To Charge or not to charge- that is my question

That’s a rather curious calculation there! You are probably getting a much-higher-than-average rate for energy sold back to your utility (or perhaps you’re not really getting that much back).

I personally don’t, yet, have home solar, but from what I’ve heard from colleagues at work who do, Austin Energy doesn’t pay them as much for energy they supply to the grid as they pay AE for energy they receive from the grid. Of course, they pay quasi-nothing (i.e., other than the cost of the panels) for energy they use directly from their panels.

In either case though, my question is *time of day* you charge. I’ll assume you don’t have a large battery, and that you charge after peak-solar hours, e.g., after you get home from work — say 7PM at the earliest. (You’ll probably get best battery conditioning charging right before you leave.)

If indeed both of those assumptions are true, then you’ll be charging *from the grid* and *not* from your panels. In that case your P.Prime will be at work the entire time you’re selling energy to your utility. The situation of diverting energy to your car that could be sold to the grid, would rarely ever even come up.

That being the case, then it’s just a question of $/mile from the grid vs. from gas. In my case, those numbers work out to around 2.5 cents/mile from the grid vs. around 4 cents per mile from gas.

Possible minor nit in your calculations: I at least am not able to charge 6KWh into my P.Prime (more like 5.5KWh), and I’m seeing about 4.6 miles per KWh, so guessing your estimate of 25 miles per 6KWh is a little pessimistic.

(Wow, did I understand you correctly to have 180 mile daily commute?!)

 

I think you are simplifying the calculations too much. Gas price may not stay as low. The electric company may not keep paying you the same amount for the electricity you generate. AND unless your solar panel is generating in excess of what you use in your household, you can not cash in the total amount of $0.31 / kWh. If your household uses more electricity even without charging PRIME, your potential GAIN is the difference between what you usually pay for the electricity and what you get paid for the electricity generated. What is your rate for electricity purchase?

 

I can tell you out here in the Bay Area that PG&E pays $0.04 per kWh sent back to the grid at true up time.

We are going to be slightly positive at true up, but now that we have a Prime I will be charging at home, I’ll need a couple more panels .

That might be the rate they would charge if you used in excess rather than sold in excess. I believe that’s close to what PG&E charges out here if we didn’t size the array correctly and they supply us power.

 

Again, I think the main question is time-of-day: If your usage of a grid-tied home-solar system is typical, your panels will be generating next to nothing *at the particular time of day* when you’ll be charging your P.Prime.

That being the case, it won’t matter now many cents per KWh the utility pays you, because at the time you’re charging, virtually all of it will all be coming from the grid anyway. So then, it’s just a question of $/mile charging from the grid vs. $/mile from gas. For me at least, that’s 40ish% cheaper from the grid. (Well, that plus all of the other advantages of EV driving — quicker gas-pedal response, lower noise, etc.)

 

Mark I like the way you simplified the cost of gas vs electric. It make comparison of cost for fuel source very easy. If i understood your calculation right:
Cost for 25 miles on gas = Price of a gallon of gas/2
Cost for 25 miles on electric = Cost of Kwh x 6 (6.3 if someone wants to be exact?)

While this may not be perfect and peoples individual situations are certain to vary it seems to be a quick and simple way to determine and compare cost.

I appreciate you sharing this with us. We are determining now if we want to buy a plug in model car and want the decision to be heavily weighted on the economic factors. I have seen many complicated formulas and equations that attempt to take in variables. I believe your way is simple, straight forward and immediately gets you in the ballpark for cost comparisons.
Understanding there may be some confusion with your cost of energy sold back and that is what people are discussing - your first electric bill or a quick call to your utility may sort that out.

I notice that the 2019 Prime spec is 8.8 Kwh I assume the usable part of this for ev mode is 6.3 Kwh and the rest is a reserve for starting the engine etc.

Your homes solar array looks awesome. It looks like your family is well on the way to some Energy independence from the Utility companies.

 

Online, I'm seeing that NJ is among the most generous states in the nation for solar incentives. They get net metering at full retail rate, not wholesale as some other states use. Though the sample rates shown here are much lower than OP lists. We'll need more information, to make sure that other charges are not being rolled into that $0.31 / kWh statement.

For someone comparing strictly on the basis of $/mile, this 'time of day' issue matters only of they have 'time of day' metering. For flat rate metering, time of day doesn't matter.

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In my state, I have retail net metering forever, plus a solar credit on gross production that sunsets in June of next year. Net metering doesn't pay for excess production beyond my home's use (I do currently have a small excess), and the excess defaults to the utility after a year. More reason to acquire a plug-in car ...

Bad news / good news story: Apparently, the production credit program is closed because it has already hit the legislated cap. New installations still get net metering, but not any production payments because so many of us already installed solar systems .

