Solar and power wall 3 quote.

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Minister of Fire
Jan 19, 2019
6,175
SE North Carolina
I got quote for solar incoming. 10kw system with a Powerwall 3 batter backup. Sticker is $42k with an out of pocket of $20k after duke and federal credit. Cost does not include a tree removal but does include a new main panel. Offer includes 12 months same as cash op to $30k.

I have not read any fine print but will. The site meeting was last evening.

I’ll make a spreadsheet today. Duke had to approve the project in order to get their money and connected. They take applications starting Friday so this likely needs a decision by then or Monday.

Also not included was a monthly credit of 52$ for participating in their energy wise program where they can draw down my battery 35 times a year to 20%.

Basically with net metering for 15 years, Tesla Charge on solar, and the $52 credit it’s hard to pass up. But again I will run numbers tonight.

I could save $$ by skipping the panel upgrade by then I don’t get AC and hot water backup. Panel may be original. Powerwall 3 has built in inverter so it’s a string install not Micro inverters.

This will be a cash purchase. Means indeed to wait on a new van another two years probably.

Is this deal too good to pass up??
 
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The combo of a battery and net metering seems weird. Net metering is using grid as battery. (Unless you have frequent and problematic power outages, and the $625 per year pays for the batty- which it doesn't?

String inverter sucks unless you have all panels on one side of the roof and no chimney shading...
 
The combo of a battery and net metering seems weird. Net metering is using grid as battery. (Unless you have frequent and problematic power outages, and the $625 per year pays for the batty- which it doesn't?

String inverter sucks unless you have all panels on one side of the roof and no chimney shading...
Battery works basically as a personal backup (unless I enroll in time of use billing and or energy wise program).
Duke pay for most of thr battery before 52$ credit. My worry is that the credit only counts to the current bill cycle. In which case summer probably would not carry a bill.

South ish facing roof tree will be removed. Peak production shading not an issue might be some in the winter after 3pm. Need to reall sight that in.

Solar and power wall 3 quote.
 
Okay, if the battery is paid for before your $52 a month earnings, that's fine (still only useful during power outages).

If your solar installer goes by the satelite pics, get another one. They are hacks and their numbers don't mean squat. Ask them at what angle the top of the tree is when viewed from the bottom of the lowest mounted solar panel. If they don't know, they're bullshitting you.

There are multiple trees in the pic, so cutting one down doesn't mean much. The sun in winter is low on the horizon...

*In particular with a string inverter* you need to have folks on the roof placing fisheye lens cameras at each corner of the proposed array, superimposing summer and winter solar paths on the field of view at those corners to truly calculate your production.
Did they even take into account the string inverter in their calculations?
 
Price before rebates sounds in the ballpark. $3 an installed watt plus 10K for the battery. I think in low labor cost areas of the country it could be high as equipment prices have dropped. I am not a fan of microinverters but if you need them to be able to access the battery its not a show stopper. They do tend to have a higher failure rate than optimizers but the failure rate isnt that high to begin with (rule of thumb from pros in in the 3 to 5% range in the long run for micros.

I would negotiate a flat fee for microinverter replacement in the future. The fail out of the box but just as many just have shorter lifespans. Installers really do not like doing it as they need to dispatch a tech to climb on the roof, remove the panel, swap out a "box" and then put it all back together. It will eat up half a day that they could be installing a new system.

Given the generous incentives in NC I would pull the trigger sooner than later as many incentive programs are getting scaled back. The battery will not get a lot of use, I tell most folks leave out the battery and invest in $600 back up generator unless there are frequent power outages. My guess is time of use will become non optional soon in many utilities but when it does my guess is that capability should be added.

One thing to consider is negotiating a long term cost to change out a microinverter. The rule of thumb long term failure rate is probably in the 3 to 4% range. Its a PITA to swap them out as the panel needs to be removed and replaced. Installers dont want to be out on warranty calls so in few years if they are business they will make sure to charge thru the nose to do a replacement.
 
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Price before rebates sounds in the ballpark. $3 an installed watt plus 10K for the battery. I think in low labor cost areas of the country it could be high as equipment prices have dropped. I am not a fan of microinverters but if you need them to be able to access the battery its not a show stopper. They do tend to have a higher failure rate than optimizers but the failure rate isnt that high to begin with (rule of thumb from pros in in the 3 to 5% range in the long run for micros.

I would negotiate a flat fee for microinverter replacement in the future. The fail out of the box but just as many just have shorter lifespans. Installers really do not like doing it as they need to dispatch a tech to climb on the roof, remove the panel, swap out a "box" and then put it all back together. It will eat up half a day that they could be installing a new system.

