Rob's Experience with Solar Power

The Empire Strikes Back Edition

This is the second edition of my page on solar power. You can access the original here. I will be referring to the earlier version several times from this page.

The previous edition contains a number of models that assumed the EVA rate in effect at the time this page is being written. The EV-A rate has high rates for daytime use and an even higher rate for evening use. As the analysis pointed out this is highly favorable for someone that also has solar. It also discourages using batteries since if you saved (instead of sold) daytime power you would be using it at night when I could otherwise buy new power for half (or 1/4) the price.

The EV-A tariff that I am on as of this writing (Sept 2019) has been discontinued. After several false starts I am now told I will be moved onto the new EV2-A rate as of July 2020. I must admit that EV2-A was rather brilliant as they have effectively neutered my solar system by adjusting the TOD periods.

By ignoring the investment I made updating my solar system in 2017-18 PG&E has removed any ROI restriction on my purchasing a battery. Thus I am currently in the process of getting a battery from Tesla. This will minimize the amount of power I sell and buy. Almost all of my solar generation will now be behind the meter.

This new page describes the impact of this change on my models. One curious side effect (likely unintended) is that it now makes battery storage attractive (albeit at a long ROI). In a "pigs can fly" moment the demand to charge cars using solar now becomes a reality. I had left open this possibility in my previous analysis, but I am surprised it came to pass.

I have removed some of the sections that describe the 2018 performance as these are covered in the older page. The new rate system makes these irrelevant anyway.

I have had solar power on my house since 2002. I am now on my second generation system. If you get no other message from this page you should walk away with the knowledge that you can save real money with solar power. In the 2018-19 year I saved $2,100 on my bill despite having A/C and an electric car.

I switched to an electric car in 2015 (volt) and in 2018 went fully electric with my Bolt. I can power my car with 3¢/mile electricity as opposed to the 8¢/mile gas that powers my wife's Prius. I also do not have to visit the dealer every 5,000 miles to service a complex automobile. My 15,000 mile visits are mostly tire rotation. And the two cars are comparable in price.

However, while solar has saved me money and the Bolt laughs at the climb up Fremont Peak the environmental community has way over promised the impact of solar for California. With this page I hope to bring the discussion back to reality. I place the challenge of "how do I charge my car at 11 PM on Dec 21?" to the advocates of zero carbon electricity. This applies to the new San Jose Clean Energy that claims it is going to provide me green power to charge my car. While I am no fan of PG&E, SJCE is unicorns and fairies if they think they can buy the winter evening power (when my consumption is the highest) cheaper. There are only so many approved "green" sources which all of the other "green" aggregators are competing for. New large dams and nuclear power plants are unlikely to be built. I do agree that, in the future, solar could provide for our electricity for at least six months out of the year. However, simply adding more solar generation is not enough. For Solar to take over the load 24 hours per day we have to augment the grid with energy storage enough for a rainy May 2019.

Many of the images on this page can be expanded to full size if you click on them.

2002 Solar System

In 2002 we installed a 2.5 kW solar system that was on our house until being replaced last year. On a best case day this produced about 12 kWh in a day. Below is a chart of the production of that system through 2013.

Note that solar production drops to virtually zero in the winter. If We are going to power the state only with solar we would need to store the power for six months!

2018 Solar System

In 2017 we re-roofed. At that point we needed to remove the 2002 solar system. In March 2018 we were permitted to turn on our new 4.656 kW 15 panel SunPower SPR-X21-345-C-AC System. On a best case day this system can produce about 35 kWh of electricity. While 35 kWh is a lot it would take two days of best case power generation to charge my car after a 200+ mile trip. And that assumes I am not using the power to replace my normal house usage.

The remainder of this page describes this system.

This is when the system produced power on one of the best case days. The importance of time of generation will be discussed below.

The graph at the right(below) shows the production of the system during June 2018. This is pretty much best case. On a good day the system is cranking out nearly 35 kWh of power.

By winter the production has fallen. On the best case days the production is still as high as a best case day on my 2002 system. On a rainy day the cells are basically inactive.

Not All Power is Equal

This section will describe the new EV2-A.

EV2-A

The new rate system is simple. One chart for the entire week. The only thing that varies is the seasonal rate.

Note that most of the day is now off peak. Good News-Bad News. In the models I did previously I assumed that PGE would reduce the amount of NEM, but retain the price of purchased electricity. This system is more fair and allows one to purchase off peak power in the summer for use at peak. If you purchase more power than needed and your battery fills, you sell the power back. It just costs NBC (~$0.02).

The bad news is that NEM power is worth less. That makes my overall bill higher. On the other hand, what I am getting for NEM is a more defensible amount.