 

i'm amazed at how many plug in and solar owners aren't in it for the environment

 

SIX hours of commute time 5 days a week!!!! Dude, get a closer job or move!

Per the link from @fuzzy1 you are getting paid the same as you are being charged and time of day doesn't matter (though @mr88cet was smart to consider that possibility) -
"Jersey Central Power & Light’s net metering rates are determined by multiplying the amount of net metering credits produced annually by the current retail rate, which is currently 9.4 cents/kWh. Credits are applied to future bills until used up and extra credits are credited to the customer account at the end of the year."

You should be able so see what you are being paid and credited on your bill each month.

BTW, 9.4/kWh is cheap, it is over $0.17 here. Plus the daily charge for the privilege of being connected to the grid and a dollar for low income customers.

Vermont's system is like @fuzzy1's. We are credited what we are charged, credits are by month and if you haven't used a month's credit within a year, the power company gets free electricity from you. We also have a 10 year incentive (the only incentive available from the state) that pays $0.05 for every kWh generated whether the power company sees it or not. Until last year the credits could be used on any part of the bill. Newer installations are getting screwed because the credits can't be used for non kWh based charges. That means the newer people are paying a minimum of $15 a month cash to the power company no matter how big an array they installed. This is due to state legislation, not the power company.

Consider the price of the car and your tax situation. With the federal tax credits and regional Toyota "cash back" money, you might be able to buy a new, left over, 2018 for less than a non Prime Prius with equivalent (or fewer) features. In that case your purchase is positive on both the environmental and financial metrics.

 

I cannot believe the price, it might be $0.031/kWh?

If it is true, then you can invest on solar panels and it would pay itself in 4 years

 

I would not believe $0.031, very few places in the country have retail prices that cheap, essentially all in fully hydroelectric districts. Remember the NJ has net metering at retail rates, not wholesale.

I'm not sure that anyplace has such good terms for significant production excess beyond what the house consumes annually.

 

Bruceha-2000 - thank you for your response. I in fact almost traveled recently to New York to buy a 2018 Prime but it sold as I was interacting with the Dealer. One issue with the new Prime is that the discounts you mention are indeed regional and far from our area.

Our local Toyota Dealer has told us that distribution of the new Primes is also regional and at the time we talked to the Dealer the Southeast Region had not been granted any allocation of new Primes but hoped that would change soon. The Dealer mentioned at times they do trade allocations with different Dealers but at this time their inventory was selling well and they would not be willing to use any of their inventory for a trade in allocations.

This is a common issue that many people experience in areas that are not in the Northeast or California. It is not unique to Toyota as we were also looking at the Kia Niro and the Dealer said the only way a person in our area could obtain a Niro Plug in was for the Dealership to locate and special order the vehicle to be shipped to the Dealership. He said our area receives no allocation of these vehicles.

One issue plug in vehicles have is they seem to be a niche vehicle that if you live in certain areas they are not readily available and in some cases not even able to be ordered. There is even a thread started on our Forum called 'Prime sighting in the wild' that implies how rare it is to see these vehicles.

 

The main issue is that Toyota allocates based on vehicles of that model sold the previous year. They allocated Primes to CARB states forst so they naturally get more this year based on last year's sales.

It is unfair to those dealers who could sell many more if they were permitted.

 

Sad state of affairs! They probably figure all the "country folk" only want pickups, why carry cars that get great mileage. I'm on a couple of other forums and yeah, no one gives a cr@p about MPG. I can see it if you have only one vehicle and need a PU that gets 15 MPG. But lots of people are not in that situation.

I THINK the Primes in the wild thread was started back when the car had just come out in 2017.

Sales based on last year's sales is a poor metric. Maybe they should consider doing some market research.

 

or, they are too costly to toyota to try/want to sell more

 

My point is that he’s most likely going to be charging at 7PM or after, and their panels aren’t going to be generating any power during that time frame. So, it doesn’t ultimately matter for how much they can sell a KWh, because during the time frame he’ll be charging, their panels won’t be producing any power to sell.

 

Without time-of-use pricing (many of us still don't have it), and with true net metering, that time shifting is irrelevant.

Time of solar production, and time of home consumption, don't figure in to basic net metering. The only things that matter are the net- and production-meter totals at the end of the billing cycle.

There are (or were) some net meters that were blocked from rolling backwards. For those, timing to production and use do matter. But OP doesn't have that.

Similarly, time of use pricing bollixes this analysis.

 

There are these amazing things called batteries that can save the power so it can be used later.

 

Yes, as I mentioned, I’m assuming he has no batteries. Most grid-tied systems don’t, since avoiding batteries is usually why people grid-tie a system.

Of course if he does have batteries, then he’ll lose 15-20 percent efficiency to charging and then discharging those batteries, compared to charging directly from the panels. Not a huge deal, but still part of “the equation.”