Tesla Powerwall 2

[gmanInPA]

Batteries make _can_ sense in a few situations, but not as many as most imagine they would. If your reasons are green (as in money or environment), fuggedaboudit.

I've outlined some of what I feel are legit reasons for batteries in this thread: https://www.solarpaneltalk.com/forum...with-batteries

One of the posts there includes a flow chart I put together to outline something of the decision-making process that one might use to consider batteries vs generator & batteries, etc.

You just had to mention to solar roof tiles, didn't you Sounds like a nice idea, but I can't imagine installation would be very easy or practical. I'd be interested to see how the circuits are wired from those tiles, etc. For me, I'd rather just have my panels separate from a good quality roof. Kinda like heat-pump hot water tanks... by consolidating, you just make it more costly when one or the other fails.

[Charlie W]

Thanks for your reply. I can get a bit wound up when talking about Tesla, and it winds up coloring my tone on other stuff. I apologize if I came across as too combative. I appreciate your input a whole lot, and will be considering it. I'll give further thought and investigation to what kind of generator. As for propane tanks, I was thinking of two 500-gallon tanks given that I have all kinds of space. Make sure to fill 'em both by the end of October. We'll see.

I'd love it if batteries made sense. I really investigated it a while back, and it didn't even remotely come close to making sense. Not anywhere even close to the ballpark in any way, shape or form. And then there are Tesla's solar roof tiles, but I shluldn't pull my string. Anyway, thanks for your ideas, honest.

[gmanInPA]

Hey charlie W... I don't disagree with your observations about Tesla. You had mentioned "Now: Grid-tie with generator, or off the grid with battery?" so I was just lending my $.02 about that remark as one who has batteries and a generator and related opinions. I use the term 'fuel extension' with batteries to mean this... if you have batteries and they power an inverter that powers your critical loads, then in a power failure, you're going to use battery power for at least some of that duration. When you generator does come on (in a hybrid setup), it typically powers the same critical loads and recharges your batteries until they reach some SoC or float, then the generator powers down and your batteries resume responsibility for powering your inverter again. So rather than your generator running for the entire duration of a grid outage, it runs a fraction of that time, thus extending your fuel supply.

In my case, my batteries give me ~14-24 hours of power for my critical loads before they reach 50% DoD. When they get to 50%, my generator kicks on and runs until the batteries are back at around 95% (this is configurable). That takes between 45 minutes and 90 minutes typically. That is about .75 to 1.5 gallons of fuel. So in a week outage with no solar, I'd be using a max of about 10.5 gallons of fuel. Fuel is cheaper than battery power typically (at present), so that isn't necessarily a fiscal advantage. However, let's say you had a 275 propane tank (only about 85-90% of which can be filled because of expansion). If you ran exclusively off a generator for 7d * 24h * 1gallong/hour that is 168 gallons of propane. That would be just fine in your case. Two weeks though and you'd be out of fuel. You mentioned trucks can't travel on some roads in your area in winter. Does that include fuel trucks?

I'm not trying to offer an opinion on whether or not to use batteries - that's entirely up to what you want to do and how much you want to run a generator. If you've got loads of propane storage and your interests are primarily in having an economical backup power source, absolutely, a generator is the way to go. I know of no setup where batteries and solar would be more economically beneficial than a generator at present, though I'm happy to learn of such if they exist!

Best wishes on your new home - sounds pretty neat.

[Charlie W]

What is fuel extention? I've never heard of that term, and have no idea what it means.

Even for time-of-use rate shifting, I see no financial value in Tesla's product. It's a lithium battery, and those things are good for 2,000 charge cycles using 80% of capacity. This would mean a Powerwall battery would store 22,000 kWh at a cost of $5,500, which works out to 25 cents/kWh. I haven't heard of any TOU market where the peak/non-peak rate differential is that wide. Not only that, but given that a typical household uses 45 kWh/day, a 14 kWh battery whose usable capacity is 11 kWh just isn't big enough. If someone bought enough batteries to time shift the whole house, they'd probably need three of them.

