The Tesla Powerwall is an inverter and battery storage all in one. You can use it with or without solar panels. without panels just think of it as a whole home battery backup with the brains to automatically switch on and off when needed. The grid charges the batteries, and the batteries are ready to be used when needed. You can also use them to take advantage of different electricity plans, for example, if you had a plan that was free electricity at night, you would use the grid at night and the Powerwall during the day as long as it would last, and then at night while you are using the free electricity it would also charge the batteries for free. That's an extreme example, but there are plans with different rates depending on demand and the Powerwall has the brains to automatically find all that stuff and optimize your grid usage to reduce your bill while also serving as an emergency backup. Obviously using it with solar panels is the best bang for your buck, but Tesla's AI brains and Apps and all that stuff is where they lead. Combining the inverter and batteries into one package, and combine that with their Apps, it makes it extremely easy for the installers.
Residential Solar Power Systems
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Last: 18 hrs ago by h_town_ags
The industry seems like it has gravitated to 30 years as being the expected lifetime. They have all the literature you could ever want to try and hammer that point home, but who knows?MRB10 said:
-What are they telling you about the useful life of the equipment?
-What literature did they provide to prove their number?
-How long do they warranty the panels and batteries?
-When should you reasonably expect output to start being reduced due to age or normal wear of the equipment ?
My installer has a 25 year product, labor, and performance warranty (signed contract). But installers go out of business so I default to the manufacturer of the components. I'm using REC panels, they have a 20 year product warranty and a 25 year linear performance warranty. The linear performance warranty just means that the expected degradation will be linear through the entire 25 years. In my case with the REC panels, the warranty states a .25% annual degradation is allowable (each panel is individually monitored) and at the end of 25 years I should still be producing 92% power. I'm using Pytes batteries, they have a 6000 cycle warranty that states it will be above 90% depth of discharge (when installed by a certified installer). I'm planning to be using my batteries at night so a nightly discharge is expected, that's about 15 years. The inverters have a 10 year warranty, this would be the only one where I really hope my installer is still around for their 25 year warranty. I'm getting two inverters and they are $7500 each.
Batteries are currently expensive, I'm hoping that by the end of the warranty battery technology has jumped enough that to get a direct replacement won't be too expensive
someone once made this comment about solar and its stuck with me.....if it was worth it every company that owns a building would have panels on every square inch.
If you look at it strictly from a financial perspective, it isn't worth it in most cases for a business. They already have business interruption insurance that will cover them if the power goes out and they have to send everybody home for a week. But how much is it worth to not spend a week in August sweating your balls off after a hurricane knocks out all the power to your area? How much is it worth to not spend a week freezing your ass off in February after an ice storm knocks out the power? How much is it worth to not have a freezer full of wild game you paid good money to hunt go bad because you can't get enough gas for your generator to keep it running or the natural gas supply gets cut off/slowed down by a power outage and your generator won't run?ought1ag said:
someone once made this comment about solar and its stuck with me.....if it was worth it every company that owns a building would have panels on every square inch.
Those unlikely scenarios have all happened in Texas for thousands of people within the last 5 years. What is the value of having the peace of mind to be able to withstand those kinds of things without having to scramble for gas, ice, get propane delivered, etc.? When you add that value on top of the lack of an electric bill, for some people it makes sense.
I am in the large-scale (1000+ acres) solar business. I would not do rooftop solar, but I will be very interested in a system like OP's when I finally find some land to buy. Ground mounted systems > rooftop.
Well, I own a business and that business owns the building, and while I think it makes sense for my residence, when you start talking about commercial, the motivation starts to wain. First of all, the scale of economies is vastly different. The percentage of our operating budget spent on the companies electricity usage is so small, it doesn't even register in the reports. For one, people are only there for 8-10 hours a day, 5 days a week, and no weekend usage. Another issue, we only occupy about 1/3 of the building, the other areas are leased out with NNN leases. When you start trying to bring tenants along on the ride it can get a little hairy, especially when talking about roof penetrations, and the liability associated if something happens.
Not to mention, if you've looked at commercial prices on anything, there is a big difference between residential and commercial. And as another poster stated, while backup power is a big motivator for me on the residential side, I have no need (or very little) for backup power for my business, my business is right across the street from a major hospital and the grid power has always been a priority.
