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    The Audio Impact of Solar Panels and Battery Backup: Introduction, Installation & Initial Listen

     

     

    Introduction

     

    It was a dark and stormy night. Not a creature was stirring, not even a mouse. Now that I’ve hooked you with these clichés, the real saga begins.

     

    The only sound to be heard was the soft patter of sleet and freezing rain covering every exterior surface with a translucent glaze. At 2am, the power went out, not to return, other than for a couple of brief 1-2 hour spells, for 5 days. The ice storm was followed by successive days of snow, more ice, and then, more snow. All this, while temperatures dipped as low as 5º F. Meanwhile, my family and I huddled, lived, and slept around our gas fireplace, thankful we at least had some heat. Wow, you say, winters are tough in Minnesota. Think again, buster. This was Austin freakin’ Texas! Where normal weather in mid-February is mild days in the 60s and cool nights in the 40s.

     

    When power (and water!) finally returned, and we slowly got back to normal, my wife and I had the “talk” about protection. No, not that protection, the one about backup power and resilience from outages. What seemed nice in the past became an imperative now. We were now painfully aware of how unreliable our power grid really was.

     

    Of course, we live in Texas, where natural gas is cheap, as is electricity. The cheapest option, and most resilient to an outage of indeterminate duration, would have been a whole-house backup generator. I had priced a system like this in the past — a snazzy, Generac 22kW — and been quoted $9k fully installed. Well, that was before an actual disaster. Now (April 2021), when I could actually get a contractor to even come out and give me a quote, the price was $18k! Long live American Capitalism! Supply and Demand, Sucka’s!

     

    In any case, my progressive wife and daughters recoiled at the prospect of putting a noisy, smelly, fossil-fuel-burning machine next to our house. Despite the considerably greater cost, the decision was made to invest in solar panels with battery backup. Before you ask about ROI, let me stipulate — we’re not going to break even on this for decades, if ever. Our electric rates are cheap (barely over 15¢/kWh, even at the highest slab of our tiered rates), and we do not have time-of-use rates. There is a whole rabbit hole to go down to discuss ROI, but that’s not the focus of this article. Let me just say - this was not an ROI-driven decision.

     

     

    Solar + Battery Backup System

     

    I will also not go deep into the process of selecting a solar contractor. The same supply and demand economics that was driving the generator guys was also driving the solar guys. I got 3 laughably large bids from local solar contractors, after which I decided to go with Tesla, with their upfront, no-fuss pricing right on the website. I selected a 12.24kW system, with 36x 340W panels, along with 3x PowerWalls, with a total capacity of 40.5 kWh.

     

    Tesla moved quite briskly through the steps of system design and permitting, while I got HOA approval. In early June, all the steps needed to schedule installation were done, but then our utility (Austin Energy, or AE) threw in a 4-month delay to schedule a TDR (temporary disconnect-reconnect). The TDR is needed during install for the Tesla electricians to safely reroute the grid connection. Thus began the wait.

     

    Finally, in late October, the install actually occurred over 2 intense, dawn to dusk days. I was quite impressed with the Tesla crew, both the panel installers and the electricians. I don’t want to wax too lyrical about Tesla, however. There were plenty of issues as well, especially as their communication (phone/email/text) really sucks. Again, this article isn’t about all the design and scheduling issues that are typical in this kind of project. Suffice it to say that at the end of day 2, my system had been tested and was operational. Of course, this just means it is potentially operable, as there are at least 2 steps remaining: AE’s inspection of the work, followed several weeks later by AE’s PTO (permission to operate).  So as of this writing, the story isn’t complete. But don’t worry, I’ll have more to say in a future article!

     

     

    The Installed System

     

    One of the few benefits of the long delay is that in the interim, Tesla rolled out new, more efficient panels that produced 425W, instead of the 340W specified in my original system. This changed my system design down to 29 instead of 36 panels, totaling 12.35kW. This actually worked out very well, because I was able to optimize my design further by ensuring:

     

    • no panels on the least-efficient north-facing roof plane,
    • ~50% of panels could fit on my most-productive south facing roof plane, and
    • No panels on a west facing roof plane that gets significant afternoon shade.