Over the lifetime of those batteries they wouldn't stand a chance of recouping the cost, hence my pretty firm belief that Tesla is selling a piece of smugness jewelry to match their $100K+ electric Rolexes on wheels. You can see that I'm not exactly Tesla's biggest fan. I think they are prototypical Silicon Valley hype artists who sell overpriced cars, and in the usual Silicon Valley fashion have displayed a maddening tendency to beta-test their products on the customers and then blame any subsequent defects on user error. It's this kind of thing that has put me very much on guard with ALL eco products, including solar panels.

The smugness and evangelism is thick enough to cut with a chain saw -- and it rubs this native Midwesterner the wrong way, on steroids. I'm capable of great loyalty toward companies and products, and can roll with the punches, glitch-wise. Examples would include Ram pickup trucks and Henry lever rifles. My experience with both has been out of this world. Neither of those products are cheap, but I think money spent on a Ram truck or a Henry rifle is money well spent. I think money spent on Tesla products is evidence that God made someone too rich. I'm watching carefully to see what happens to them with their Model 3. General Motors will be selling its Bolt, with range just as good and maybe a bit better than the Model 3, and regardless of what people say about GM, I would much rather buy a car from a car company than from a computer merchant.

As for SHTF stuff, well, where we're going the S does HTF pretty often, in the form of long-duration power outages. The Gorge is infamous for its ice storms, and our microclimate is snowy. (When we were land-shopping, we stood in a couple feet of snow this past March.) We'll be at 1,800 feet, and the 7 miles to the river is steep enough that large trucks are banned from the roads from first frost to last frost. Utility response time to these large scale events is described as slow, which isn't held to be a matter of incompetence but of the sheer scale of the county. So we need a generator.

It won't be powered the way you suggest. It'll run on propane, and will turn on automatically if the power goes out. It seems like a no-brainer. We will have propane tanks anyway, for the kitchen cooktop, the living room fireplace, and the supplementary furnace that kicks in when the temperatures are too low for the air-source heat pump. (I looked into a ground-source heat pump, but that's a non-starter on grounds of cost and performance; I believe I discussed it in a different post about the house I'm having built.) In any case, I wrote Generac because that's the brand I know, but you got my attention with your report of Generac failures, so I will investigate before I buy.

One other problem I foresee with a diesel generator, besides the need to have a big fuel tank in addition to the propane tank(s) that I'll have anyway, is fuel gelling. The generator is a wintertime backup. Having had my diesel truck gelling disaster (it was a beaut, as they say), I don't want to depend on diesel when the temperature is zero and we cannot get down the hill for a day or four. One last thing: I noticed you mentioned bio-diesel. So, last summer, we were out in the deep rural SE of Burns, Oregon. I filled up the Ram 3500 with B20 (20% biodiesel) and saw my fuel economy go from 16 MPG and change to 12 MPG and change. So much for eco-diesel.

10 year warranty is really low.

[gmanInPA]

Hey Guest W... sounds like a neat place to live actually... I've written about this elsewhere on this site, but batteries in your situation are going to primarily serve one purpose if you went that route - fuel extension. If you have the need for a UPS of sorts, they'd also be good for that purpose. In almost all other scenarios, a generator and grid-tie would be much more sound financially if that is your goal. You'll spend far less and probably have much more solar to harvest. If you do go with a battery/hybrid system, the key is figuring out your sweet spot between battery and generator. Many will go with a very small battery - enough for a few hours, just to give them some buffer before the generator runs. For one week a year, a battery system would not be as fiscally beneficial as a generator. If you're preparing for some sort of SHTF scenario tho... batteries will extend your fuel and would be a 'force multiplier' of sorts.

I would highly encourage you to consider a diesel generator if you plan on running it with any frequency. I have a few Generac portables, and they do alright - but there are oodles of people who have experienced failures with their Generac backup generators and during critical times. I would avoid them unless I had a very good relationship with a Generac service provider whom I totally trusted to handle any issues. Propane definitely has a fuel advantage when it comes to fuel longevity, but a solid diesel engine would last many times longer than the average Generac. Many diesels can also run on a variety of scavenged fuels like HHO, Diesel #1/2, Jet Fuel, bio-diesel, etc. That's just my opinion.

