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I'm going to install a 9kW solar grid on my roof in the next couple of months - capital cost is ~$40K USD. Without the Power Wall, I'd be selling power back to

I'm going to install a 9kW solar grid on my roof in the next couple of months - capital cost is ~$40K USD. Without the Power Wall, I'd be selling power back to the utility at around $0.10 / kWh, and buying it back at $0.09 / kWh in the evenings. The Power Wall will also let me endure grid outages as well (you can't run your house on your solar panels directly). I'm really curious about what the end-user cost is going to be for one of these batteries, after distributor markup and utility company rebates. Would be interesting to see if it pays for itself over the 10 year lifespan of the batteries. I just reserved one.

hayksaakian 11y ago
Is it really worth it if it really takes 10 years to break even (and that's the lifespan as you mentioned)? That's like giving someone a 10 year 0% interest loan. Maybe you're better off buying a bunch of Tesla stock with that money if you think they'll stick around that long.
- TaylorAlexander 11y ago
  If you're only looking at it from a financial perspective, it may not be "worth it" (I haven't done the math). But if you want to pay a little to be able to have reliable power from unreliable sources, then it could be "worth it". It may save you zero dollars over ten years, but during that time you're provided the service from this system.
  - 2muchcoffeeman 11y ago
    But even if the life time cost for the energy is the same, if you can afford the initial payment, why wouldn't you do it? Especially if there are other advantages to the newer technology?
    - IanCal 11y ago
      > But even if the life time cost for the energy is the same, if you can afford the initial payment, why wouldn't you do it? Especially if there are other advantages to the newer technology? There's an opportunity cost. You'd have to weigh the lost gains you could make elsewhere to the advantages.
sremani 11y ago
$40K for 9kW solar sounds really expensive, I advice you to shop a bit or consider Solar lease. I have a 10 kW plant from SolarCity installed in late 2013. It is a prepaid 20 year lease, meaning I own the electricity and they own the panels, and the total cost (including installation, pv, inverters) to me is about 10K. You seem to be getting a 1 cent more for the electricity, so your only motivation for this must be to have a back-up. But the 7kW powerwall is daily cycle, it may be a OK backup but not beyond a day or two.
- localhost 11y ago
  Where I live (WA state USA), there are some crazy tax incentives here for solar. Rough math: 1. 30% rebate on federal income tax, so that's $12K back in the first year. 2. $0.54 / kWh WA state energy production credit which is capped at $5K / year. The estimated power production of a 9kW array over 1 year should get me pretty close to $5K back. The production credit expires in June 2020, which means that best case I get $25000 back from the state. Without factoring in energy cost savings, I nearly break even in 5 years. Energy cost savings are somewhere in the neighborhood of $1200 / year with solar. If the only rationale was energy savings, it's not a good investment. However, the tax incentives make it very attractive indeed. More details on WA state incentives here: http://www.solarpowerrocks.com/washington/ http://www.solarpowerrocks.com/washington/
  - sremani 11y ago
    That is some killer state energy production credits. Now your plan makes complete sense.
grecy 11y ago
> 9kW solar grid on my roof in the next couple of months - capital cost is ~$40K USD That's crazy expensive. My parents just installed 5kW last month in Australia for $10k AUD (and the government rebated them $5k AUD) so their out-of-pocket was $5k, or $1k / kW, fully installed, including the inverter.
- drcross 11y ago
  As someone from a country that gets less sunlight, how do you know the difference between good solar cells and less efficient ones?
  - grecy 11y ago
    Get quotes from a few different places, and read the specs on the panels they're offering.
darkstar999 11y ago
How many decades is the ROI on that?

hayksaakian 11y ago

Is it really worth it if it really takes 10 years to break even (and that's the lifespan as you mentioned)? That's like giving someone a 10 year 0% interest loan. Maybe you're better off buying a bunch of Tesla stock with that money if you think they'll stick around that long.

TaylorAlexander 11y ago
If you're only looking at it from a financial perspective, it may not be "worth it" (I haven't done the math). But if you want to pay a little to be able to have reliable power from unreliable sources, then it could be "worth it". It may save you zero dollars over ten years, but during that time you're provided the service from this system.
- 2muchcoffeeman 11y ago
  But even if the life time cost for the energy is the same, if you can afford the initial payment, why wouldn't you do it? Especially if there are other advantages to the newer technology?
  - IanCal 11y ago
    > But even if the life time cost for the energy is the same, if you can afford the initial payment, why wouldn't you do it? Especially if there are other advantages to the newer technology? There's an opportunity cost. You'd have to weigh the lost gains you could make elsewhere to the advantages.

sremani 11y ago

$40K for 9kW solar sounds really expensive, I advice you to shop a bit or consider Solar lease. I have a 10 kW plant from SolarCity installed in late 2013. It is a prepaid 20 year lease, meaning I own the electricity and they own the panels, and the total cost (including installation, pv, inverters) to me is about 10K. You seem to be getting a 1 cent more for the electricity, so your only motivation for this must be to have a back-up. But the 7kW powerwall is daily cycle, it may be a OK backup but not beyond a day or two.

localhost 11y ago
Where I live (WA state USA), there are some crazy tax incentives here for solar. Rough math: 1. 30% rebate on federal income tax, so that's $12K back in the first year. 2. $0.54 / kWh WA state energy production credit which is capped at $5K / year. The estimated power production of a 9kW array over 1 year should get me pretty close to $5K back. The production credit expires in June 2020, which means that best case I get $25000 back from the state. Without factoring in energy cost savings, I nearly break even in 5 years. Energy cost savings are somewhere in the neighborhood of $1200 / year with solar. If the only rationale was energy savings, it's not a good investment. However, the tax incentives make it very attractive indeed. More details on WA state incentives here: http://www.solarpowerrocks.com/washington/ http://www.solarpowerrocks.com/washington/
- sremani 11y ago
  That is some killer state energy production credits. Now your plan makes complete sense.

grecy 11y ago

> 9kW solar grid on my roof in the next couple of months - capital cost is ~$40K USD That's crazy expensive. My parents just installed 5kW last month in Australia for $10k AUD (and the government rebated them $5k AUD) so their out-of-pocket was $5k, or $1k / kW, fully installed, including the inverter.

drcross 11y ago
As someone from a country that gets less sunlight, how do you know the difference between good solar cells and less efficient ones?
- grecy 11y ago
  Get quotes from a few different places, and read the specs on the panels they're offering.

darkstar999 11y ago

How many decades is the ROI on that?