My guess is companies that are high energy users, like crypto miners, are probably doing it. And for better or worse, when I look at ROI for my company, I have much higher expectations with shorter break even timeframes.
Not to mention, if you've looked at commercial prices on anything, there is a big difference between residential and commercial. And as another poster stated, while backup power is a big motivator for me on the residential side, I have no need (or very little) for backup power for my business, my business is right across the street from a major hospital and the grid power has always been a priority.
My guess is companies that are high energy users, like crypto miners, are probably doing it. And for better or worse, when I look at ROI for my company, I have much higher expectations with shorter break even timeframes.
Lots of good info in this thread. I'll add some of what I have learned about solar over the last 20ish years as a consultant and engineer on high performance homes and commercial buildings. There's so much bad information out there with regard to solar and if it makes sense for you. OP, I'm glad to see you've done your homework and you're not getting taken advantage of by one of these solar lease companies or whatever. There's some really shady (pun intended) companies selling solar these days. Couple of points:
Best case scenario - you're building or already own a high performance house, design in or anticipate adding solar/batteries/generator at a later date, have a ground mount option, and have an electric provider that gives you good incentives or a good credit for power going back on the grid.
Worst case scenario - you have an average or below average performance home, no previous plan or prep to install solar, no ground mount option, poor roof orientation or shading, and not a good situation with the electric provider.
- Weather a solar system makes sense for you COMPLETELY depends on the location due to what your electricity provider credits you when you put power back on the grid. I have a 4K PV system on our house in CO and we are fortunate to be in place where the power provider gives us 1:1 credit, which is very rare. There are no laws that require power providers to do anything with regard to net metering, incentives, etc that I am aware of. That is the absolute first thing you have to look at when doing the financial analysis of weather or not a solar system makes sense for you and a lot of these companies that are selling solar as a financial solution (reduce your electric bill by more than the monthly payment) are not doing that.
- You have to consider how long you are going to be in the house where you're thinking about installing solar, obviously. Don't expect to get any additional value on an appraisal if/when you do decide to sell. This has been an issue since residential PV systems started getting popular. Most people will not stay in a house long enough to substantially benefit from installing a system and appraisers don't know how to asses and add value when they see a solar system on the roof. The system we have in CO was on the house when we bought it and the appraiser didn't even mention the system in the report.
- Ground mount is far better than roof mount. Solar panels get dirty, covered in snow/ice, etc and need to be cleaned to perform well.
- PV and batteries are not a good off grid/power failure solution alone for most homes, in my opinion. As discussed, we do have inverters now that will allow you to use battery and solar power when the grid fails but battery storage is still pretty expensive when you look at $/kWh. I haven't looked at Tesla walls in a while but they use to only be 13 kWh which isn't enough power to run a typical HVAC system for very long. Probably wouldn't even make it through a night if you're dealing with a power loss after a hurricane or major winter storm. Not saying it isn't possible but there are a lot more cost effective ways to accomplish long term power back up or off grid capability using a combination of only solar and battery power. We also have a generac whole house generator and its an absolute life saver when we lose power during a big snow storm. I intend to couple mine with my solar system and battery storage - have all the components just need to put it all together. If you're mostly concerned about long term power failure, get a whole house generator first. Even better if its powered by your own propane supply. That's about as reliable as it gets. If you do want to rely on batteries and solar only, most people will isolate critical loads (freezer/refrigerator, select outlets, etc.) but rarely include the HVAC system because it is so power hungry.
- Orientation of panels use to be absolutely critical for good performance but that's not as important with new panel technology. I still wouldn't install panels on a north slope but others may disagree. More reason to go ground mount is you can set the panels up at the optimum angle and some even adjust during the year as the sun moves.
- The life and long term production from panels is still somewhat of a grey area - in a good way. Our panels are almost 15 years old and they still produce pretty close to what they were designed to do even in the harsh high altitude sun where you would expect them to degrade faster. I think its completely reasonable to expect panels to produce at or damn near their original output well into 20-25 years.
- Off grid living using only solar and battery power is a different mindset. I have one client that has successfully accomplished this but everything was built with this in mind. They are ok knowing that electricity is a very limited resource and may have to deal with some discomfort due to that. I have another client that was completely pissed off when they lost power during the winter storm and the batteries (two Tesla walls) ran out of power in a matter of a few hours - because they continued to operate as if nothing changed. Really poor client education before I got involved on that one.
