Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Powerwall 2 and Integrated Solar

powerwall.tesla.com

Post reply on HN
Print view View original

131–140 of 341 posts

Re: Powerwall 2 and Integrated Solar

#131

Post by ascorbic »

Loic wrote: post #118

Quick question for the people living in the US (Target customers of the Powerwall). What is your yearly power usage? On the website[0] they put for sizing 10kWh/day/BR. Which means 14600kWh/year for a 4 bedroom house. Here in Germany, working from home with a 4BR+office house, we are using 2550kWh/year. So, I suppose the Tesla sizing is to support a "peak day" usage, but still, I am surprised by the calculations. Thi…

I'd imagine it's based on a home with air conditioning. I'm assuming that being in Northern Europe you don't have AC.

Re: Powerwall 2 and Integrated Solar

#132

Post by throwaway1974 »

Loic wrote: post #118

Quick question for the people living in the US (Target customers of the Powerwall). What is your yearly power usage? On the website[0] they put for sizing 10kWh/day/BR. Which means 14600kWh/year for a 4 bedroom house. Here in Germany, working from home with a 4BR+office house, we are using 2550kWh/year. So, I suppose the Tesla sizing is to support a "peak day" usage, but still, I am surprised by the calculations. Thi…

Ireland, 4 bed detached, solar water heater which works well for about 4 months of year, oil heating + wood/turf stove for rest of time. No need for air conditioning here but heat recovery thingie is on all time.

5000kWh last year, tho I have computer(s) on 24x7 due to home office, Comes to about 120€/month

Half of all the bills are just standing charges, and renewable subsidies charges and taxes, and taxes on taxes. Hence adding LED lights, low power appliances etc did little to budge the bills

Re: Powerwall 2 and Integrated Solar

#133

Post by makomk »

andreyk wrote: post #116

His argument about the solar roof starts by equating the situation to how Tesla started out - electric cars were slow and ugly and needed to be sexy and cool to be attractive, and the same is true for solar. Except I highly doubt this is true here - do people really mind the look of typical roof-mount solar? My impression is that the upfront cost is just too high and cost recoup is just too slow. The argument for the…

The reason that solar roofs aren't common is that they're more expensive than rooftop solar. As I understand it, Tesla/SolarCity's argument isn't that they're cheaper than normal solar, it's that they're the same cost as normal re-roofing once you take into account the income from the solar. From the ArsTechnica article: 'In a private conversation with journalists after the announcement, Musk declined to state a price for the roof or a price-per-square foot. He did admit "it's not gonna make sense for somebody to replace a brand new roof with a solar roof." But if your roof needs replacing anyway, he said, the cost/benefit could make sense for many families.'

More specifically, since SolarCity's business model is that they own the solar panels and you're committed to buying electricity produced by them for their lifespan, his argument is that it costs no more than conventional re-roofing + conventional electricity. There is of course the slight downside of you no longer owning the roof over your head, and having to commit to electricity purchases for the next decade or so.

Re: Powerwall 2 and Integrated Solar

#135

Post by botty_throwaway »

beambot wrote: post #122
Uptrenda wrote: post #119

You can buy 12v 250ah deep cycle AGM batteries from China for around $5 per battery -- lets assume another $15 for world-wide shipping. These kind of batteries would have around 3kwh of storage per battery but since you shouldn't discharge them to more than 50% lets also say that you need to double the number of batteries to achieve 14kwh of usable power for 28kwh of total capacity. At that capacity level, you would…

Are you sure about those shipping costs to a residential address...? Professional installation? Process and guarantees from a reputable American OEM? Breakdowns and warranties? I think you're missing a lot of costs beyond the raw materials...

Regarding professional installation, those costs are not factored into the base price. It's an additional cost to both parent's DIY method and the Powerwall.

As for reputable warranties against breakdowns, please check out the fine print of the Powerwall warranty terms and conditions. It's a '10 year warranty' with some very special legalese baked inside that may make you reconsider the cost premium commanded by guarantees provided by a company very adept at lawyering up and navigating regulation.

The warranty (at least in North America) has provisions for voiding warranty claims in off-grid scenarios: during the entire period from installation to claim you must have constant access to the Internet for remote updates. If Tesla detects you go offline, they reserve the right to deny your claim.

In addition, if you use the Powerwall for additional applications besides self-consumption of solar power, you're capped at 18 MWh aggregate throughput before the claim is denied. Consider a 6 KWh solar installation for 5 hours daily charging, with the purpose of selling back energy to the grid (not classified as self-consumption). Now also realize that since this is aggregate throughput, all the charging, smoothing, and then discharging to the grid takes 2x the throughput. How many days warranty do you end up getting from this '10 year warranty'? 18 MWh / (6 KWh * 5 * 2) = _300 days_.

