Should I add a power wall now or can I get one later?

[Epradox]

So I am nearing the completion of all the documents and permitting to get started on my solar install. I am wondering if I should ask to add a power wall now or wait til power wall v3 comes out to add it?

currently my system size is going to be 17.425kW in Florida and will be net metering back to duke energy for any excess production. My thought process was to utilize the net metering to offset my nightly consumption and add a power wall later when the new versions come out. They are currently installing 2x 7.6kw inverters on the outside of my house and I was planning on installing a power wall inside the garage. Would it be the same high installation cost after the fact if inverters are already there and permitted?

 

[jjrandorin]

Would it be the same high installation cost after the fact if inverters are already there and permitted?

Yes, it will be the same (or higher) installation cost to install it later vs now. Most likely higher installation cost than now, actually. Thats also way too much solar for 1 powerwall, so adding (1) now would require a re work of the plan they are doing since you would have to have a critical loads panel, and non backed up loads panel.

You can always "get it later" just like you can for any other construction project. In this case, this is like re doing your kitchen now, then asking if you can buy a 48inch range and get it installed later, when your current spot for your range is only 30 inches.

 

[wwu123]

So I am nearing the completion of all the documents and permitting to get started on my solar install. I am wondering if I should ask to add a power wall now or wait til power wall v3 comes out to add it?

currently my system size is going to be 17.425kW in Florida and will be net metering back to duke energy for any excess production. My thought process was to utilize the net metering to offset my nightly consumption and add a power wall later when the new versions come out. They are currently installing 2x 7.6kw inverters on the outside of my house and I was planning on installing a power wall inside the garage. Would it be the same high installation cost after the fact if inverters are already there and permitted?

It will certainly be a much higher installation cost if done separately. First, no one charges as low as Tesla for installing Powerwalls, but you can only get that low install price at the time you get solar installed as they currently don't do Powerwall-only install projects. They have hinted on the website about selling Powerwall equipment a la carte, i.e. BYO installer, but pretty much no one here has found a contractor that will charge as little as Tesla does (again in a bundled solar project).

Secondly, Powerwall installs need more than just your solar inverters, there are wiring and layout considerations regarding your solar, your main panel, and the gateway needed for Powerwall. If you don't have these things considered in your solar design, it'll again be even more costly later, as they may have to do significant re-work or retrofitting of your solar inverters and main panel. That in turn could void your warranty on you solar install, if that has to be touched.

 

[Epradox]

Yes, it will be the same (or higher) installation cost to install it later vs now. Most likely higher installation cost than now, actually. Thats also way too much solar for 1 powerwall, so adding (1) now would require a re work of the plan they are doing since you would have to have a critical loads panel, and non backed up loads panel.

You can always "get it later" just like you can for any other construction project. In this case, this is like re doing your kitchen now, then asking if you can buy a 48inch range and get it installed later, when your current spot for your range is only 30 inches.

Too much solar for one powerwall meaning I would be required to add multiple or can I get away with one and net meter the rest back into the grid? If I get one installed can I mix and match v2s and v3s later on? Just wondering how I should do this to prep for future powerwall expansion.

It will certainly be a much higher installation cost if done separately. First, no one charges as low as Tesla for installing Powerwalls, but you can only get that low install price at the time you get solar installed as they currently don't do Powerwall-only install projects. They have hinted on the website about selling Powerwall equipment a la carte, i.e. BYO installer, but pretty much no one here has found a contractor that will charge as little as Tesla does (again in a bundled solar project).

Secondly, Powerwall installs need more than just your solar inverters, there are wiring and layout considerations regarding your solar, your main panel, and the gateway needed for Powerwall. If you don't have these things considered in your solar design, it'll again be even more costly later, as they may have to do significant re-work or retrofitting of your solar inverters and main panel. That in turn could void your warranty on you solar install, if that has to be touched.

Alright sounds like the general consensus is to do it with the solar panels so I will talk to my advisor to see if it can be reworked. I’m sure it’ll be a pita to redesign but better now than later I guess.

 

[jjrandorin]

Too much solar for one powerwall meaning I would be required to add multiple

This (or you will likely need a big rework of your currently planned solar install to have a critical loads only panel and a non backed up loads panel).

 

[Matt-FL]

My suggestion is to do it all now, as it will almost never be cheaper in the future - plus the benefits can be significant.

Duke does not provide 1:1 net metering, in fact it looks like 1/3 (2022 NEM rates were 6.631c/kWh - 2021 NEM rates were 1.986c/kWh). That means for every 20 kWh you use at night, you'll need to push back excess ~60kWh during the day. If your goal is bill zero, you will be hard pressed to do it by solar alone. With 17kW system, I'm guessing you'll average 100-120kWh on a full sun day. That equates to more than half going back to the grid to get net zero.

