Plug-in Economics for Prius Prime

According to Toyota, our new 2020 Prius Prime PHEV gets around 4.3L / 100km of city driving. We will use this number since it is not too far off of the combine driving number of 4.4L / 100km. This means at the time of writing this post, the current fuel price at our neighbourhood pump is at $1.15 / L. If you do some fancy math, the Prime will yield us 20.2km per dollar invested at the pump (20.2 km/$).

Ontario Electricity Costs (Fall of 2019)

As depicted by the chart on the right, in Ontario we have three tiers of charging rates. The Prime in the winter can do about 35km with a 9kWh battery. The exact numbers are 40km / 8.8kWh, but this is perfect condition, and we use some battery for heating the vehicle. This will yield us the following:


So by comparing the above numbers, it makes perfect sense to charge the vehicle during Off and Mid Peak hours, and not so much during On-Peak hours. However the On-Peak comparison is so close that if the mileage rating was at 4.5L/100km then it is a wash.

With a bit more fancy math, you can actually calculate how much does gas have to cost per Litre before On-Peak charges make sense. This turns out to be around $1.24/L.

Hopefully you find this information helpful.

Let’s Plug-In

On October 30th, 2019, we purchased a Toyota Prius Prime 2020, choosing the Upgrade trim without the technology package. We traded in our 2012 Toyota Sienna 8 passenger Minivan with approx. 90,000km for $11,000. After all the government incentives, fees, taxes, and dealer’s rebates, we ended up forking out less than $27,000 for the vehicle. The only thing we opted for was the rust protection device.

We now have this plug-in hybrid electrical vehicle (PHEV) for almost a week. The vehicle is very comfortable to drive, and much more refined than my 2013 Subaru Impreza. The Prius comes in three drive modes, Eco, Normal and Power. I find the Eco mode to be too slow and has too much accelerator latency. I prefer the Normal mode. The Power mode can be pretty fun especially when you have a fully charged battery.

There are plenty of YouTube videos and written articles already talking about how the car drives, and I agree with their positive take on the Prius Prime. Therefore, I won’t repeat what has already been said. I will focus on what impact the ownership of a Prius Prime has on our residential electrical consumption.

We have yet to invest in a level 2 charger (240V – 16A) for the house yet, so we are just using our regular 120V plug to charge the 8.8kWh battery for the vehicle. So instead of charging the vehicle in 2 hours with the level 2 charger, we find that it takes around 5 hours to fully charge the vehicle. Toyota’s charging specification is pretty dead on and accurate here.

I raided our utility company’s web site and was able to extract the following graphs. Either click on the image or this link to open the graphs.

The consumption graphs above points to a day with no electrical vehicle as a baseline, followed by three days of charging the Prius Prime in the evenings. It looks like charging the Prius only amounts to an average of 1.5 kWh increase from baseline per hour of charge. The graph shows about four hours of heavy charging follow by a lower power charge during the last hour and a half.

At the current off-peak rate of ~$0.10 per kWh, we are looking at about an increase of less than a $1 per day, and this gives you about a realistic 36km of pure EV mode (all electric) of range per charge. So for a month, $30 will give you around 1,000km of range!

We have driven the car for about 5.5 days, and racked up in excess of 300km. We still have 7/8 of a gas tank left, and the only reason why we used the gas is due to a test drive to the Toronto Premium Outlet mall in Milton. Otherwise our daily usage pattern, which consists of largely local errands, would allow us to just keep on using the battery.

Now the game is up. How long do you have to wait for me to update this blog entry when I fuel up our new Prius Prime for the first time? Watch and see, any wagers?