Finally, the warranty specifically says how they may choose your compensation. Could be an outdated refurbished model, but could also be cash market value of a similar system at the date of claim. Given the exponential rate of dwindling costs for energy storage, that's a gamble that in a few years your warranty may just pay out a tiny fraction of what you originally invested in you were sold a lemon.

Tying the luxury price premium to guarantees feels very reminiscent of smartphone insurance... which is almost never a good buy. I'm with parent, let's just be honest here: you're paying for luxury markup -- sexy compact design and a good story.

Re: Powerwall 2 and Integrated Solar

#136

Post by qaq »

Uptrenda wrote: post #129
Uptrenda wrote: post #119

You can buy 12v 250ah deep cycle AGM batteries from China for around $5 per battery -- lets assume another $15 for world-wide shipping. These kind of batteries would have around 3kwh of storage per battery but since you shouldn't discharge them to more than 50% lets also say that you need to double the number of batteries to achieve 14kwh of usable power for 28kwh of total capacity. At that capacity level, you would…

You guys do realize that most of the technology you buy is already made in China so its not like buying "American" is going to be some magical guarantee of quality. You'll find that a lot of the tech companies already have their products manufactured entirely overseas where the price is then marked up several hundred percent and sold to western consumers. Regarding costs: I didn't factor in every possible cost but I…

you did not factor in cost of space

Re: Powerwall 2 and Integrated Solar

#137

Post by sergiosgc »

JBReefer wrote: post #61
andrewtbham wrote: post #13

the cool thing is that they look good... they look like a normal roof at the angle you would see from the street in front of the house, but from above... from the angle of the sun they are transparent and you can see the solar cells. I know some rich people that want solar but their neighborhood associations won't allow it, but I don't think they would not have an objection to these roofs. they look really nice.... I…

This product strategy certainly seems easy to copy, I agree. That's good for humanity and bad for Elon financially (I think that's the point for him, I don't think he cares about money outside of more commas).

I don't think he cares about copies. Tesla is poised to be a battery company, so copies will probably buy his batteries. At least long enough for Tesla to move up the value chain.

Re: Powerwall 2 and Integrated Solar

#138

Post by iotscale »

Loic wrote: post #118

Quick question for the people living in the US (Target customers of the Powerwall). What is your yearly power usage? On the website[0] they put for sizing 10kWh/day/BR. Which means 14600kWh/year for a 4 bedroom house. Here in Germany, working from home with a 4BR+office house, we are using 2550kWh/year. So, I suppose the Tesla sizing is to support a "peak day" usage, but still, I am surprised by the calculations. Thi…

1BR+office (home office with 2 always on computers), air circulation with filtering, around 80 square meters, 2 people, also Germany, 3600kWh/Year (~90€/month)

That could probably triple if we had AC. Far worse if we had electrical heating.

Re: Powerwall 2 and Integrated Solar

#139

Post by Loic »

ascorbic wrote: post #131
Loic wrote: post #118

Quick question for the people living in the US (Target customers of the Powerwall). What is your yearly power usage? On the website[0] they put for sizing 10kWh/day/BR. Which means 14600kWh/year for a 4 bedroom house. Here in Germany, working from home with a 4BR+office house, we are using 2550kWh/year. So, I suppose the Tesla sizing is to support a "peak day" usage, but still, I am surprised by the calculations. Thi…

I'd imagine it's based on a home with air conditioning. I'm assuming that being in Northern Europe you don't have AC.

Effectively, we do not have AC and our heating system is not heat pump based but using the local district heating. This means that this power usage is only for: cooking, lights and computer/tv/etc. appliances.

Re: Powerwall 2 and Integrated Solar

#140

Post by Yaggo »

ascorbic wrote: post #131
Loic wrote: post #118

Quick question for the people living in the US (Target customers of the Powerwall). What is your yearly power usage? On the website[0] they put for sizing 10kWh/day/BR. Which means 14600kWh/year for a 4 bedroom house. Here in Germany, working from home with a 4BR+office house, we are using 2550kWh/year. So, I suppose the Tesla sizing is to support a "peak day" usage, but still, I am surprised by the calculations. Thi…

I'd imagine it's based on a home with air conditioning. I'm assuming that being in Northern Europe you don't have AC.

We use heat pumps as well in Northern Europe, but to transfer heat from outside to inside. You can get even five times more heat for the invested electricity compared to direct (resistive) electric heating. The best winter optimized air-to-air pumps work down to -20 °C (-4 °F) with efficiency ratio over 1. For example, I heat my entire house with a single heat pump through the year. Our average electricity bill is ~100 €/month. There are less than ten days in middle of winter when I turn on extra resistive heaters.

Unfortunately, although in Southern Scandinavia we receive about as much sunlight energy than Northern Germany per year, the peak is in summer when the need of energy is lowest and during three winter months almost no usable energy can be harvested from sunlight, meaning that solar-only powered house would need gigantic battery bank (~100 Tesla Powerwalls) to survive over three darkest months.

Post reply on HN