In addition, if your area loses power, even though you have solar, your production is shut down also - unless you have batteries. This shutdown is required by your power company to keep excess produced electricity from outputting to the grid and into the line workers. If you have batteries, your system can isolate and continue working, albeit if your batteries are at 100%, grid is down, your solar will shut down and run off batteries. The excess electricity needs somewhere to go, so it turns off solar until the batteries deplete to a certain level before switching solar back on.

One powerwall would be possibly enough to run your lights, TV, computer, refrigerator, maybe a window air conditioner. It will not run your water heater, central AC and other major appliances. This will mean a subpanel with backup loads and some rework of your main panel. Instead of putting a few thousand into this rework, might be better to get another battery or two and use your main panel as the backup load center. In the event of an extended outage, you still have the capability to shut down excessive loads as needed. But, if you went with a subpanel backup load center, you can't move a main panel circuit to your backup panel after the fact - at least not easily.

I'm in the same boat - 1:3 net metering in Florida (JEA). I went with a 20.4kw system + 4 PWs. My grid usage since PTO has been consistently in the negative overall, but even with 4 powerwalls I still have times where my batteries deplete on consecutive cloudy days. I went with as much as my roof could handle and I could comfortably afford, and presently sitting at about 123% solar offset. 10.5 months in, and I've calculated a $4,507 savings - beyond what my conservative estimates were. I'm 1.5 months ahead of schedule .

Let me add this - I'm in a house full of teenage kids, washer and dryer may as well be commercial and my wife decided that now we have 'free' power, the AC is set far lower than it used to be (after 25 years of marriage, I know which battles to fight and which battles I am guaranteed to lose - this is definitely the latter). Not to mention my hot water heater may as well have a 'stuck on' switch - but I went with a heat pump hybrid and solved that by putting it in heat pump only mode, dropped from 5kw to 500w, but it does run ~ twice as long. Still far less than elements only.

hth

 

[jjrandorin]

Let me add this - I'm in a house full of teenage kids, washer and dryer may as well be commercial and my wife decided that now we have 'free' power, the AC is set far lower than it used to be (after 25 years of marriage, I know which battles to fight and which battles I am guaranteed to lose - this is definitely the latter). Not to mention my hot water heater may as well have a 'stuck on' switch - but I went with a heat pump hybrid and solved that by putting it in heat pump only mode, dropped from 5kw to 500w, but it does run ~ twice as long. Still far less than elements only.

This is pretty much always the case if someone has a significant other in the picture (gender really doesnt matter here), once someone gets solar. They watch all the planning, construction, justification for spend, etc, then once everything is done, home power usage almost always goes UP, and almost never down.

Even if someone had the household conditioned toward conservation (turning all lights off when exiting room, etc), no one wants to hear that anymore and the response is " But, we got solar now, right? Why do we still have to do any of that?"

Thats another reason why, when asked, I always say get as much solar as your roof will hold, or as much as you can, NOT what you currently think you need.

 

[h2ofun]

This is pretty much always the case if someone has a significant other in the picture (gender really doesnt matter here), once someone gets solar. They watch all the planning, construction, justification for spend, etc, then once everything is done, home power usage almost always goes UP, and almost never down.

Even if someone had the household conditioned toward conservation (turning all lights off when exiting room, etc), no one wants to hear that anymore and the response is " But, we got solar now, right? Why do we still have to do any of that?"

Thats another reason why, when asked, I always say get as much solar as your roof will hold, or as much as you can, NOT what you currently think you need.

Yep, I went nuts getting the 30kw. But I have NO regrets. The wife is totally happy because we can heat and warm our large house to whatever we want. She can do laundry whenever. I can now have a EV car, and charge other friends EV's for free. I have yet to ever use my 7 powerwalls, so I tell 100% of folks who ask they are a waste of money, unless you have money to burn. BUT, get as much solar as you can!!

 

[hmcgregoraz]

We started with 18.5KW DC / 20KW Inverter as that was basically all we could get thru the local utility approvals, since it was estimated at 124% of our prior year usage, which was low due to covid (not driving much, Model X and 3 at the time, Model X, 3, and Y now). We financed via Clean Energy Credit Union, and it went well.

We then expanded to ~23.5KW DC / 20KW inverter with our local installer, it would have been cheaper to do it all at once, but that was not an option for us. We pulled this into a re-fi of the solar loan through a local credit union, TopCU, at an lower interest rate due to timing.

