Using the Chevrolet Bolt (similar to GM's Gamma platform used by the Chevrolet Sonic) as an example, using GM Canada's online build estimator in January 2018, a basic 2018 Chevrolet Bolt EV LT has an MSRP of $44,895 with a cash purchase cost of $32,506. In comparison, a basic 2018 Chevrolet Sonic LT Automatic has an MSRP of $19,903, a difference of $12,603 ($14,241.39 with Ontario HST). Using the most optimistic estimates, the Bolt can travel its rated 383 km on its 60 kWh lithium-ion battery. That translates to 15.7 kWh/100 km. Using Ontario's off-peak rate of 6.5¢/kWh, a full charge on the battery costs $3.90 (simplified estimate) so the "fuel" cost is $1.02/100 km. In comparison, the Energuide fuel efficiency ratings for the Sonic LT Automatic are 9.3 L/100 km (city) and 7.0 L/100 km (highway), If we optimistically assume 100% highway driving and gasoline costs $1.20/litre, the fuel cost for the Sonic is $9.32/100 km. The fuel savings to drive the Bolt in on a long distance commute is $8.30/100 km.
Let's pretend that we commute with the Bolt 300 km a day (no battery degradation), 5 days a week, 50 weeks/year, and recharge overnight at home. The Bolt will then save us $6,223/year. The simple payback on fuel savings is therefore 2.3 years most optimistically, not including the cost of the home charging station. The reduced costs for maintenance should improve the payback somewhat. Driving the Bolt 300 km/day and 365 days/year saves $9,086/year and improves the payback to 1.6 years. As with the Volt, a longer commute with a recharge at work further improves the payback.
If you're commuting in GTA, it is likely that your Sonic will never get highway fuel economy due to gridlock so an electric vehicle will have even better economics.