The rates for EV2A are similar to EVA. Note that the Part Peak rates are quite high. The drawing is scaled to show this graphically. PGE is not doing any favors since basically the day is divided into super low rates and super high.

Period	Peak	Part Peak	Off Peak
Summer	$0.47861	$0.36812	$0.16611
Winter	$0.35150	$0.33480	$0.16611

July 2020 EV2-A rate by period, season

For comparison the E-TOU-A summer rates are 43¢ and 36¢. The winter rates are 31¢ and 30¢. Note that while I am paying (and receiving NEM) at 16¢ for my solar power my neighbors are buying that power at 36¢. Who is subsiding who?

Models of Different Alternatives

Since I was allowed to turn my system on in March 2018 I have maintained a spreadsheet of hourly power purchases/sales as reported by PG&E and hourly solar generation as reported by SunPower. This vast wealth of data allow me to model several alternatives that I could realistically face. This section will talk about the various model results. Not to bury the lead, but the most favorable outcome for me is the current NEM 2.0 system with my current EVA rate schedule. This should not be a surprise since my choice of solar system was based on my having an electric car and for NEM to time shift the credits (not kWhs) to make up for costs that occur at night when the electricity is cheaper.

Current System

The previous version of this page went through all of the particulars on my actual usage.

Keep in mind that as an electric car lessor I am not only powering my house but also ~14,000 miles of driving in the car.

EV2-A

So what does EV2-A do to my bill? I anticipated it would be higher if for no other reason that most of my solar generation was now credited at half (or 1/4) the NEM it used to be. But coming up with a new estimate required going through the actual numbers for 2018-2019 and applying the new rules. Since the actuals reflect the behavior of my devices which were programmed for the old system the figure I present below has some fudges.

Off peak starts at 11 PM instead of midnight. My car, AC, and washers were all programmed assuming they could turn on at 11 PM. My use otherwise would be just lights, TV, and computer so this does not affect the conclusions
Weekend days start at 7PM again to reflect the 2018 programming
PGE Daylight Savings time correction not applied. Understanding this one took an email from their back office which initially thought was a joke until I read the tariff more carefully. This is a small change, but is noted here for completeness.

I cannot predict the effect of reprogramming my car to charge during the day. That would move more of my power usage behind the meter. Both my sales and purchases would be reduced. As such more would avoid NBC.

I repeated the calculation for what my usage would be without solar on the new rate. There was a difference of less than 1%.

Batteries

Let me first start by saying that my situation is not ideal for my usage being solely powered by the sun. My electric car uses a huge amount of power that I consume mostly at night. My solar system only produces a max of about 34kWh a day in spring. A long drive by itself requires 30-50 kWh. Anything used by the A/C, cooking, dryer, etc is extra. So there is no realistic way of not using a lot of purchased power.

Having said that previously batteries were not attractive since it did not make sense to store 24¢ power to replace 12¢ power. With EV2-A the economics change. Virtually all solar power is generated at the lowest rate. Any that is generated at the higher rates is rapidly consumed (last in - first out). So now a large solar system like mine and an electric car are a perfect match. I can now do what is shown in the Tesla pictures and collect solar energy during the day to charge my car at night.

What I did find, though, was that it was important to be able to program the battery to charge from the grid. I had to add 5 kWh of power each day in July and August due to A/C use. I added 15 kWh during each winter day. Doing so drove my premium time purchase to under $30/ year without a lot of micromanagement. If I bought too much power during a cold snap in the summer or a sunny period in the winter I just sold it back. That cost me NBC but that is less than 3¢.

The theoretical battery would still generate NEM especially during spring vacations.

Results

I have not added NBC to either the Ev2-A estimate or the battery. NBC is $109 of the Real Life figure. I estimate it would add a bit less to the EV2-A estimate since some car charging would move behind the meter. There would be some increase in the battery estimate, but I think it less than $25 so I did not run the calculation. These are based on the July 2019 rates.

	Cost
Real Life	$542.33
Cost Without Solar	$2692
EV2-A	$940.30 ($1,040)
Battery	$632

Rob's Solar Model

From these numbers some conclusions could be drawn

EV2-A, while more expensive, is not fatally so. I end up saving about $1500 per year instead of the $2100 I save now. My new estimate is that I will break even on my 2018 solar system in 2031. After that point the savings becomes real savings and not amortization.
ROI becomes the barrier to storage Ev2-A clears the way to battery storage provided you have a long enough time frame. A quick estimate with Tesla Powerwall was that breakeven was 35 years. Since PGE decided to kick me off EV-A in 2019 I have signed with Telsa to install a Powerwall.
EV2-A may reduce some of the political pressure on NEM.
Batteries eliminate the "honey, we should not be running the dryer now" discussion.
Batteries also make the NEM discussion easier. Last year I sold $1,400 of NEM'd power. Under my battery model I cut this to $156. EV2-A does not make a change other than to reduce the dollar amount I receive. The PowerWall may be more efficient in saving power. Thus I might only NEM power when I am on vacation.
As I said before Even in the worst case solar wins.

