When to choose advanced over self-powered mode

When to choose advanced over self-powered mode

I'm a california PG&E customer, 5.9 kw system with one powerwall 2. Bill before solar $275 month.
I'm able on most days to be 100% self powered, while giving to grid. PG&E has peak time from 4-9 pm in my area.
Just wondering what others have done, do you just look at your monthly bill/usage and then change setting and compare?
Thanks | April 23, 2020

I suspect on cloudy days, you might try and save a little by switching to advanced and save the battery power for the peak rate time, but not sure it's worth the bother. I'm also in the PG&E service area. So far, I just leave it on self-powered mode. It's rare I run out of PW power before 9 pm, even using the range and microwave for dinners. Remember also when you are putting power into the grid, you'll be credited when pulling it from the grid later and credits last for the entire year. Most of these systems are sized to get you close to a net-zero over 12 months - although PG&E has meter charges and a few other charges you can't get away from short of going grid free.

gregbrew | April 23, 2020

I'm with SCE, in coastal So. CA. 5kW and 2 PWs. I'm still on residential tiered, because it's the cheapest for me when I consider all of the daily fixed fees.

Because I applied for an SGIP grant, I'll be required to use the batteries a specified number of hours per year during peak times between 4PM and 9PM. In anticipation of getting the grant, I've already changed to "Custom", and have set the Peak time to between 4PM and 9PM, with a 30% reserve, even though I haven't received the check yet. I noticed right away that I wasn't using nearly 70% of my battery between 4PM and 9PM, so I extended it to midnight. Now, I'm using about half of my battery capacity each day. Of course, that will change with season. I'm not extending in the other direction (before 4PM), because there's already an over-abundance of solar pumping energy into the grid from after sunup to 4PM. I think I may extend Peak to 6AM for the Spring, Summer, and Fall, and let the TEG shut off the battery at 30%, whenever that happens, over night.

Tesla-David | April 23, 2020

I live in Edmonds, WA and we operate our two PW2's in self powered mode year round, and are able to operate in 100% self powered mode for ~9 months of the year. Our annual electric bill with 13.2 kWh solar PV and 2-PW2's was only $180 last year, and we are exporting 50+ percent of our solar back to grid. We do not have TOU up here so there is no advantage to changing out of self powered mode to take advantage of lower utility rates like @sonoboy. We only rely on grid energy during mid-November - mid Feb, when there is insufficient solar PV to charge our batteries. After almost two years with our PW2's we are extremely happy with their performance to complement our solar PV.

sonoboy | April 23, 2020

Thanks for the replies. Currently in my setup I have my reserve set to 1%(because i figure in reality with the built in safety margin by Tesla, its 6%)..Powerwall and solar run house from about 6 pm on till solar picks up at 7am. I have a morning residual reserve of about 5-10% when coffee starts and solar starts to kick in. Most of my powerwall energy is used by a spa pump/heater pulling 3.3kwh for two hours every evening. I like being 100% self powered, and thought that's where i would save the most money(like $250 mos.?). My average giving back to the grid is 10kwh mostly during 2-6 pm. No car charging happening currently. Maybe i dont need to go on the advanced time base control unless i want to increase my morning reserve?hmm..

Tesla-David | April 23, 2020

@sonoboy, it sounds like you are doing quite well with your current solar PV + 1 PW2 setup. I am impressed that you are operating with little/no grid energy, so I personally see no need to modify your setup. We also charge two Tesla's (MS and M3) off our system but we have larger solar array and one additional PW2. We have to stagger our charging during the solar day to keep from depleting the batteries. We have no problem doing that during this time of the year, but it becomes more of a challenge as the solar diminishes in the Fall/Winter. Based on my two year experience, I probably should have added one or two additional PW2's to provide that little extra buffer against rainy days where solar does not allow us to fully charge up our PW2's. We are currently in a rainy day scenario, and my batteries depleted down to my minimum set at 5% last night, but are charging back up today. I see nothing wrong with your 1% setting to maximize your output.

sonoboy | April 23, 2020

@Tesla-David, Thanks. I'm lucky to have started my system during a good solar time of the year and good coastal south position. I will continue self-powered and re-evaluate for winter months where i may not be able to fully charge the powerwall...that maybe the time to go to the advanced balanced mode to ensure maximum powerwall charge for evening time.. When the Volt arrives I will most-likely have to change the scenario. Might be able to get away with Charging during the day with excessive solar on the weekends and plug in free for a few hours at work on weekdays. If not then i would be considering an additional powerwall as well.