Best case scenario - you're building or already own a high performance house, design in or anticipate adding solar/batteries/generator at a later date, have a ground mount option, and have an electric provider that gives you good incentives or a good credit for power going back on the grid.
Worst case scenario - you have an average or below average performance home, no previous plan or prep to install solar, no ground mount option, poor roof orientation or shading, and not a good situation with the electric provider.
You don't need solar for those problems. You need a massive battery backup.
Shane '91
If the roof is being replaced as part of a covered storm (hail) claim, then the d&r is covered.EMY92 said:
My big fear with solar is needed to get a new roof after the panels are in place. It's not cheap to have a contractor remove then reinstall the panels. My guess is that the cost of that alone would exceed any savings that you expect.
Good info, thanks. The payoff math still doesn't make sense for my situation and my $1,700 portable Nat gas generator is good enough in a pinch that I have little incentive to try and justify solar.
My assumption was that useful life was closer to 10-15 years but it sounds like that belief is outdated.
My assumption was that useful life was closer to 10-15 years but it sounds like that belief is outdated.
If you can sell excess lower back at the retail rate why pay for storage. Your payback has to be better by doing solar only and scrapping the batteries and getting a gas gen backup. You can use a portable gas generator for a fraction of the cost of batteries.
The case for batteries is really for locations without net metering to offset more costs. For you, there is no additional costs savings of using batteries.
The case for batteries is really for locations without net metering to offset more costs. For you, there is no additional costs savings of using batteries.
You can't really financially justify the batteries if you're getting 1:1 from your power provider. The grid is essentially your battery. I'm just doing it because I want to and its a bit of redundancy for power back-up.
The technology that is in the Tesla wall system is pretty awesome, especially if you're in a location that has sliding rates like California. Its smart enough to know when power is cheap and to pull fro the grid for the house and to recharge. I expect we will start seeing more variable rate structures in the residential market but I also use to push solar panels and energy saving measures expecting we would be paying $0.25/kWh by now.
The technology that is in the Tesla wall system is pretty awesome, especially if you're in a location that has sliding rates like California. Its smart enough to know when power is cheap and to pull fro the grid for the house and to recharge. I expect we will start seeing more variable rate structures in the residential market but I also use to push solar panels and energy saving measures expecting we would be paying $0.25/kWh by now.
There are relatively few places that are buying back power at the retail rate. Most are buying back at the wholesale rate, which is generally fairly low in the middle of the day when solar generation is at its peak. The case for batteries is not made just by savings on electric bills using battery power overnight, it is made by not having to have a generator to cover minor outages and having sustainable power for longer outages.h_town_ags said:
If you can sell excess lower back at the retail rate why pay for storage. Your payback has to be better by doing solar only and scrapping the batteries and getting a gas gen backup. You can use a portable gas generator for a fraction of the cost of batteries.
The case for batteries is really for locations without net metering to offset more costs. For you, there is no additional costs savings of using batteries.
txags92 said:There are relatively few places that are buying back power at the retail rate. Most are buying back at the wholesale rate, which is generally fairly low in the middle of the day when solar generation is at its peak. The case for batteries is not made just by savings on electric bills using battery power overnight, it is made by not having to have a generator to cover minor outages and having sustainable power for longer outages.h_town_ags said:
If you can sell excess lower back at the retail rate why pay for storage. Your payback has to be better by doing solar only and scrapping the batteries and getting a gas gen backup. You can use a portable gas generator for a fraction of the cost of batteries.
The case for batteries is really for locations without net metering to offset more costs. For you, there is no additional costs savings of using batteries.
You are missing my point or mistaking my questions/comments to OP as general question about solar.
The point is he lives in a unique are of Texas where he actually gets full retail rate net metering. Battery storage adds zero value to the FINANCIAL proposition of resi Solar which was what he was asking about.
If he wants backup generation I would go with a generac gas unit. Basically the same cost as a powerball and doesn't have to be replaced 2-3 times over the life of the panels. It will also run for as long as it's needed vs batteries which can only last so long (and building up excess supply only hurts ROI)
Unless he is buying from SunRun (which isn't a great credit) the solar company he is buying from is not going to be around for 25 years. Generac is a much safer bet in that regard.
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