Wondering if anyone has information on the quality of the AC that a Tesla Powerwall delivers?
I’m considering the notion of putting in a Powerwall, to take advantage of Time of Use pricing, where I’d run the house on batteries during the day, and charge them at night.
I’d expect it to be a high THD electrical source. Inverters pump out distortion. Minimum of 5% is my guess. I’m sure they have available specs.
Further research reveals that it would take around 35 years to pay back the cost of the (15-year-life) batteries with Time of Use savings.
Oh well, it would have been nice to have a backup for our third-world electricity here in Portland.
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@eldrick - yeah, I did a quick check on the batteries earlier and did not have the heart to be a wet blanket… I love living in AZ; paying $0.09/kWhr… benefits of living 75mi from one of the largest nuclear reactors in the USA. I was paying $0.18++/kWhr (tier 1) just 500mi west… AC in the summer @120F is nice @ AZ rates… in addition, my THD does not exceed 2.8% input to PSA P20…
The downside is we are being over-run in the last few years… one effect is our crime has doubled… crazy times. In AZ we see a wrong way entering the highway fatality (TV) at least once a week. Living in CT I never saw that once in 25years… really weird… We also see cars running into buildings at least once a month if not more… very, very rare to see that back home… weird…
I’m actually only paying .065/hour on normal billing, goes to .038 on ToU overnight rate. Lots of hydro power here in Oregon.
@eldrick - OK, those are amazing rates - what is the point of that exercise… curious? I get the $0.038 overnight rates… the infrastructure on top of the batteries would be WTF… to save $0.027 an hr at 12hrs per day at 365 days a year… is $10… am I missing something?
Lets write that up to DWI and technology distractions.
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@watchdog507 - not a hater… actually got me looking at it and I was really curious. I then saw the $kW/hr and said I need to move there… 
I love this forum cause it pushes me to think about stuff I would not think about and for that, I’m grateful… assume the DWI is in reference to AZ wrong way and you would be right. TV said impaired…
You are correct!
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I use 1140 kWh / month. Saving $.27/kWH = around $31 per month savings at todays rates. I used $500/year as long-term savings, assuming that costs will continue to rise. With a $20,000 installation, that’s 40 year payoff.
I’d have solar by now and then storage would make more sense, but I’d have to take out five large trees, and that is prohibitively difficult in Portland.
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@eldrick - yeah, since I am 60 years old, anything more than 15 year payout is a non starter. Figure I will sell by 75. The electric co asked my wife about putting solar panels on our house and we would get a $40 check every month and they would get the electricity. I asked her 15 questions about the liability of that deal. Across the street did it and it looked hideous. Most things on face value seem logical till you open a spreadsheet and start working numbers and what if scenarios. I’m very interested in solar; however, love my low THD and every time I sit down and do the math, I walk away with 15 year recoup as minimum. However, it’s always good to bounce ideas around. Based on $31/ month, $375 a year… and rates going up, charge hold (leakage) decreasing over just 10 years… yeah, a non starter… however, got me thinking about that approach and for that I am grateful.
I have a Solar system utilizing a Fronius Inverter the THD on the grid or via the inverter is the same 2 to 3 %. My P-10 cleans is up to .1 to.2 %. A system would have to have a poor quality inverter to generate 5 % distortion.
@sixpack1- do you find that much savings w/ solar. I found for a quality set up the payback is usually 15+ years and if I were younger, that would be a draw.
I did not purchase my system. I lease it. In 20 years my lease will expire. I prefer the lease as no up front cost and they have to maintain the system should there be any inverter or panel or other system failures. In the long term it will save me money as I have a fixed payment that does not increase as the utility costs will. I asked what happens at the end of the lease and was told I should tell them to come take the system off the back of the house. At that point they would just give me the system.
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@sixpack1- John, thanks… this summer in AZ has set record heat warnings back to back to back. Even when setting up the house for the best possible energy savings, 110-120F you run the AC quit a bit… very good points on the maintenance of the system. What has been the efficiency decline over the years and what is the set point for loss of efficiency versus calling that maintenance. I assume maintenance is broken invertor versus poor performing invertor? Houses in the southwest are tile roof and damage of a roof is a real possibility of which any time someone climbs our roof, I worry… as opposed to roofs back home in the Northeast.