Given the generous incentives in NC I would pull the trigger sooner than later as many incentive programs are getting scaled back. The battery will not get a lot of use, I tell most folks leave out the battery and invest in $600 back up generator unless there are frequent power outages. My guess is time of use will become non optional soon in many utilities but when it does my guess is that capability should be added.

One thing to consider is negotiating a long term cost to change out a microinverter. The rule of thumb long term failure rate is probably in the 3 to 4% range. Its a PITA to swap them out as the panel needs to be removed and replaced. Installers dont want to be out on warranty calls so in few years if they are business they will make sure to charge thru the nose to do a replacement.
The power wall has a built in inverter so micro inverters are out for all power wall 3 installs.
Okay, if the battery is paid for before your $52 a month earnings, that's fine (still only useful during power outages).

If your solar installer goes by the satelite pics, get another one. They are hacks and their numbers don't mean squat. Ask them at what angle the top of the tree is when viewed from the bottom of the lowest mounted solar panel. If they don't know, they're bullshitting you.

There are multiple trees in the pic, so cutting one down doesn't mean much. The sun in winter is low on the horizon...

*In particular with a string inverter* you need to have folks on the roof placing fisheye lens cameras at each corner of the proposed array, superimposing summer and winter solar paths on the field of view at those corners to truly calculate your production.
Did they even take into account the string inverter in their calculations?
They have lidar data in the model that guesses what returns are individual trees. I do want have the three remaining trees sighed in. Since I have a walkout basement the topography is in my favor.
 
okay, lidar is good. A fish-eye camera is better.
I asked my installer for the pics they took. Illuminating!

Regarding microinverters vs string inverter, if your exposure is truly even at every hour of every season, there may be a disadvantage.
But going by their failure rate without considering the failure rate of string inverters (which take **all** panels out of action until the inverter is replaced, "multiplying" a microinverter fail rate by the number of panels you have...) is not a good comparison.
I.e. if you have 20 panels, the fail rate of a string inverter should be 0.03/20 = 0.0015, or 0.15%, to be equal in lost panel hours due to inverter failure.
I wonder if their fail rate is that low...

For what it's worth, between my and my friend, we have 42 panels now for 6 years. Enphase microinverters.
That's 252 microinverter-years. Times 3% fail rate (lower estimate above), means we should have had 7.5 of them fail.
None yet. Of course that's anecdotal, not proof.

Yet I wonder if peakbaggers data are pertaining to older microinverters?
 
I tried that site, and it told me I have 1000 hours of full sun per year on my roof. Which sounds about right for my arboretum of a yard.
 
What are the odds they are going to draw your battery down on the days you’re going to need that power? It seems like they would only need your power when they can’t supply it.
 
okay, lidar is good. A fish-eye camera is better.
I asked my installer for the pics they took. Illuminating!

Regarding microinverters vs string inverter, if your exposure is truly even at every hour of every season, there may be a disadvantage.
But going by their failure rate without considering the failure rate of string inverters (which take **all** panels out of action until the inverter is replaced, "multiplying" a microinverter fail rate by the number of panels you have...) is not a good comparison.
I.e. if you have 20 panels, the fail rate of a string inverter should be 0.03/20 = 0.0015, or 0.15%, to be equal in lost panel hours due to inverter failure.
I wonder if their fail rate is that low...

For what it's worth, between my and my friend, we have 42 panels now for 6 years. Enphase microinverters.
That's 252 microinverter-years. Times 3% fail rate (lower estimate above), means we should have had 7.5 of them fail.
None yet. Of course that's anecdotal, not proof.

Yet I wonder if peakbaggers data are pertaining to older microinverters?
Can’t the the remaining trees until I remove the one next to the house;) I just got off the roof. Those trees will be an issue in winter afternoon /evenings.

The price of the power wall 3 at $13k for a 13kwh back up and able to deliver 11kw to the house with 148 startup amps. It’s a no brainer to skip the micro inverters. Panel strings and placement will be important and makes design more involved.
What are the odds they are going to draw your battery down on the days you’re going to need that power? It seems like they would only need your power when they can’t supply it.
My understanding is that if the grid goes down my automatic disconnect will disconnect me so they can’t draw my battery. If grid is up I don’t need battery backup. I’m sure it’s more detailed than that.
 
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Well, the first two rounds of Enphase failures really upset the statistics. Like any product folks always hope "this time will be different" and I hope yours are but on various forums solar pros typcially state the 3 to 4 % long term failure rate. I actually have 4 of the problematic 195s that I bought used that had the reputation of failing at a high rate, but they are not mounted on the back of a panel on a hot roof. I feel that environmental factors are going to cook a complex electronic product faster sitting on the backside of a panel on hot roof than a string inverter bolted to concrete wall in the basement. If I use my own experience, my three string inverters of various ages from 15 to 25 years have not failed.
 
