How do you know how much electrical charge is left in the Prius Prime PHEV?

Press the button on the right side of the steering wheel to change the menus on the MID to the "Settings" menu. Press "Enter" ( )





Press to scroll through the Settings menu until you reach "Meter Customise" . Press . Scroll up/down until you see "HV System Indicator". Press then scroll to "EV Drive Monitor". Press . Select EV Energy.


Keep pressing "Back" until you exit the Settings menu. You should see the EV Distance change to a % based SOC readout (see below) on the Hybrid System Indicator screen.

 

Np. You can use @schja01 's method to have both the EV Distance Remaining and the SOC% displayed at the same time if you wish to build some sort of correlation. Not sure if it works. I have the Upgrade w/ Technology Package so I use the HUD to display the Distance Remaining. I find it fairly accurate after you've driven about 5-10km. It's not accurate at the start of the day because it's only based on the last drive so if it was warm the day before and it got cold today, your EV range will be wildly optimistic until it figures out you're using the heater and the battery is cold etc then it'll adjust. E.g. if it says 60km in the morning after a full charge, I'm usually getting 52-55km depending on traffic. It's least accurate during transition months like Spring and Autumn since changing or fluctuating temperatures can play havoc on range, especially a range this short).

Your 40km range will change depending on your driving habits, outside temperature, tyre type (all-seasons, winter), climate control setting (temperature setting, heater use, cooling use), road surface (snow covered, standing water or bare dry roads) etc.

I've ranged from 25km to 63km between the seasons. It's ok to use fuel in the winter since you'll probably not use any fuel in the summer (unless you have a long commute) and so it's good to "purge" the tank once a year imo. (And the owner's manual recommends adding at least 20 litres of fuel in total every 12 consecutive months).

Or something that's easier to compare (using the Eco Diary page). In the summer, I'm at 9.1-10.5kW/h100km. In the winter with rain or snow, I'm closer to 15-18kWh/100km. Once it rains, your consumption goes up due to water on the road (Extra drag) and then factor in the colder temperatures and usage goes up.

 

Well the number given is meant to average over the entire year which if you think about it, is pretty close given my usage case (unless you live in the Prairies with extreme cold or in Atlantic Canada with heavy dumps of wet snow, both will significantly reduce range and in the case of the Prairies, you'd be running the engine for heat below -10°C).

63km was my record. I typically get 50-55km in the summer. Also, 25km was my worst ever.

2020 Prius Prime and Extreme Cold... | PriusChat
(I had 5km range left so I estimated 25km). AM temp was -7°C and PM temp was -3°C.

The 40km is based on 15.8kWh/100km energy consumption so if you're beating that, you'll get more than 40km.

Note that as winter approaches, pre-heating the cabin becomes important - it allows you to pre-heat the cabin using wall power (mostly... minor details if you want me to explain) so when you drive off, your climate control only needs to maintain the cabin rather than heat it from a cold start (which draws a lot of power). In addition, it helps keep the battery warm (again for more range). At 5-10°C, you'll probably see a 2-3% SOC hit starting with a cold cabin and battery. I assume more if it's at or below 0°C.

Here's a link to estimated electrical consumption of various electrical items on the Prius

Estimated EV penalties for various heating cooling and lights | PriusChat

(mid beams... he means parking lights. and normal being low beams)

 

Page 223/224 of the owner's manual. The Eco Diary is the easiest to find the kWh/100km readout. Unfortunately, there's no "trip" readout like there is for L/100km. You only get instant (which is useless since the scale tops out at 10kWh/100km and you're usually above it) and the Eco Diary which is a daily and monthly average. I use the daily one since that's the closest I can find for short term readouts.

Drive Monitor 2 that @Salamander_King suggests is for long term (as long as you did not reset the "odometer" fuel consumption average via the TRIP button or accidentally press "Update" on the 7" MFD on the Consumption Screen page.)