Prius shopping round 2 - the heat is ON!

January 19, 2018 10:07 AM

So, subsequent to my previous question, I ended up leasing a 2015 Prius, and so far it's been great. The lease is almost up, and I'm thinking of buying the car, but have a question.

The only real downside to having a Prius in Toronto is that I have to use the heat a fair bit in the winter. I keep the heat on 18 degrees with a low fan setting most of the time, but it still gets a lot of use, and this puts a strain on my fuel efficiency. I usually get about 5L/100km when it's above freezing, but in the last month it's been closer to 7L because of the frigid temperatures we've had.

My question -- are newer Prius models any better in terms of heat affecting fuel efficiency? My current model has pretty low mileage so it might be a good deal to buy it but if a newer one gets more per litre, I might consider getting a new lease.

posted by greatgefilte to Travel & Transportation (5 answers total)

Well 100,000km at frigid temps the difference is 2000L of gas. (Assuming half the year you dont need the heat, thats ballpark 8-10 years of use?) Even at crazy high BC gas prices of $1.40/litre, thats about $2800 extra in fuel savings if the new Priuses have totally solved the problem (no idea if they have). All other things aside, is the cost of a new lease going to be more or less than the potential fuel savings?
posted by cgg at 10:45 AM on January 19, 2018

Best answer: Any hybrid will consume significantly more gas when heat is turned on, because the heat isn't all waste heat from the engine anymore - the engine can be running just for heat! This is also true, to a lesser extent, for cars equipped with an auto stop system. Plus driveline losses are higher in all cars, due to the lower temperature and extended warm-up time of lubricants, etc. Any car gets poor gas mileage at low temperatures, it's just more apparent (and larger as a fraction of total energy consumed) on a hybrid.

The Prius Prime (Plug-In) has a heatpump so it might be a bit better in mild-moderate cold as it will allow the car to generate some of its heat off the battery, keeping the engine off longer and wasting less gas running the engine just for heat. It's similar in efficiency in gas mode to the standard Prius, so even if you never charge it it should get similar gas mileage in general.

All that said, I'd never even consider replacing it! You'll never make back the transaction costs and additional depreciation from starting again with a new car, and that 2015 Prius will continue to be reliable for many years in the future.
posted by doomsey at 11:25 AM on January 19, 2018

(my Volt runs the gas engine to supplement heat whenever it's under 15F / -10C, no matter what. I know why it's doing that, and it actually makes sense from a cost perspective, but it's literally getting 20MPG indicated in that use case! So frustrating.)
posted by doomsey at 11:30 AM on January 19, 2018

Best answer: Have you experimented with different fan settings? I’m wondering if a high fan speed would let you get up to temp faster, enabling you to turn off the heat sooner and use less energy overall.
posted by actionstations at 11:44 AM on January 19, 2018 [1 favorite]

Response by poster: Will try the different fan settings to see if it helps! Either way, I think I'll be keeping this Prius until I live somewhere with plug-in capability.
posted by greatgefilte at 8:55 PM on January 19, 2018