     

    Effectively, I was able to achieve a shade-free install. This is important because of something I haven’t mentioned yet — inverters. Tesla’s system uses string inverters, which makes many installers and well-meaning friends fall over themselves to tell you how micro-inverters are so much better. This is certainly important when shade is a factor, but my install was blessed in that regard. Yet another rabbit hole I would like to avoid going down, but I thought I’d mention it for clarity.

     

    Here is an annotated picture of the electrical part of the system:

     

    Outside Tesla Powerwall.jpg

     

     

    This layout does not reflect what most Tesla systems would look like if installed today in other locales. The separate inverter and gateway boxes now live in a tidy integrated module above the PW proper, in a configuration called the PowerWall +. Also, where allowed, Tesla is using a so-called backup switch. This allows a much simpler and cleaner install, as shown on this page.

     

    As the lead electrician told me, as we were going over the system at the end of day 2, my utility AE (Austin Energy) is apparently very old-school, so requires everything (inverters, gateway, powerwalls) to be broken out, and each protected by emergency shutoff toggle switches. They also use the quite uncommon VOS (value of solar) metering method, as opposed to the almost ubiquitous NEM (Net Metering) method. This requires the installation of a PV meter that measures production from the solar panels. The cutout for this is shown in the annotated picture. The PV meter will go in during (or after?) inspection.

     

     

    How Energy FLows - Quick Orientation

     

    One benefit of AE’s old-school installation requirements is that it allows you to easily visualize the way the system works.

     

    Starting at the far right, you see the ingress of the grid through the main meter. This used to feed my 200A main house panel directly, via the dashed green arrow. This path is now gone. Instead the grid now feeds into, and is one of the inputs to, the brains of the system, the Gateway. This is shown by the orange arrow.

     

    Also feeding the Gateway is a feed from the solar panels. The DC energy from the panels flows down from the roof through the conduits leading to the 2 Inverters (marked INV in the picture). These Inverters then feed AC through AE’s PV meter to the Gateway (blue arrow).

     

    Finally, the 3 PowerWalls, mounted in a line (marked PW) on the left end of the picture, feed AC to the Gateway (note: PW’s have built-in inverters) via the red arrow.

     

    Energy to the main house panel is now fed by the Gateway. Based on demand, instantaneous PV production, and policy settings selected by the user, the Gateway feeds a combination of panel, battery, and grid power to the panel. This is important to remember as we get to the next section on audio considerations.

     

    Also relevant to the audio considerations are two further points. First, as required by AE, the techs also installed a new ground rod during install. My house is of recent construction (built 2000), and had existing grounding in the slab and cold water pipes. This new ground rod (don’t know the gauge, should have asked) goes down about 6 feet. Don’t laugh, I live in the hills of NW Austin, and am basically sitting on a piece of rock. I was actually surprised they got 6 feet deep before hitting rock! Does this grounding improve/degrade sound quality (SQ)? Impossible to say, as I couldn’t do a controlled listening test.

     

    Finally, you can see the 6AWG cable (labelled 6AWG Dedicated Circuit), that I specially sourced from Jim Weil of Sound Application a couple of years ago, running straight down from the main panel and going into the house. That’s because my listening room is right behind the exterior wall shown.

     

     

    Audio Considerations

     

    Finally, we get to the good stuff, I hear you saying! Did you even think about how this would affect your audio SQ?!

     

    Yes, I certainly did. All the time I was waiting for the install, I was in two minds as to which way to go. I knew my dedicated audio circuit provides a huge improvement in SQ, as I described in a forum post at the time.

     

    I could ask the install crew to put my audio dedicated circuit on a bypass panel (only connected to the grid). Or I could take a leap, and see how my SQ changed with solar panels and Powerwalls. I decided to take the leap.

     

    But I needed a listening test during install to know if I’d made a horrible mistake! My rationale was as follows. The biggest concern was whether the Gateway in the path for grid power caused a big degradation in SQ. Here’s why. Even if I found solar panel power through the inverters, or battery power from the Powerwalls to sound like crap, I could always finesse the Gateway to feed only grid power to my system during listening sessions. This is a simple matter of configuration with the Tesla app.

     

    But if grid power, routed through the Gateway, sounded significantly worse than the way it used to when directly connected, this was an irreversible problem. Having decided to take the leap, I needed to know quickly if I’d made a mistake, preferably during the install. This way, if I needed to bypass the audio circuit, I could negotiate something with the electricians while on site.

