"Pretty good" PowerWall article:
Single PowerWall is sitting on a pad. The pad was selected instead of wall mount because up to three PowerWalls can be "stacked" on the pad.
Currently, non-functional awaiting BlueBonnet to turn off power, then connect to new power drop.
New BlueBonnet connection will be to the 4th box from left. The PowerWall transfer switch and controls is the 3rd box from left. Breaker panel is 2nd from left. Leftmost is the existing meter housing; meter to be moved the 4th box. String inverter for roof top PV is just the right of the window. Just to the right of that, the single PowerWall.
I just realized that there should be a 30% income tax credit associated with this deal.
Install is complete, online, working. I do not have access for monitoring or control.
Yesterday, I turned off the grid for a while to observe PV production after the battery was fully charged. So after production went to zero, I felt I had a fully charged battery going into the late afternoon.
I turned off the grid about 5:45pm yesterday and went through the night ok. As evidenced by monitored PV production, I judged I was charging the battery before 9am. Again, evidenced by zero monitored PV production, the battery was fully charged about 10:30am. I just turned the grid back on to allow me to sell production to the grid. The charging took less time than expected; it started cloudy and became partly cloudy. Not very good PV production conditions. This tells me that I could charge quite a few battery units in a not especially good production day. Other than cost, that is very encouraging for going off grid with 3-5 battery units. Of course running air conditioning will change things significantly.
I've been getting disappointing support on getting monitoring from both Tesla and the installer. I hope things will move faster after we get past the weekend; my install was completed late on Friday.
I finally hit on a way to access the gateway this afternoon. It was more difficult than it should have been because the installer told me it was using my wifi access point for internet access. It turned out to be using cell network for that access. Anyway, I now have limited and local only access to my gateway. Presented are power to and from the grid and the battery, and power from one of the PV systems. The percent state of charge of battery is also presented. Though I don't know whether that is based on 14kwh or less. I see no control. And no power to energy integration.
Now, I can see my house demand is around 5% of battery capacity per hour and is 300-500 watts. My non PV production period is about 15 hours. So my best guess right now is that I will be at about 25% of battery capacity when I start charging about 9am tomorrow. I'll not be here at that time but hope to return about the time the battery is charged and I need to connect to the grid.
Actual remaining capacity was just over 50%. I ran the bathroom heater about half an hour on the battery and used CPAP all night. Will try testing all night use of a fan though the fan is not needed in this season.
Typical of my hour by hour BlueBonnet data when running PowerWall overnight and turning grid back on only when I have power to sell. PW battery was charged back in the first couple of hours of PV production. The battery seems to charge at a maximum of 2.5kw.
The below day time over production chart represents about $2 worth of electricity if sold at $.055 / kwh. PV energy used during the day to charge the battery would be about $1 if purchased from Bluebonnet for $.12/kwh. PV energy used during the day to power the house would cost about $2 if purchased from BlueBonnet. If it lasts me 10 years, the PowerWall will cost about $3.50 / day. If it lasts me 20 years, the PV will cost about $3.40 / day. Factoring in the 30% income tax credit, the two numbers would be about $2.50 and $2.60. I did not claim the tax credit on all of the PV.
The PW has been on just a few hours short of a week. In that week, I have not bought any power from BlueBonnet and have been selling between 1.2 and 40 kwh each day. Battery charging can be completed as early as about 10 am and as late as about 5pm. Yesterday was very cloudy and resulted in the late charging completion. Minimum states of charge in the mornings have been about 30%, meaning I need to produce around 8 kwh to recharge. Since I have that 30% cushion in the battery, I can likely get through two nights that are separated by a very low production day. I look forward to seeing what happens with a string of very low production days. If I see a string of low production days coming, I will forego morning bathroom heat and will start the days with near a 50% charge. Other parts of the year, using fans and/or air conditioning will be challenging.
I STILL do not have access to settings that need to be changed. The installer has declared he wants nothing more to do with me and I'm seeking another for future PW projects. I am absolutely thrilled with the operation and potential of the PW. But, I've found both Tesla and installer support lacking.
Reflecting on using air conditioning with PowerWall.
Looking at my Curb, which monitors my room air conditioner circuit, I see average daily use during the four peak air conditioning months is about 10 kwh. I'm guessing the ~15 no sunlight hours might account for 5 kwh of that. So, the ~13.5 kwh PW might barely make it on an average day. Now, with ~17 hours non-producing hours in a day, the PW gets me through the period on 50-60% of capacity, a maximum of about 8 kwh. The shorter nights should reduce PW demand by about 1kwh. Deviations from averages certainly indicate a 2nd PW to get through the summer without altering use patterns.
"Altering use patterns" might include turning air conditioner off at night and trying to "make do" with fans.
On this date, I am about 10 days into using the PW with no power taken from the grid.
Time for an update, I suppose.
The PowerWall has performed beyond expectations.
Aside from poor support from both the installer and Tesla. I am limited to local monitoring; I've been unable to convince the Tesla miscreants in Las Vegas to associate the PowerWall with my Tesla account. That should allow me to monitor, via the Android app, from anywhere there is internet access.
I did get "installer" access to the Power Wall. That allowed me to correct a poorly set parameter. That parameter is the fraction of battery capacity reserved for a real power failure. When battery charge level falls below that threshold, the Power Wall attempts to pull power from the grid instead of the battery. Whenever battery level is above that threshold, power is supplied from the battery. The PW was initially set to 75%; it is now set to 10%.
To date, for close to two months, I could have been "off grid". I've used no power from the grid, I have only pushed power into the grid. Had I actually been off grid, all the power I've sold to the grid would have been lost.
On the typical 50% overcast winter cloudy day, I have the PowerWall battery full recharged from night time use by noon. My house PV, where the first PowerWall is located, now produces near 80kwh on a good sunny day and my energy use is around 15kwh plus whatever EV charging I do. That is, if I do no EV charging, I can sell about 65kwh to the grid. Successive very cloudy days have come close to exhausting the ~14kwh available from the PW battery. That is, very cloudy days may not produce enough energy to completely recharge. Typical overnight use, about 14 hours from low afternoon sun to a bit after sunrise, is 50%-60% of PW capacity. So, if the recharge during a cloudy day is insufficient to bring the charge up to near 70%, it may not make it through the following night. That has not yet happened though we have had long spells of very cloudy weather.
I doubt that the single Power Wall battery I have will carry me through a hot summer night requiring air conditioning. My options are to add a second Power Wall battery (at a cost of about $8k) or just use a bit of grid energy during hot nights. I don't believe I can justify the cost of a second battery.
BlueBonnet bill for period 2/12/19 to 3/13/19
The bill shows, for the house meter which has the PowerWall, 3kwh consumed and 466kwh delivered ("pushed" to the grid). The 3kwh consumed, no doubt, due to the brief periods when the PW fails to exactly match battery use with demand. At times, the grid is shown supplying about 100 watts. I apparently am not yet on the rate schedule that specifies that I am paid monthly for over production. 463kwh was added to my annual "banked" production for which, under the old rate schedule, BlueBonnet pays annually about February.