OAN: I don't think Tesla is presently building the Powerwall for those who would want to be entirely off-grid. Tesla uses the "off-grid" term with phrases like "eventually" when they do mention it. 325kWh/week is an expensive proposition for a battery-based system. Average homes are by no means economical to turn into an off-grid home (not unless we had over-unity machines, lol). Maybe if people start designing homes to be off-grid from the start, something like a Powerwall could play a part - but that doesn't appear to be their target demographic. Just look at the model homes from their unveiling. They appear to be more aimed at TOU markets and markets where people want plug-and-play alternate energy, momentary backup, and cool gadgets without necessarily understanding if they're the best value.

Oh - as far as diesel fuel gelling - totally legit concern. I live in the 'mountains' northern PA and it can get pretty cold here too. I use Pri-D to help with some of that.

[Charlie W]

I'm really glad someone else started this thread, so I can merely comment rather than start a whole new one myself.

I am building a new house in a semi-rural area in the Columbia River Gorge. The winters can be harsh, so I have been advised to plan for occasional power outages that might last as long as a week. This is in a 2,000-square mile county with 21,000 people. Not poor, but not rich, and prone to nasty ice storms and the occasional foot of snow. Self-reliance is still a necessity. Rather than rely on the sheriff, have guns. Rather than rely on the utility crew, have a generator. I've investigated solar panels, and the preliminary caluclations look promising. Now: Grid-tie with generator, or off the grid with battery?

The average house in that area uses 1,400 kWh/month according to the local utility. Which is 325 kWh a week. Tesla's new Power Wall stores 14 kWh. As the owner of an electric car (long story), I know that lithium batteries hate to be drawn down below 20% state of charge. Yep, you can do it, but do it very often and you KILL the battery life. So that 14 kWh should be called 11.5 kWh of usable capacity. To run the house for a week, we'd need 25 batteries. At $5.500 a pop, that's $137,500.

Sorry, Elon Musk, but I think I'll go get myself a Generac. I'm going to have a big ol' propane tank or two anyway, to run the backup furnace, the kitchen range, the water heater, and the fireplace. $10K vs. $137.5K? May I suggest that you concentrate on making sales to rich, stupid, smug California eco-yuppies, not to put too fine a point on it? You're welcome. By the way, your new Model X goes for $140K, and I understand that them gull-wing doors don't work so well. I got my EV for $8,500 after the tax credit. My mother didn't raise a California fool.

[gmanInPA]

What I find funny is that they want a $500 deposit per powerwall without describing anything about how it would work with an existing system. Sure - let me just hand you some money for your vaporware so you have some additional working capital. Also funny is how they estimate it based on number of bedrooms - you know - because bedrooms are such heavy users of power in most homes

[PNjunction]

Right now, vaporware for the average consumer, despite the recent introduction on a film set.

To me, the Tesla products are the Duesenberg's of the past, when what was demonstrated by Henry Ford was that if you want to revolutionize the world (in his case forcing the change from limited electric to fossil fuel), the Model-T for the average consumer is what is needed for the revolution from Tesla.

I must give him credit to his namesake though - the remote-controlled boat wasn't so far fetched now that we have autonomous S-models.

[Sunking]

That is some funny stuff. I don;t care who you are. AH mean nothing. Absolutely nothing.

[inetdog]

Getting better, but that's still only about 300AH

AH is not a particularly appropriate measure for storage capacity of a battery bank if the system voltage is not specified. Useful for comparison only if the nominal voltage of PowerWall 1 and 2 are the same.

[RedDenver]

Quick back of the envelope lifetime costs, assuming that the battery lasts exactly the warranty length (10 years) and that the $5500 is the price to consumers:

5500/(365.25*10) = $1.50/day

Assuming 25% DoD average over life of the battery (3.5 kWh/day): 5500/(365.25*10)/3.5 = $0.43/kWh
50% DoD average (7 kWh/day): 5500/(365.25*10)/7 = $0.215/kWh
75% DoD average (10.5 kWh/day): 5500/(365.25*10)/10.5 = $0.143/kWh

[Logan5]

Getting better, but that's still only about 300AH

[extrafu]

Hi folks,

2 days ago, Tesla announced the Powerwall 2. The specs are pretty nice: 14 KWh, integrated inverter, 10 years warranty - for 5,500 US$.

I know that message thread will get heated, but what is opinion on that thing?

Thanks!