     

     

    Listening Experiment to Evaluate Gateway Impact

     

    Tesla App.jpgThis was not an ideal A/B test. It involved listening to A and B about 6 hours apart. Moreover, listening test A occurred at 8am, a wholly uncivilized time of day when I’m normally never awake (I’m a night owl). Yet I did this all for you, dear reader!

     

    Baseline (A): Before AE’s truck rolled in to disconnect power, I listened to my go-to test tracks on my system with the grid directly attached to the main panel, as I was used to.

     

    Comparison (B): 6 hours later, after the grid input had been rerouted to the Gateway, and the Gateway feeding my main panel, AE’s techs turned the power back on. At this point, the Gateway could only feed grid power to the panel, as neither the solar panels nor the batteries were even connected. Still, this path included all the additional wire, connections, breakers, relays etc that could contribute to a degradation in SQ.

     

    Result: Well, thank GOODNESS, I could detect no loss of SQ. I admit, a weight lifted off my shoulders, revealing how worried I was about the alternative! Obviously, these tests were conducted about 6 hours apart, but I know my system’s sound so well now, I would have immediately noticed a catastrophic SQ loss. Does this mean I would know if there was a slight SQ loss (1%? 5%? 10%?) I really couldn’t say. To be honest, I was really only concerned with a catastrophic drop in SQ, as a Stereophile reviewer reported earlier this year when he put in a backup generator with a transfer switch.

     

     

     

     

    Conclusion

     

    This is where things stand today, a few days after the install. My house is still powered by the grid, until Tesla crosses a couple more hurdles with the utility, AE.

     

    I am relieved that based on my listening test above, the sonic penalty for allowing my dedicated audio circuit to be fed by the Tesla Gateway is either undetectable or very small. However, it’s still early days, and I’m not making any final pronouncements until I’ve lived with my system for a while!

     

     

    Coming Next

     

    In my next article, I expect to give an update on how things are going with the system. More specifically, I hope to report on the relative SQ (via listening tests) of solar panels, batteries, and the grid. Once my system is fully operational, I will be able to conduct a full comparison test, during a sunny day with plentiful panel production. I will configure the system in 3 ways, so that my house is receiving power from each of these in turn:

     

    • solar panels -> inverters -> gateway -> main panel -> dedicated audio circuit,
    • Powerwalls (builtin inverters) -> gateway -> main panel -> dedicated audio circuit, and
    • grid -> gateway -> main panel -> dedicated audio circuit.

     

    The results ought to be very interesting. Stay tuned.

     

     

    My Listening Setup

     

    Here is a diagram of my listening setup.

     

    Austinpop System.jpg

     

     

     

    Primary System

     

    Music Computer:          Taiko Audio SGM Extreme Music Server, Taiko USB upgrade

    Headphone Amplifier:  Cavalli Liquid Gold

    Headphones:                 Meze Empyrean, Abyss AB-1266 CC, Sennheiser HD800 (SD mod)

    DAC:                                Chord DAVE

    USB to dual-SPDIF:       Audiowise SRC-DX bridge

    Ethernet Switches:        SOtM sNH-10G, Uptone EtherREGEN, Buffalo BS-GS2016 (modded for LPS)

    Power supplies:             Paul Hynes SR7MR3DRXL (dual regulation, 3-rail)  for switches

                                            Sean Jacobs DC-3 for DAVE

    Power Details:                Dedicated 30A 6AWG AC circuit, Sound Application TT-7 Reference Power Conditioner

    Power Cables:               Sablon King (wall to TT-7), Sablon Prince (Extreme),   Cardas Clear Beyond (DC-3, SR-7),

                                             Cardas Clear for all other components

    USB cables:                   Sablon Reserva 2020 USB

    BNC cables:                   High Fidelity Cables CT-2 in Schroeder config, JSSG360’d (DIY)

    Ethernet cables:            Sablon 2020, SOtM dCBL-Cat7, Supra Cat 8

    DC cables:                      Neotech OCC (DC-3), Paul Hynes fine silver (SR-7)

    Interconnects:               Cardas Clear XLR balanced

    Headphone cables:       Transparent Ultra cable system

    Accessories:                  Synergistic Research Tranquility Base XL UEF with Galileo MPC, Synergistic Research MiG 2.0 footers

                                            Taiko Audio Daiza Isolation Platforms

     

     

    Acknowledgments

     

    Many thanks to the following companies for supplying cables and accessories to aid in this evaluation:

    • Cardas Audio, for a full loom of Cardas Clear cables.
    • Transparent Audio, for the Transparent Ultra headphone cable with a full complement of headphones leads and source terminators.