gregbrew | April 24, 2020

Do understand that conversion losses when you cycle your battery is about 10% between energy in and energy out. So if you cycle the battery often, you'll need to include that 10% loss in your calculations.

sonoboy | April 24, 2020

@gregbrew, thanks..yep .. so basically that means that PG&E gets 10% more energy than power wall feeding the house right? just accept that's the price to pay when dealing with the sun :)

gregbrew | April 25, 2020

Yup. PV-only installations feed the grid with few losses, and use it for the pseudo-battery. With a PW, you feed the PW with a 10% round-trip loss. It's usually cheaper to just use the grid for "storage", but it does depend on local e-energy tariffs. IMO, the biggest liability of using the grid for "storing" excess production is that if the grid goes go down. I'm amazed how many PV-only homeowners don't understand this until the first time their local grid goes down.

I look at PWs as very expensive "insurance" to protect whats in my refrigerators and freezer. | April 25, 2020

And the PWs allow us to keep on posting using our PCs when power is out, assuming the Internet stays alive:)

Jones | April 27, 2020

Also NorCal PG&E. Powerwalls addition to our existing solar were approved by my significant other based on multiple grid failures every year (fire, earthquake, wind...). Also on the 4p-9p peak pricing (and have a Model 3). Have tried each of the various settings during both winter and summer except backup only. Settled on advanced cost saving with 25% reserve as the best combination of efficiency, safety for unexpected outages and ROI. Getting a check from PG&E for just under $1,000 for my annual true-up next month

doconbhi | April 27, 2020

My TOU situation is different. I live on an island of 7,500 with what I guess is called a Community grid. We have a 12MW oil fired generator with no connection to the other islands. Our rates are about twice Oahu and Maui so rooftop solar was enthusiastically embraced. The utility became saturated and MECO put a moratorium on new solar. I waited 3 years for approval to install my system. My system is awaiting final MECO approval so the following is speculation.

Current 24/7 rate is about 37¢/KWh. TOU Peak rate 46¢, Off Peak 25¢/KWh. Peak rate is 1700-0900 - low/no solar generation time. If my PW is fully charged at 1700 I should be able to get to 0900 with a 20% reserve. We have frequent enough power outages that the Reserve is really the driving factor for getting the PW.

We have mostly sunny days but overcast generally comes for 3-5 days in a row.

How "smart" is the Gateway? Going with TOU seems good if, come rain or shine, the Gateway calculated a level of charging that would give me a fully charged PW at 1700. If it is not so smart and starts high rate charging at 0900 without considering my usual daily charging from solar [4.8KW array] I could end up buying 25¢ power in the AM and selling back 17¢ power in the PM.

Any thoughts on self-powered or Advanced for me?

Off topic - I use a Galaxy Tab 2 for the app. It does not rotate to Landscape view. The graphs would be a little nicer for my old eyes in Landscape. Anyone else think that would be nice?

Jones | April 28, 2020

@doconbhi - empirically, the advanced control and balanced option should work best for you. The primary "goal" is to minimize cost, but this mode cycles the battery much more frequently and to a deeper extent than the simpler cost saving mode. You will need to set a decent reserve for the cloudy days and that will be dependent on your usage as well as your solar production.

Tesla-David | April 28, 2020

@doconbhi, if you read my summary above, I can effectively operate in self-powered mode for 9 months of the year in Edmonds, WA. Based on your overview and where you live with more balanced solar production year round, I see no reason why you would not operate your Solar PV + PW2 battery in self powered mode and I believe you could operate effectively for 12 months of the year. We only need to supplement our solar during winter when there is insufficient solar here to fully charge our 2-PW2 batteries. I don't think you would have that problem, so worrying about advanced settings for TOU access would not be needed IMHO. My wife and spend a lot of time in Hawaii, and if we were to buy a home and live there I would be off grid with solar PV and PW2 batteries.

sonoboy | April 28, 2020

I recently purchased a amazon fire hd8 refurbished unit from amazon to monitor the Power app....I too notice that it doesn't allow you to tilt the unit and get the widescreen view... It also doesn't have that option on my android phone... Maybe that's something else Tesla could work on for the next update..?

