kWh, a full charge on the battery costs $0.78 (simplified estimate) so the "fuel" cost is $0.92/100 km. In comparison, the Energuide fuel efficiency ratings for the Cruze LS Automatic are 7.9 L/100 km (city) and 5.9 L/100 km (highway), If we optimistically assume 100% city driving and gasoline costs $1.20/litre, the fuel cost for the Cruze is $9.48/100 km. The fuel savings to drive the Volt in 100% electric mode is $8.56/100 km.
Let's pretend that we commute with the Volt 85 km a day (no battery degradation), 5 days a week, 50 weeks/year, and recharge overnight at home. The Volt will then save us $1,819/year. The simple payback on fuel savings is therefore 3.8 years most optimistically, not including the cost of the home charging station. The reduced costs for maintenance should improve the payback somewhat. Driving the Volt 85 km/day and 365 days/year saves $2,656/year and improves the payback to 2.6 years. Obviously, a longer commute with a recharge at work further improves the payback.