We also planned for the 3x powerwalls at the time of the expansion, but the timeline for delivery meant a later install, and two invoices, etc. We then re-fi again via TopCU, but at a higher interest rate due to timing. We accepted the higher interest rate vs paying cash on the power walls due to trying to keep everything related to the house under my mom for a variety of reasons.

Our net metering is paying us back at $0.086/KWh, and we pay between $0.11 and $0.15/KWh that we draw from the grid. The powerwalls have helped a ton, but do not fully offset their cost. Just yesterday we had two ~10 minute power outages during a summer storm, and only noticed that the lights got slightly brighter during the switch to off grid.

It would have probably shaved about 10% off the total if we could have done it all in one shot. That being said we tried to be ready for the next step on each step to make sure we could get there.

-Harry

 

[Epradox]

This (or you will likely need a big rework of your currently planned solar install to have a critical loads only panel and a non backed up loads panel).

I see but with no powerwalls, its fine? I am a little confused on how you're envisioning the setup. Theres 3 sub panels, 2 for the house and 1 for the pool. The biggest draws in the house are the AC units and pool pump. I believe one ac is on one panel and the other is on the 2nd panel with the pool panel controlling the heater/pump. Are you saying if a single powerwall was installed it would have to be wired to disconnect one of the panels? Would I just be better off without a powerwall then if it wont complicate the install?

My suggestion is to do it all now, as it will almost never be cheaper in the future - plus the benefits can be significant.

Duke does not provide 1:1 net metering, in fact it looks like 1/3 (2022 NEM rates were 6.631c/kWh - 2021 NEM rates were 1.986c/kWh). That means for every 20 kWh you use at night, you'll need to push back excess ~60kWh during the day. If your goal is bill zero, you will be hard pressed to do it by solar alone. With 17kW system, I'm guessing you'll average 100-120kWh on a full sun day. That equates to more than half going back to the grid to get net zero.

In addition, if your area loses power, even though you have solar, your production is shut down also - unless you have batteries. This shutdown is required by your power company to keep excess produced electricity from outputting to the grid and into the line workers. If you have batteries, your system can isolate and continue working, albeit if your batteries are at 100%, grid is down, your solar will shut down and run off batteries. The excess electricity needs somewhere to go, so it turns off solar until the batteries deplete to a certain level before switching solar back on.

One powerwall would be possibly enough to run your lights, TV, computer, refrigerator, maybe a window air conditioner. It will not run your water heater, central AC and other major appliances. This will mean a subpanel with backup loads and some rework of your main panel. Instead of putting a few thousand into this rework, might be better to get another battery or two and use your main panel as the backup load center. In the event of an extended outage, you still have the capability to shut down excessive loads as needed. But, if you went with a subpanel backup load center, you can't move a main panel circuit to your backup panel after the fact - at least not easily.

I'm in the same boat - 1:3 net metering in Florida (JEA). I went with a 20.4kw system + 4 PWs. My grid usage since PTO has been consistently in the negative overall, but even with 4 powerwalls I still have times where my batteries deplete on consecutive cloudy days. I went with as much as my roof could handle and I could comfortably afford, and presently sitting at about 123% solar offset. 10.5 months in, and I've calculated a $4,507 savings - beyond what my conservative estimates were. I'm 1.5 months ahead of schedule .

Let me add this - I'm in a house full of teenage kids, washer and dryer may as well be commercial and my wife decided that now we have 'free' power, the AC is set far lower than it used to be (after 25 years of marriage, I know which battles to fight and which battles I am guaranteed to lose - this is definitely the latter). Not to mention my hot water heater may as well have a 'stuck on' switch - but I went with a heat pump hybrid and solved that by putting it in heat pump only mode, dropped from 5kw to 500w, but it does run ~ twice as long. Still far less than elements only.

hth

I am being told that they are offering me 1:1 net metering with my call with Tesla. I will have to reread the contract with Duke to verify this. This is primarily the only reason I am debating getting powerwalls at all. If I can export at 1:1 back to the grid during the day, then at night I can just use the excess from my account.

It does seem like my consumption will eat through a single powerwall quite quickly so now I am debating on a second route and seeing if it make sense to wire in an automatic backup generator. I imagine this wouldnt be overly difficult? Also the pricing of multiple powerwalls is getting close to the pricing of an f150 lightning with intelligent backup power.. hmm..

 

[hmcgregoraz]

There are two methods to deploy powerwalls, and a bit of a hybrid option too.

