Is the electricity really cheaper?

Thanks! I've been reading threads looking for that. Figured SOMEONE is OCD enough to have made that graph already . IF I were paying for electricity (~$0.165/kWh, but I have a solar array that is generating more than we use. The credit expires 1 year after it is earned) the break even cost for gas would be $2.20. Hasn't been that low in many a year, I think 2003. It is currently $2.47 here.

But now I have a different question. How does the EV charge mode work to recharge the traction battery? If I'm cruising a couple hundred miles at 65 MPH, the ICE will be running quite a lot. How much extra gas would I use if I put it in charge mode so I have EV capacity for the surface streets when I get off the interstate? Is it worth doing or should I just run HV home and charge in the morning when the sun (hopefully) comes up?

 

That's been asked before. See those threads.
Charging Mode Efficiency | PriusChat
Cost to charge battery in "Charge Mode" | PriusChat
My first real test of Charge Mode efficiency | PriusChat

My take is that it never pays to use charge mode if saving money or increasing efficiency is the goal.

 

Thanks Salamander

 

Not OCD, I just noticed that this question was getting asked twice a day for a while,
I still think @Danny should make something like my chart a sticky

Ah well

 

Sadly, the gas price has been cheaper than the EV break even point for the last 8 months around my home.

 

Interesting difference between the "Charging Mode Efficiency" and "My First Real Test" threads. The first says to only use Charge Mode on relatively steep inclines, the second says not to use it on steep inclines. My trip to MA next Tuesday includes several steep hills, including a couple where you can gain 15 MPH from 65 MPH with your foot off the accelerator. Charge mode on the up hills or not charge mode? Even if I don't use Charge mode, I should be able to EV all of the non interstate sections round trip. Too bad there isn't an 'instant read' MPG on the ICE like I had in my Gen IIs. It would be easy to tell what the MPG hit is when going into Charge mode on one of those uphills.

Salamander - gasoline is cheap where you live? Or are your electric rates really high?

I agree! Even though I've not driven anything but a Prius (other than a couple of rentals) since Sept 2004, there is a lot to learn with the Prime and knowing if I am saving money/gas/just the environment is important to me and I would guess a lot of other new owners.

 

Read on your manual p200 to use split screen on the main display. You can at least see the visual graph of instant read MPG.

Both, relatively speaking. Our electric rate is ~20c/kwh and gas price has been hovering around $2.30 last 6 month. I also use store fuel credit to lower already cheap gas. My last fill up was $1.79/gal.

 

Thanks, again. I see that is says the current MPG is shown when in HV mode, don't know if it will also do that in Charge mode. But I'll find out.

Clearly your gas is too cheap I'm sure all the people buying trucks and SUVs instead of cars aren't complaining though.

 

Interesting question. I have never used CHARGE mode on my PRIME, let alone the split screen to display current MPG on the display. I am also curious what it will show on EV mode running on 100% electric. Easy to test. I think I will check on my way home today.

 

Instant mpg bar graph works on the Charge Mode. If you switch to EV mode, the bar changes to miles/kwh.

Posted via the PriusChat mobile app.

 

Even if the electricity isn't cheaper, I feel like the improvement in throttle response is justification enough.

 

Well, it's not a chart, but here is how one can compare the cost per mile of gasoline vs electric operation:



The above calculation assumes "all things being equal" -- i.e., your route, traffic, head- and tail-wind, number of traffic light stops, etc. are the same.

Now, the laws of physics are such that charging the traction battery by running in "charge mode" cannot be as efficient because of all the various losses (engine friction, electrical resistance, etc.) than just running in HV mode. The exceptions might be when descending a hill where some some of the conversion of potential energy to kinetic energy would otherwise be lost to braking -- or when using the ICE at highway speed where the additional load of charging might be negligible as a specific engine RPM. (I'll leave it to some pedantic mechanical engineer to calculate this exact point where the ICE is at maximum efficiency.)

If someone would like to create a graph like this, I am sure many Prius Prime suffering from OCD would be appreciative:



However, this kind of graph will not take into account the "all things being equal" variables noted above. These will remain unique to each driver's situation.

As I noted in an earlier post, where I live the electric rate is 20.9-cents per kWh. The cost of regular gasoline is about $2.80 per gallon. Given how I drive and my usual routes, the cost per mile is about the same either way.

That being said, I still enjoy the "feel" of EV driving and, as a bonus, I believe that I am making a small but positive contribution to air quality in my metro area.

 

If you want to know what charge mode does it's probably best to test it on the flat first.
From what I've seen charge mode generally gives the pack about 1 mile EV range for every
mile driven in charge mode.
And mpg is plus or minus 45mpg while in charge mode, depending on speed temp etc.
Charge mode will also only charge to 80% of what the EV range guessameter shows for a fully charged battery.
Charge mode also charges the battery faster than the battery will charge using the plug, but will only charge to 80% of full charge.

I don't use charge mode often, but I'm sure there are a couple of downsides concerning battery temp if using too many full charge in charge mode, full EV discharge cycles consecutively.

 

This suggests that regen braking will charge the traction pack when in Charge mode. I had thought that it charged only from the ICE. If the former is true then going into Charge mode on steep downhills at speed would be 'free' electricity especially if the regular pack was already at or near fully charged (all green in my Gen IIs). If that is not the case, it seems like it would be expensive electricity because the ICE would be working when it would otherwise not be running.

 

It's just a software change, like going from ECO mode to POWER mode. It's annoying when you're trying to hypermile and switching between HV and EV changes throttle sensitivity. The PiP didn't do that.

It can help if your utility has time of use plans. I can charge overnight for $0.13/kWh. Gas is $3.30, so the electricity works out to be half the price of gas.

 

Unfortunately, Massachusetts has a Time-of-Use rate structure which is totally impractical for most residential customers. I looked into this and, to the best of my memory, learned that in addition to the cost of the T-O-U meter, the peak daytime rate is adjusted every month for the generating company's variable fuel costs and is at a much higher rate than the basic non-T-O-U rate. Because summer months require day-time air-conditioning, the higher peak daytime rate more than wipes out any savings from the lower fixed off-peak. And you must decide which rate structure you want because you cannot have multiple meters for a single residential unit.

If we had a rate structure similar to LADWP, SoCal Edison or PG&E, life would be different.

 

I'm very well aware that it's just a throttle position mapping change, however that doesn't negate the fact that in EV mode I'm not constantly "in the red" (e.g. PWR zone) on the meter when pulling away from stoplights in any kind of traffic.

I pretty much can't do anything about the super-aggressive Chicagoland drivers except to stop driving. I actually kind of hate driving the Prime in traffic when not in EV mode because I feel like I'm revving the living crap out of the engine every stoplight just to avoid a dangerous situation.

 

Yeah, we have those drivers too. I don't know what it is, but I find that when there are cars really close to my rear bumper the Prius just seems more sluggish than ever.

 

Unfortunately, I've been rear-ended in another car ignoring those drivers so it remains a risky proposition. It's wonderful when the police won't even come out to the scene (Chicago police generally don't respond to auto collisions unless someone is need-an-ambulance-hurt).

 

NJ's the same way with their TOU plan. It's like they structured it so you wouldn't choose it.