I have the IQ7plus.
We'll see.

Your three string inverters (at say 60 inverter years) still need to go a few decades to reach the same panel hour disruption as a 4 PCT fail rated micro inverter. Assuming you have about 20 panels.
 
Well, the first two rounds of Enphase failures really upset the statistics. Like any product folks always hope "this time will be different" and I hope yours are but on various forums solar pros typcially state the 3 to 4 % long term failure rate. I actually have 4 of the problematic 195s that I bought used that had the reputation of failing at a high rate, but they are not mounted on the back of a panel on a hot roof. I feel that environmental factors are going to cook a complex electronic product faster sitting on the backside of a panel on hot roof than a string inverter bolted to concrete wall in the basement. If I use my own experience, my three string inverters of various ages from 15 to 25 years have not failed.
Powerwall will get bolted to a south facing exterior wall. It will need some shade
 
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Not a lot of choice with Powerwall's (batteries in general) , many codes now preclude them from installation inside a dwelling unit due to fire risk. Even though most batteries are now the far less flammable chemistries there are still potential risk issues associated with storing a lot of power in small box. The DIY battery folks on the DIY Solar Forum are frequently posting their failures. With the new battery chemistries, they tend to be bad electrical connections but a few of the folks have burned their houses and battery sheds down.
 
BTW make sure the quote includes a high quality household surge suppressor ont he incoming line and its generally recomended to install one on the line coming in from the PV array. The one I have installed in several locations is a Midnight Solar SPD. There are numerous cheaper examples out there but the Midnight Solar has a lower than typical clamp voltage which means a better chance of sensitive electronics might survive. If someone has home shop with equipment capable of surges, its worth installing a SPD between the inverter and the main panel.
 
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Here is the tree that has to go. And a wide angle of how close the pines are to it. Some good fire wood and slabs there.

Solar and power wall 3 quote. Solar and power wall 3 quote.
 
Bummer! Nice shade tree
 
Bummer! Nice shade tree
Yeah but it loses leaves twice a year. And clogs the gutters every 3 weeks. The combination of leaves pollen acorns and pine needles will clog any gutter guard. I’m a bit sad. It blocks all winter sun from all but one window. It’s a 2-3k removal job. That’s at least 10% of my out of pocket cost. A significant expense. It needs a good trim now. It’s not good location other than pm shade on the patio.
 
Be real careful of the company you deal with- most are- as the govt. money dries up they go out of biz and you are hung out to dry. Grid power supply companies have it figured out for them to make money off of you one way or another. ( ya I am a bit negative, but only because of the practices I see and hear about) I am in WI , I have had a couple quotes- Too High. those were roof mount which i do not want any way. Ground based array is more practical for me ( i have the land). just north of me (Brownsviile, Waupun area ) they are installing mutiple Hectors of solar arrays, ground based( 1ha = apx2.45 acres) This in addition to the large windfarm system already here. ( guess who is paying for it one way or another) Beaver dam solar project, is the name it goes by.
 
Question for the solar geeks….

Powerwall has lots of settings. Would you trust the installer settings and leave them alone and trust the white box and installer or explore them and learn the whole manual to really understand how the system is operating and what controls I have?

Given the PW3 has a 10 year warranty, do you save battery cycles and use it mainly as a battery backup or use the battery daily to maximize savings? (This answer probably depends on your net metering arrangement but let’s ignore that).
 
Not a solar geek here, but installers just want to get the job done and move on. Learn your system and be prepared to fiddle with it if you want the most out of it.
 
Regarding its use: is it worth having a $10,000 insurance or is it an investment that will give savings?

Insurance is rarely used, except in catastrophes.

Using it to gain savings STILL allows you to have it as insurance if catastrophes happen.
The performance warranty is not worth much if you keep its cycles low anyway.

So I'd use it in principle.

However, if your savings are essentially zero because of your net metering, I'd just keep it as insurance. Yu indicated the utility is paying for it thru monthly $$ meaning your utility gave you free insurance (and you use the grid as battery).
 
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Question for the solar geeks….

Powerwall has lots of settings. Would you trust the installer settings and leave them alone and trust the white box and installer or explore them and learn the whole manual to really understand how the system is operating and what controls I have?

Given the PW3 has a 10 year warranty, do you save battery cycles and use it mainly as a battery backup or use the battery daily to maximize savings? (This answer probably depends on your net metering arrangement but let’s ignore that).

There is a lot of area between the options you give on the setting. I would at the least review the troubleshooting section and understand a few basics of the system. I would also simulate a power outage a couple times a year to get familiar with how the system works and if it will perform as as you expected, or if you need to adjust expectations and use for a real power outage.