Whole House Backup, the powerwall gateway or backup switch goes in line with your current main panel, all loads get backup power. Depending on your loads, you may need three or more powerwalls for this to work, especially in a heavy Air Conditioning usage area. The powerwall gateway acts as an automatic transfer switch, to cut off the grid connection during an outage. Essentially all loads are considered critical loads in this type of install.

Critical loads backup, the powerwall gateway essentially goes in parallel with your current main panel, and your "critical" loads are moved to gateway itself, or a sub panel off the gateway, it still cuts off the grid during an outage, but it also cuts off anything not on the critical loads. With. multiple panels existing, and trying to figure out what loads are "critical" and not too much current draw, you would have a fair amount of re-wiring to be able to install as single powerwall and select the loads you wanted.

To further complicate things, the powerwall gateway only really works with an up to 200 amp service, it does not work with a "split 400", which really is kinda two 200 amp services in one meter main. We had moved to a 400 amp service from a 60 amp service during our major remodel, as the cost diff vs 200 amp with our utility at the time was virtually zero.

We technically have critical loads setup, using one of our two 200 amp mains off our split 400 service. We have the future pool equipment and a tesla wall connector on the other 200 amp side of our 400 amp service, and they are "not critical loads", but we have the primary 200 amp going thru the tesla gateway, which provides power to a sub in our garage (which used to be one 200 amp itself), and a sub in our storage closet (which used to be on the other 200 amp), as well as a sub dedicated to 6 of our 9 mini split AC units. The amount of re-wiring was not zero, but was not insane, and we were able to get all of our mini split AC units on the critical loads side. If we had only gone with 2 powerwalls, we would not have had enough current or storage to do this, and would have only been able to easily backup the panel in the garage, which would have covered 3 of our mini splits, and if we had other critical loads it would have been a ton of re-wiring to get them serviced by the garage panel.

If you are looking at a backup generator, I would consider pricing 3 or 4 powerwalls vs the backup generator and ATS. I suspect the costs will be similar after tax credits. You could most likely leave your pool panel off the critical loads if necessary depending on how the panels are wired.

Also, I would look at Powerwall+ as it basically bundles a 7.6KW inverter, ie two Powerwall+ plus two powerwall 2.

-Harry

 

[Epradox]

There are two methods to deploy powerwalls, and a bit of a hybrid option too.

Whole House Backup, the powerwall gateway or backup switch goes in line with your current main panel, all loads get backup power. Depending on your loads, you may need three or more powerwalls for this to work, especially in a heavy Air Conditioning usage area. The powerwall gateway acts as an automatic transfer switch, to cut off the grid connection during an outage. Essentially all loads are considered critical loads in this type of install.

Critical loads backup, the powerwall gateway essentially goes in parallel with your current main panel, and your "critical" loads are moved to gateway itself, or a sub panel off the gateway, it still cuts off the grid during an outage, but it also cuts off anything not on the critical loads. With. multiple panels existing, and trying to figure out what loads are "critical" and not too much current draw, you would have a fair amount of re-wiring to be able to install as single powerwall and select the loads you wanted.

To further complicate things, the powerwall gateway only really works with an up to 200 amp service, it does not work with a "split 400", which really is kinda two 200 amp services in one meter main. We had moved to a 400 amp service from a 60 amp service during our major remodel, as the cost diff vs 200 amp with our utility at the time was virtually zero.

We technically have critical loads setup, using one of our two 200 amp mains off our split 400 service. We have the future pool equipment and a tesla wall connector on the other 200 amp side of our 400 amp service, and they are "not critical loads", but we have the primary 200 amp going thru the tesla gateway, which provides power to a sub in our garage (which used to be one 200 amp itself), and a sub in our storage closet (which used to be on the other 200 amp), as well as a sub dedicated to 6 of our 9 mini split AC units. The amount of re-wiring was not zero, but was not insane, and we were able to get all of our mini split AC units on the critical loads side. If we had only gone with 2 powerwalls, we would not have had enough current or storage to do this, and would have only been able to easily backup the panel in the garage, which would have covered 3 of our mini splits, and if we had other critical loads it would have been a ton of re-wiring to get them serviced by the garage panel.

If you are looking at a backup generator, I would consider pricing 3 or 4 powerwalls vs the backup generator and ATS. I suspect the costs will be similar after tax credits. You could most likely leave your pool panel off the critical loads if necessary depending on how the panels are wired.

Also, I would look at Powerwall+ as it basically bundles a 7.6KW inverter, ie two Powerwall+ plus two powerwall 2.

-Harry

Thank you Harry this is very informative. Sounds like I’ll need to have quite a few powerwalls for whole home backup but I do believe one of my panels has most of the critical items on it(main ac and kitchen). So I guess I could get away with 1 on that panel? How many powerwalls did you end up installing?

