fuel economy vs climate control vs fogged windows

It's a bigger car. The EPA specs has the gen5 at 7 more cubic feet of cabin air heat, plus more cold surfaces to heat up. Then the larger windows mean more heat loss.

Perhaps those window films for keeping heat out will help keep heat in.

 

Larger, heavier, and larger engine car. Larger car meaning larger surface area, mass to heat up. Larger displacement engine burns more fuel and has to move a larger mass. Your pretty much trying to compare apples to oranges. The Prius C had a much smaller traction pack.
You can try to preheat the car while it's plugged-in to off-set some of this, but the engine will kick ON below a certain temperature anyways. As far as defogging the cabin, you can stop breathing or turn AC on, set cabin air to recirculate, and set your cabin temperature. The AC system will dehumidify your cabin to prevent fogging. If it's external fogging, you can only crank up the heat on your window defogger and use your wiper blades.

 

It makes you wonder why they have the "OFF" button, right? LOL. Perhaps it helps with cycling the system on and off manually, lol.

I don't have a PHEV, but I've noticed that on my '26 HEV. Push the OFF button, and sometimes goes immediately into EV mode.

Remember, the previous poster is from Cali.

Snow on boots doesn't help with the fogging.

However 9 l/100km comes out to 26 mpg (us). That really sucks.

I'm also blaming the fuel winter mix. I don't have snows though, yet, lol.

I was bitching about a 53mpg tank that included a 150 mile trip south (300 miles total) from Albany, NY on Christmas Day. Is Toronto that much colder than Albany? Other tanks locally are 55 or so, as I recall.

I also have the hvac system (only) set to "E" as well (have to read the manual to see what that really means, lol) and temp at 70.

Does the PHEV come into play? You're not driving it on battery are you?

It probably runs the engine at times just to heat up the cabin.

My TDI (diesel) Beetle was similar. It took a long time to warm up. People put cardboard on the grille, but I understand our cars have automatic louvers.

On full tank refills, locally driven, I've gotten (actual):
12/11 54.5
12/18 54.6
12/24 56.8
12/29 52.8

 

it is surprising

 

@winnertakesteve : do you have it on Auto? I just have the fan on low and temp at 70f.
edit: I also read the manual on eco mode/heating-seems to control engine speed? Hard to tell from manual for both.

 

Another possible factor is the hybrid vs. PHEV battery differences. The Prius c had the battery in the cabin like Toyota's other hybrids. That and its small size lets it warm up quickly, and it doesn't take much to keep it at the preferred temperature for efficient operation. The gen5 PHV moved the battery to outside the cabin space. It doesn't get the benefit of cabin heating helping with warming up its much larger mass.

 

i know the heat pump is supposed to be efficient, but could it be part of the issue?

 

That's what the PHEV uses for cabin heat?

 

yes down to a certain temp. in ev, the engine will come on to assist or takeover? i'm not sure how they combine. in hv the same process would start immediately, i would think.

their first plug in had no heat pump. so if you wanted heat, you would have to run the engine.

 

Heat pump?

 

Primes have heat pumps.

 

As a factor in poor mpg in cool weather?

 

Recirculate is a good idea if the cabin is already dry and you just want it warmer.

If you're trying to get rid of moisture (fog on the windows) then fresh air is the better choice.

A few grams of snow falling off your boots can have a big impact on the cabin humidity... the more you can kick off during entry, the less your car needs to then melt, evaporate, and eventually eject overboard.

You may be bumping up against the limits of scale. Once the trip is short enough, a smaller car with a smaller engine will always outperform a larger one when it comes to warmup, both in terms of cabin comforts and fuel economy.

 

It is also used in cooling the battery. One would think the battery isn't getting too hot in these conditions.

Using the heat pump will lower EV efficiency, but it shouldn't have an impact when the engine is running. Though the engine coming on for heat could mean it is running in a less efficient mode to generate more heat. If humidity is heavy it will run more to dry air, though that is true of cars with just A/C too.

Check the tire pressure, that can drop a lot in the cold.

How long is the engine on for these trips? It can warm up quick for emissions, but that isn't when it is fully warmed up. It takes time for the oil to reach optimum temp in those conditions. It is cold enough that the engine can lose heat when trying to heat the cabin right away. If you are using EV mode during these trips, the engine may never reach its temperature for best efficiency. Have you tried the trip completely in HV mode?

As for the fogging windshield, you try setting the HVAC controls manually to blow on the windshield. Unlike pushing the defroster button, that can keep the engine off. It won't work as well with high moister, so you might need to turn in one before fogging happens.

 

Have you set vent mode to heat/defog? Besides directing more* air to the windshield, it may surreptitiously activate the AC, at a lower than usual level. That's the case with my third gen, even though the AC button is not lit, Scangauge indicated AC WATTS as a value other than zero, say 50~100.

* I bemoan the demise of a regular vent mode that directs 100% air to windshield, as opposed to 50/50 windshield/footwells. Cars used to have that. Yeah (at least on our gen 3) there's a "front defog" button, but that seems an extreme, short-term state, wouldn't want that constantly.

 

Good points, low tire air pressures - just not low enough to set-off the TPMS. OP may also want to check the battery heater trip points and if that option is toggled ON while plugged-in. I know on the gen4, the option to cool the pack before charging was toggled OFF as factory default, so a look at those options may be warranted to get it to run more efficiently. I know that Canadian electricity prices are much cheaper than the gasoline alternative.

Good Luck.....

 

And this is a Prime/PHV where hitting the front defog button will turn on the engine.