For a power wall 3, it looks like there are 4,000-6,000 cycles, and that is before it goes down to only 80% of battery capacity. A cycle is all the way to zero before charging. Even if you went to zero every day, that would be nearly 11 years - and then you still have a lot of battery capacity left to use. So, I wouldn't worry about cycles

My guess is that the grid draw down from the battery that you mention earlier in this thread is only during those times of high energy usage - which is usually when the sun is baking and everyone has their AC on high. I'm pretty sure they can't draw during a power outage - and that would be spelled out in the agreement.

I'm am a long way from a guru, and don't have a built in battery back up to my solar system (a battery alone would have cost more than the system was and my state does not give incentives). As a back up system, I wouldn't worry about ROI, nor do you have to squeeze every last "saved" $$ out of your set up. You do not have to justify how/when you use any part of the system to anyone but yourself.
 
Lithium based chemistry batteries and most chemistries in general have three types of degradation. One is strictly aging. Install a battery and never use it except to maintain 40% charge. Ideally 50 Deg F steady temperature out of the sun in a well ventilated non corrosive atmosphere and it will still degrade. Anything out of the ideal range will impact lifespan "on a curve". Ideally the battery is charged and discharged at a slow and steady rate, agressive charging and discharging will also reduce long term capacity as the battery will heat up internally. My guess is the Tesla software has adjustable charge rates that keep it in an optimum range, that is easy with grid power, less easy with PV which tends to be on or off. Discharge is far more problematical, unless you are you are doing peak shifting where you charge the battery with solar during the day and then use it at night, if a grid failure occurs, you are going to want rapid discharge to keep the lights on. Lithium chemistries will respond faster and discharge deeper than other chemistries with rapid discharge but it will impact life. If you sign a deal with the power company to let them use it, they will probably use it in rapid discharge mode when the need it (within the ranges in your contract.

Note Tesla like any company will have some conservatism in their warranties. The battery will typically not fail, it will just lose capacity some capacity. On the large 3 MW Megapack I was involved with, Tesla offered a couple of options for long term battery capacity. The owner could either live with the reduced capacity or Tesla would leave empty space in the cabinet for additional batteries to be added at a later date to offset the degradation or thy would just install additional capacity to begin with but keep the nameplate rating at a lower setting. Given, the rapidly changing world of battery tech, anything you install now will be obsolete in 4 or 5 years, hopefully still functional, just replaced with bigger and better tech at a lower cost so the performance at 20 years is really not of major concern.
 
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Lithium based chemistry batteries and most chemistries in general have three types of degradation. One is strictly aging. Install a battery and never use it except to maintain 40% charge. Ideally 50 Deg F steady temperature out of the sun in a well ventilated non corrosive atmosphere and it will still degrade. Anything out of the ideal range will impact lifespan "on a curve". Ideally the battery is charged and discharged at a slow and steady rate, agressive charging and discharging will also reduce long term capacity as the battery will heat up internally. My guess is the Tesla software has adjustable charge rates that keep it in an optimum range, that is easy with grid power, less easy with PV which tends to be on or off. Discharge is far more problematical, unless you are you are doing peak shifting where you charge the battery with solar during the day and then use it at night, if a grid failure occurs, you are going to want rapid discharge to keep the lights on. Lithium chemistries will respond faster and discharge deeper than other chemistries with rapid discharge but it will impact life. If you sign a deal with the power company to let them use it, they will probably use it in rapid discharge mode when the need it (within the ranges in your contract.

Note Tesla like any company will have some conservatism in their warranties. The battery will typically not fail, it will just lose capacity some capacity. On the large 3 MW Megapack I was involved with, Tesla offered a couple of options for long term battery capacity. The owner could either live with the reduced capacity or Tesla would leave empty space in the cabinet for additional batteries to be added at a later date to offset the degradation or thy would just install additional capacity to begin with but keep the nameplate rating at a lower setting. Given, the rapidly changing world of battery tech, anything you install now will be obsolete in 4 or 5 years, hopefully still functional, just replaced with bigger and better tech at a lower cost so the performance at 20 years is really not of major concern.
PW3 is limited to max 5kw charge rate.

It’s assumed that the PW3 is Using LiFeP.

Having a battery solely for backup is definitely underutilized. Going to time of use just complicates calculations and the energy wise program. That works out to roughly $0.50/kwh if fully utilized. It’s a no brainer. With the knowledge that it will take a couple hours of sun to charge it back up the next day. Worst case scenario would be they discharge at PM peak leaving me 3 kWh in the battery and then the grid goes down and it’s cloudy the next day…. Seems rather rare. I do get to defer the draw down for a certain number of days.

The math says my system will supply 90% of my power. And I still haven’t charged much at home. So basically I could charge 800 miles a month at home for free. That’s a pretty decent deal. My free charging Tesla won’t last forever.
 
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