It looks like tesla is recommending me 3 powerwalls if I want whole home backup. This effectively doubles my install cost though still cheaper than most companies charging for solar panels only of the same size. The only thing I’m concerned about is my need for it and it’s livelihood. If I need to replace these every 10 yrs or so, that’s an annoying cost. If the new powerwalls come with a high lifecycle long life battery chemistry, I’ll be pretty pissed I spent the money on this iteration.

So basically I think my biggest concern for now is not even battery back up as I don’t actually really care about that at the moment. I am more concerned about how much of a hassle is it to include a gateway later vs now. Is it pretty much the same as adding an ATS at the meter?

Also can the panels be used with another battery system or does it need the gateway in order to redirect the flow of energy?

 

[Epradox]

Duke does not provide 1:1 net metering, in fact it looks like 1/3 (2022 NEM rates were 6.631c/kWh - 2021 NEM rates were 1.986c/kWh). That means for every 20 kWh you use at night, you'll need to push back excess ~60kWh during the day. If your goal is bill zero, you will be hard pressed to do it by solar alone. With 17kW system, I'm guessing you'll average 100-120kWh on a full sun day. That equates to more than half going back to the grid to get net zero.

So after doing a little digging I believe those rates that you have published are for excess credits that have not been used after 1 calendar year.

“In the unlikely event that a customer has unused energy credits after a full calendar year, DEF will cash out the energy credits at a wholesale rate, as opposed to the retail rate on the customer’s monthly bill.”

So from that it sounds like it is is 1:1 retail metering and any unused excess after a year gets paid out at 1:3. Hopefully I’m reading that right.

 

[Matt-FL]

You are correct, I went straight to the table. I don't see anywhere that claims 1:1, but don't see anything contradicting that either. That's really rare now in Florida, especially with the FPSC rules. Glad you are able to get that! My utility is not part of FPSC, so they get to write their own rules.

 

[hmcgregoraz]

Thank you Harry this is very informative. Sounds like I’ll need to have quite a few powerwalls for whole home backup but I do believe one of my panels has most of the critical items on it(main ac and kitchen). So I guess I could get away with 1 on that panel? How many powerwalls did you end up installing?

It looks like tesla is recommending me 3 powerwalls if I want whole home backup. This effectively doubles my install cost though still cheaper than most companies charging for solar panels only of the same size. The only thing I’m concerned about is my need for it and it’s livelihood. If I need to replace these every 10 yrs or so, that’s an annoying cost. If the new powerwalls come with a high lifecycle long life battery chemistry, I’ll be pretty pissed I spent the money on this iteration.

So basically I think my biggest concern for now is not even battery back up as I don’t actually really care about that at the moment. I am more concerned about how much of a hassle is it to include a gateway later vs now. Is it pretty much the same as adding an ATS at the meter?

Also can the panels be used with another battery system or does it need the gateway in order to redirect the flow of energy?

As far as can Tesla solar be used with a diff battery system, as long as it is an AC interconnect battery system, and has it's own "gateway" of sorts, it really would not matter the solar vs battery vendor. That being said, Tesla PowerWalls are still the cleanest and safest battery solution in the US market.

We went with 3x PowerWalls, and are running about 80-95% self powered, depending on how much we need to charge the cars and how quickly.

This was yesterday, with relatively little car charging, and reserving 30% capacity for backup power.

Yes, different battery chemistries may have differnt life spans, but the 10 year powerwall warranty was "enough" for us, and the changes in 5 or 10 years should let us retro fit the system with more capacity for less $ then.

As I stated in another thread, if it's just a $ against net metering (Even very lop sided net metering, which it appears you do not have), it generally does not pencil out. If you compare $ wise vs an ATS and a generator large enough to run the loads you want to run, and fuel storage, it becomes an easier balance. Natural Gas generators are not exactly the best choice for weather related issues, as a lot of times when electrical issues hit, so do natural gas supply issues. LP tank/storage/delivery needs to be factored in, or ugh, Diesel.

Here is the last 7 days of data, we had a couple of larger driving days across several of the teslas, and due to our summer storm season starting I opted to just charge from the grid a bit more.

I generally like to add to what ever the installer/vendor is suggesting when it comes to solar, power walls seem to be better at sizing, and I suspect Teslas suggestion of 3 is probably reasonable.

For solar I always suggest adding at least 2 panels over what the vendor is suggesting, sometimes as much as 10-20% over their suggestion.

Panels are relatively cheap at original install, and expensive as an addon, if it is even possible (tesla does not do add ons, they do additional small systems with inverter, etc).

-Harry