Tesla-David | April 28, 2020

We monitor our Powerwall's and cars (MS and M3) with the Tesla app on both our iPhone and IPAD, and the graphics are represented only in portrait mode and I am generally satisfied with the portrait graphics represented. Not sure how Landscape would improve what we are seeing much on our Apple devices IMHO. I am not familiar with the output of Tesla app on Galaxy Tab 2 so can't really comment on whether it is different than Apple devices.

sonoboy | April 28, 2020

@doconbhi , I agree , nice for older to guys to see from across room lol

doconbhi | May 1, 2020

@ Jones @Tesla-David Good responses both but think I need to add a bit more info. Electricity is so bloody expensive Government and a few businesses are the only ones who have A/C. The rest of us have everything open year round - min. 70ª winter morning and 90ª+ summer afternoon with 65% humidity. Not as "tropical" as the brochures would like to portray. Think living outside with a roof for shade. Other than when I do laundry or a batch of cookies, my usage is fairly consistent throughout the day. I have solar hot water.

TOU Peak rate 46¢, Off Peak 25¢/KWh. Peak rate is 1700-0900. 16 hours of peak rate and I average 0.7kWh/hr. With a fully charged battery at 1700, I would have about 2kWh left at 0900. Not much wiggle room and about 3 hours backup. We have power failures often enough that I am more interested in the battery backup than being green.

If the Gateway would top my battery off for full charge at 1700 TOU could work. Do you think the battery will charge from solar and the grid at the same time?

Balanced solar production year round: Most people do not realize how far south Hawaii is - 21ª North Latitude. Tropic of Cancer is 2ª north of us, Tropic of Capricorn 45ª south. An incredible change of sun incidence angle during the year. There is no "good" location year round for panels. My installer has constantly fallen short of expectations and I don't know value of Aurora computer evaluation software but calculated monthly output shows 450kWh in January and 700kWh in July. I have averaged bit over 500kWh per month for year before solar installed.

I will play with it using Advanced Balanced and Self Powered before applying for TOU rates but thought maybe someone here had studied on it and had something more than my idle speculation. | May 2, 2020

@doconbhi - Not sure which island you're on. My brother on Maui can't get TOU so the rates are quite high all the time. He now has solar, and with the extra state rebates, it was a no brainer. Payback I think is less than 3 years.

As far as I can tell, in the USA you cannot charge a solar/PW system from the grid except for the Stormwatch feature - i.e. Tesla identifies a major weather event and allows grid charging. Charging from the utility is not a Tesla issue, but one the Utilities seem to have control over. In the UK for example, the Powerwall can charge from the grid.

Tesla-David | May 2, 2020

@doconbhi, When we downsized, we also made a commitment to rid ourselves of all fossil fuel energy sources, so we got rid of our natural gas furnace, water heater, and replaced both with electric heat pump and heat pump water heater. The heat pump works very efficiently to both heat and cool our home (when needed), so that might be something to consider where you live, if the heat and humidity bothers you. Based on our trips to Hawaii, and discussions with home owners there with solar PV, I see no problems being able to produce enough solar to satisfy your home needs. When my wife and I generally head to Hawaii (December - February) we never use AC and have been comfortable with open windows and ceiling fans. is correct about not being able to charge our PW2's from grid except when Stormwatch is activated. We found it very useful last winter during snow storm.

FYI, I watched an interesting episode on Tiny House Nation about two women building a Tiny Home completely off grid on the Big Island.

doconbhi | May 2, 2020

Thanks. Not being able to assure a full charge at 1700 could have me buying Peak rate to get through the night. If I believe the Aurora evaluation, 4 months out of the year solar alone will not fully recharge my battery even on the good days. TOU does not seem the play.

I'm on Molokai and served by MECO, same as your brother. Odd he can't get TOU because it is listed as available on Maui here:

Pay back is longer here even with the higher cost of electricity compared to Maui. Extra Young Bros. shipping and a Maui crew here for 5 days. Fed credit is 26% this year, was 30% last year. With no A/C I'll only save about $175/mo. My payback would be 6 years without the PW, 10 with PW if I get the minimum $25/mo. bill each month. At 71 years old payback was not the driver, I have a very expensive backup so I can watch movies when the grid goes down and a new toy to monitor.

Jones | May 2, 2020

The time based controls fundamentally push your solar output into the batteries and to the maximum possible charge during off peak times (daylight) and then move your house load to full battery support during peak (night). It simply automates your intended run from battery during peak time and then recharging the battery during off peak to get ready for the next peak use period. The self powered setting would be similar in your case - because your peak is essentially night-time.