Powerwall 2 and Integrated Solar • Hacker News Board

Re: Powerwall 2 and Integrated Solar

#251

Post by kwhitefoot » Sat, Oct 29, 2016, 2:10 PM UTC

espadrine wrote: post #177

Yaggo wrote: post #140

Earlier quoted context omitted.

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 ~1…

I heard great things about heat pumps efficiency-wise, but that their downside were noise. However, that information is dated because I haven't looked into it in a long time. Has that improved? I'd expect the market in Scandinavia to be much more developed than in my country.

Depends how much you pay. The last time I looked a simple air to air pump the cheapest was 31dB and the most expensive was 21dB. So very quiet indeed.

About one in five houses have heat pumps where I live (about 40km south of Oslo) and I can hear them humming as I walk past but of course they are not the latest models. Still they are orders of magnitude quieter than the units outside the flat I rented in Cary, NC ten years ago.

Re: Powerwall 2 and Integrated Solar

#252

Post by ap22213 » Sat, Oct 29, 2016, 2:17 PM UTC

antisthenes wrote: post #184

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…

The reason their calculations are so high is because in the US, typical houses are made as cheaply as possible, pretty much with paper, plastic and vastly insufficient insulation. That may have changed in the recent years, but holds true for most residential properties built before 1980.

I've lived in a lot of cities through the 'rust belt', and I'd estimate that half if not more of pre-1970 houses had no insulation at all.

Re: Powerwall 2 and Integrated Solar

#253

Post by celticninja » Sat, Oct 29, 2016, 2:26 PM UTC

mrfusion wrote: post #243

celticninja wrote: post #231

Earlier quoted context omitted.

What's the running cost of a huge ups?

I don't understand. Why would it cost anything to run it? It's just a big battery. Maybe a small charge to keep it topped off?

It was a genuine question, I have ever used or needed one, therefore I have little to no idea how they operate.

Re: Powerwall 2 and Integrated Solar

#254

Post by rsp1984 » Sat, Oct 29, 2016, 2:28 PM UTC

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…

Me in my 2BR apartment: 550 kWh / year. My startup office (3 developers and a lot of computers): 600 kWh / year.

Not including heating. Location: Wiesbaden, Germany.

I have a car but hardly use it. I go to work by bike every day. Guess I'm not quite the target audience for this powerwall thingy :-)

Re: Powerwall 2 and Integrated Solar

#255

Post by [deleted] » Sat, Oct 29, 2016, 2:39 PM UTC

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…

[deleted]

Re: Powerwall 2 and Integrated Solar

#256

Post by DeBraid » Sat, Oct 29, 2016, 2:42 PM UTC

Many Powerwall 2's can be combined to reach potentially unlimited scale. Tesla working with SCE to build an 80 mWh Powerwall 2 stack.

Utility power required to partner with local generators. Bright future for both rooftop and Big Utility.

Solar Roofs

Solar roofs superior to normal roof? Can they look better and costs less. Maybe.

Make solar panels look like roof shingles. A textured glass tile contains/covers (?) the solar cells.

Hydrographic printing allows each tile to look unique, so the roof/house looks beautiful. No two roofs will be the same.

From street-level, it looks opaque, but is transparent to Sun.

Re: Powerwall 2 and Integrated Solar

#257

Post by mrfusion » Sat, Oct 29, 2016, 2:46 PM UTC

celticninja wrote: post #253

mrfusion wrote: post #243

Earlier quoted context omitted.

I don't understand. Why would it cost anything to run it? It's just a big battery. Maybe a small charge to keep it topped off?

It was a genuine question, I have ever used or needed one, therefore I have little to no idea how they operate.

It's just a big battery that you can plug things into full time. When power goes out it instantly switches to battery power. It recharges when the power comes back.

Re: Powerwall 2 and Integrated Solar

#258

Post by tghw » Sat, Oct 29, 2016, 2:48 PM UTC

guruz wrote: post #188

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…

It's no wonder that the EU has half co2 emission per capita than US, given the inefficiencies in US power consumption, cars etc. https://en.wikipedia.org/wiki/List_of_countries_by_carbon_di...

A lot of it has to do with geography. Europe is quite a bit further north, and doesn't experience some of the heat that the US does.

It always helps me to remember that Rome is further north than New York.

Re: Powerwall 2 and Integrated Solar

#259

Post by mhenr18 » Sat, Oct 29, 2016, 2:48 PM UTC

Brakenshire wrote: post #190

snarfy wrote: post #173

Earlier quoted context omitted.

It's really going to depend on the location in the US. When I was living in the southwest, my energy bill per month was ~$500 for a 4 bedroom house. A/C eats a lot of power. After moving to the northwest, my bill is around $80/mo.

To convert that to kWh, assuming a 10-15c/kWh rate, that would equate to 40,000-60,000 kWh per year in the SW and 6,400-9,600 kWh in the NE. My figure for a 4 bed house in the UK is about 4,800 kWh per year.

I'm unsure about the US but I know that where I live a solid third or so of my power bills are a fixed rate that you pay to access the grid (so pretty much line rental). It doesn't feel to me like that's a particularly unique situation.

So it's worth keeping in mind that the actual power usage figure may be a fair amount lower, and that your SW calcs are a bit of a worst case estimate.

Re: Powerwall 2 and Integrated Solar

#260

Post by wilwade » Sat, Oct 29, 2016, 2:49 PM UTC

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…

Another data point. Past 12 months we're at 22,000 kwh. Average of 60kwh a day. Older 4 br house with people almost always in it. USA, TN.

I think the main difference for us is that my wife and some of the kids are at home almost all the time and we kept the house warmer for the baby this winter.