Opinion

Batteries (what we should be stressing can now stress)

Just to be clear I am using "battery" as a surrogate for "Energy Storage Device".

EV2-A has caused me to rethink much of this section. While my previous version left open the possibility of PGE changing the rates to allow charging and solar to exist at the same tariff rate, I did not take that possibility very seriously. So after having another bite of crow let me proceed.

The assumptions of the environmentalists require the use of batteries to time shift the solar generation until it is needed. Lo and behold PGE has presented a tariff that not only benefits them but also does not discourage the behavior the environmentalists want to enforce. The new barrier to battery storage is cost which is not the utility's problem.

Thanks to PG&E treating me unfairly and ignoring my updated system I now have an incentive to purchase battery storage and reduce the business I am doing with them. PG&E probably regards batteries at this point much like they did solar in 2002, a small pin prick that can otherwise be ignored. Certainly the Tesla folks think that they will not have any trouble updating my PTO.

NEM and the Current Utility Business Model

During the hearing on April 10, 2019 I heard both senators and utilities complained about how the non-users were subsiding solar users. To the extent the state gives tax credits for installing solar systems I agree. To the extent the utilities are forced to overpay for NEM'd power that is no longer true. Further since my electricity is now cheaper why are my neighbors (who are using the excess power that I am generating) also not seeing their rates go down?

In a more perfect world the utilities could provide utility level storage that could operate on a scale not possible with homeowner battery systems. We could deposit our power with the utility and buy it back at a discount. I still think that is a better model for the future. At least the tariffs no longer stand it the way of homeowners doing it for themselves.

Electric Cars

I love my current Bolt. My experience with my previous Volt was good enough to convince me to take the plunge into all electric. While the DC Fast Charging infrastructure compatible with the Bolt is not as well developed as for a Tesla, the car's native range and the available chargers allow me to travel anywhere from Monterey to Sacramento. Sadly the infrastructure is not there along US 101 south. One can hope...

I hear a lot of claims about electric cars. By allowing charging during the day and not discouraging battery use PG&E has moved closure to the future the environmentalists want.

True:

Electric cars will help air pollution in cities. Electric power can be generated by industrial size plants capable of cleaner operation than even the greenest car. Not burning gasoline means no NO or any of the other gas related pollutants.
Electric cars are decoupled from any particular means of generation. This is true. A tariff like Ev2-A no longer precludes charging when solar is easily available.

Still I rely on purchased power to charge my car. The current grid relies on fossil fuels overnight when I do most of my charging. CCAs like San Jose Clean Energy claim to provide power from low carbon sources except there are only a fixed amount of "approved" sources available. Zero carbon sources such as nuclear and hydro could fill this need but are opposed by different environmentalists than are concerned with carbon.

Of course if utility level solar increases along with energy storage then this could change (at least in the summer)
Electric cars should be charged by solar This one has moved (at least partially) out of the hokum category. Lo and behold that is now possible without incurring a penalty to either directly charge or to use stored power. Of course, on an annual basis this is more difficult due to that nasty problem called "winter".

Hokum:

Corollary:Electric cars reduce greenhouse gas - This one I still maintain is false even if I install batteries. My car being in California is powered by natural gas (with a touch of nuclear and hydro thrown in). A customer from Ohio could say he had a coal powered car. Every one claiming solar is in the mix is making the mistake of using the daily numbers. They are not considering that cars are mostly charged at night (at least mine is). At night only the base generators are running (with a touch of wind).

With the coming Tesla Powerwall this will change somewhat. I will now be time shifting my solar generation and some of my car charging may now be done with saved solar power. However, much of the charging will remain purchases of natural gas generated electricity (since I have no interest in taking a sip of the CCA koolaid).

My test for a zero carbon future remains "how do I charge my car at 11 PM on December 21?"

So we now have enough solar power that at least in the summer the realities are changing.

I did not buy into the environmental arguments (at least not completely). I drive an electric car because it is quiet. I also expect that it will prove to be more reliable. And it climbs hills like they were not there (and loves to go down them). While it requires more planning for a long trip, only travel south on 101 has proved to be a problem. I fully expect to put 15,000 miles on the car each year.