Just set up another appointment today w/ solar company representative to discuss details and a few questions sparked by this thread
- Type inverter and THD (worse case, typical)
- What constitutes maintenance if I go lease, degrading system versus broken (% efficiency threshold)
- Battery bank cost, physicality, benefits and mechanization
- Measurement infrastructure wrt tracking and parameters measured and how they are measured
- Energy buyback if not used or storing in batteries for peak demand (need to analyze)
- All liability aspects of leasing - roof risk, removal…
- Solar efficiency degrading profile for their product
- New panels (technology, near future; year) that increase efficiency substantial… disruptive vs. incremental
Here is some verbiage about efficiency and leasing. The question becomes - define underperforming. I assume they have a threshold efficiency number. In addition, refunding a depreciated panel (% initial cost) at a later date is different than replacing the panel with a new panel. I assume they replace the panel at your request and discount the depreciated panel from a substantially marked up panel (MSRP). In addition is the labor free to make that change… all questions that need to be asked when leasing.
Richard,
Yes the original contract spells out the decline of efficiency over the live of the system. If it does not perform as promised I get refunds. My Panels are Solarworld a very high quality manufacturer. The company that did the installation is Real Goods Solar. They monitor the system and would come to take care of any issue that results in poorer than predicted performance. My contract at spells at Killowatt Hour output for each year of the contract.
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@sixpack1 - thanks for your feedback - every time I sit down to look at solar I investigate the solar panel efficiency (ave is 17%, invertor efficiency ave is 97%); however, I don’t really sit down and start with the APS bill and figure how that will be reduced with adding a $25K solar infrastructure.
So you think your energy bill is all about energy, not so…here is our AZ APS July bill:
$400.78 for JUL we pay
$233.67 for actual energy (peak & off peak) = $0.09/kwhr
$167.11 for all the 27+ services & government crap… $0.07 a kwhr
So, question becomes when you go to solar do you get rid of the added expenses and my assumption is you do not unless you are completely off the grid and I don’t know if they allow that?
How much is your electric bill a month to your energy provider now that you have solar? What is the cost of everything except energy production (adding or removal from grid)?
There are two forms of tax - horizontal and vertical. Governments absolutely love horizontal, they can burry tax on a multitude of different taxes like federal environmental improvement surcharge… while vertical is increasing an overall tax and that shows up very quickly and can be tracked easily… tax sensitivity… 3 cents on 32+ taxes are a lot easier for the cattle to swallow than $96cents overall.
This is very important when you sit with a solar salesman and they ask what your bill is every month. With respect to solar, mine is $233.67 for JUL; however, most would say $400.68… selling you solar is a lot easier when the monthly number is higher. You need to show the salesman the bill and say what part of that bill will you reduce? Then you can compare the benefit of solar…
Every year energy goes up; however, does it really or does the percentage of non energy production to energy production increase… if it is the latter, how does solar help? My bill is close to 50% of buried charges… yet APS claims $0.09/kwhr and they are right if you parse through the bill babble
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Richard,
I pay $142.50 per month fixed for the term of the agreement. I pay $19.60 for the grid connection. In months that production falls off I also pay for any electric purchased from the utility. I have a pool and air conditioning which runs allot from late May to early October. You are paying allot more than I am.
That’s a real issue. My “rate” per kW from PGE is .065, but when I take the total bill and divide by the kWh it comes out to .12.5/kWh, doubling the cost of my electricity.
The difference is taxes, special assessments, and “public purpose” charges from the city, and most of that wouldn’t be affected by a rate reduction.
@sixpack1- I just looked at my yearly and it is $2076… average of $173/month… I just don’t see investing $25K into solar w/ battery, great convertor… to reduce my bill by $75/month… 30 years recoup… my cost is AC summer and less than 500kwhrs in fall, winter, spring… OCT to APR… The summer (MAY/JUN/JUL/AUG) brings an exponential jump of 1500 to 2600kwhrs