Prius v (lowercase v for the Prius v wagon), EV Mode, ECO Mode and cold operation

EV mode is designed to function once the engine is warmed up, primarily to reduce engine emissions. Toyota does not allow much discharge of the battery in order to make it last over 100,000 miles, maybe 200,000. As a result, Prius hybrids usually can't go more than a mile or two on EV under any circumstance. The battery is primarily a short term energy storage device so energy regenerated going down hill or when braking is available for uphill and accelerating. There are "hypermiling" techniques to maximize mpg (maybe 37% improvement), but that technique is more about varying speeds widely, coasting, drafting semi-trucks like you were a NASCAR driver, maximum air pressure, no extra weight, etc etc. Keep your speed down and use ECO mode is good advice. Otherwise consider a full electric car like a Tesla.

How to Hypermile (with Pictures) - wikiHow

 

First, there is no correct way to use EV mode, only what's most efficient for a certain condition. Second, by forcing EV mode or trying to stay in EV mode, you are doing the opposite of what you want and increasing your fuel usage. Follow below for efficient driving tips:

 

There's a variety of uses for it. I use it to coast down a hill. Don't need the engine running for that. I also use it to repark the car when someone is in my spot after I get home. Unfortunately, you can't do that when the engine is cold. It's also nice to use it to get in and out a parking lot. There's a lot of waiting at a parking lot where running the engine isn't necessarily most efficient.

 

I think the EV mode button is a "bell and whistle" rather than a really useful function, eg the ability to manually control electric only. The Prius models through 2009 did not have it although people figured out how to hack one in. The reality is I can keep it in EV mode for parking lots by taking it easy and watching the indicator. Conversely, even if you have it in EV mode, it will jump out quickly when more power is needed. The battery is there to provide extra power for the relatively underpowered engine when needed and to allow the constant stop start of the gas engine and still have immediate power when the gas engine is off.

The auto EV mode will do more than you think when it's essential. I once ran out of gas in my 08 Prius doing 60 mph on the freeway. The battery kept me going at speed for at least three miles to a gas station. Once I had gas and the engine started, the HV battery was almost fully discharged. Engine only power was extremely weak, barely able to get on the road again and I probably took a few months off the HV battery. I have never experienced such low engine power before or since because the HV battery is always available to add extra power to the engine when needed.

 

Probably not. As discussed, the engine will turn on if temperature is too low. There's no hazard with low temperatures besides using more fuel when it's cold.

In contrast, the hazard usually discussed is if temperature is too high. On hot days, it is recommended to use AC to cool the cabin which cools the battery instead of sweating without AC. You might use more fuel but you'll prolong battery life.

 

congrats and welcome! is it spring up there already?

 

Don't forget that if cabin heating is called for, Prius will burn fuel.
If not, it will shut down the engine much sooner after starting to drive.

You can install and use electric engine block heater / cabin heater to preheat the car and save fuel.

 

A block heater is strictly a comfort measure, it won't save any money. In fact it will cost more to use than to not use. But we're talking about pennies either way.

 

I agree that it is pennies that we are talking about.
Whether it costs more or not depends on the price of gas and electricity.

VTT (Technical Research Centre of Finland) conducted a study a couple years back.
Incidentally one of the vehicles in the study was Prius+ (European name for Prius v).

The conclusion was that it does save some fuel while the main benefit is reduced emissions (mainly unburned hydrocarbons, carbon monoxide and nitrous oxides). All in all they recommend engine preheating.

Fuel consumption was measured using NEDC cycle (20 minutes of driving including both city and highway driving).
In -7 C (about 19 F) the combined fuel consumption was 8.10 l/100 km (29.0 MPG US) without preheating and 7.71 l/100 km (30.5 MPG US) after two hours of preheating with 300 W EBH.
Energy-wise preheating consumed 0.6 kWh electricity and saved 0.44 kWh worth of fuel.

The report can be found in here http://www.motiva.fi/liikenne/henkiloautoilu/taloudellinen_ajotapa/moottorin_esilammitys/tutkittua_tietoa_esilammityksesta.

Unfortunately I couldn't find English translation.

 

The North American block heater is 400w, not 300w. My personal experience suggests it does help for about 2 min. You can also let the car sit and idle for that same 2 min and get about the same heating benefit. The question will be which uses more energy. There's credible evidence right here in numerous threads that the 2 min idle might save gas, or at least not cost any.
I think the block heater is a good option for personal comfort if a warm-up idle isn't for you.