     

     

    About the Author

     

    Rajiv Arora — a.k.a. @austinpop — is both a computer geek and a lifelong audiophile. He doesn’t work much, but when he does, it’s as a consultant in the computer industry. Having retired from a corporate career as a researcher, technologist and executive, he now combines his passion for music and audio gear with his computer skills and his love of writing to author reviews and articles about high-end audio.

     

    He  has "a special set of skills" that help him bring technical perspective to the audio hobby. No, they do not involve kicking criminal ass in exotic foreign locales! Starting with his Ph.D. research on computer networks, and extending over his professional career, his area of expertise is the performance and scalability of distributed computing systems. Tuning and optimization are in his blood. He is guided by the scientific method and robust experimental design. That said, he trusts his ears, and how a system or component sounds is always the final determinant in his findings. He does not need every audio effect to be measurable, as long as it is consistently audible.

     

    Finally, he believes in integrity, honesty, civility and community, and this is what he strives to bring to every interaction, both as an author and as a forum contributor.

     

     

     




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    Cool writeup.  

    Different topic but would be interested in what made the decision to go with Tesla.

    Luckily I live in Williamson county (surrounded by Austin/Cedar Park) and will not have to deal with city utilities when we decide to go the solar route.

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    Very interesting. Thanks a lot @austinpop.

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    33 minutes ago, jcbenten said:

    Cool writeup.  

    Different topic but would be interested in what made the decision to go with Tesla.

     

    One word: cost. Tesla was by far the cheapest. The bids from local solar contractors were all at least $10k higher. 

     

    33 minutes ago, jcbenten said:

    Luckily I live in Williamson county (surrounded by Austin/Cedar Park) and will not have to deal with city utilities when we decide to go the solar route.

     

    Howdy neighbor!

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    The MN Winters are exactly why I insist on having a wood burning fireplace in my house. Sure it's nice and cozy to sit around in the winter, but the worst case scenario we have heat.

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    What's next? Maybe streaming Qobuz via FTTH by local ISP versus SpaceX's Starlink?

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    Really interesting, thanks for sharing. Light years away from when we used to wait till after midnight for "clean power" listening sessions. 

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    I just heard back from my project advisor at Tesla that they don't have any "publicly available" THD spec for the PowerWall. 9_9

     

    However, I did hear from a user on Reddit, who compared his grid and PW output on a 'scope, and made a video. Interesting waveforms!

     

    https://www.reddit.com/r/TeslaSolar/comments/qh2m4s/comment/hj01mma/?utm_source=share&utm_medium=web2x&context=3

     

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    Fascinating, and informative. Thank you! Apropos of nothing, I personally don't find the idea of 5% or 10% to be meaningful while I can see the conceptual appeal. I think it really actually discourages people from discovering how GREAT that 5% really is.

     

    Often, that "5%" is EXACTLY what I am paying $$$ to get because that "x%" is exactly the increase in realism or detail or <fill in your favorite audio attribute> one can hear but that neither words, nor numbers, can realistically do justice to. The resulting emotional engagement is, or is not, greater.

     

    Anyway, keep on exploring the margin, austinpop! More 5%! Thanks again.

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    Congrats Rajiv on the solar install. I looked into doing the same thing but due to the topography where we live in PA, we would get little to no power using solar in the winter and not enough in the summer to make it worthwhile. Even Tesla told us not to do it. As for Mr. Fremer’s issues with his Generac generator, we installed a 27 kw Generac several years ago running on our natural gas line. Same transfer switch as MF and we have no SQ issues at all. I listen during power outages and notice no degradation in SQ. Again, congrats on the solar install. I would do it in a heartbeat but for the topography issues.

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    1 hour ago, PeterG said:

    Great piece!

     

    Just so there are no misunderstandings on the economics for people who may be considering solar--In many states, the economics of solar are extraordinarily good.  In Massachusetts, I have a 6 year payback period and I'm earning over 15% annual return (IRR).  My electric bill, which includes powering my Tesla, HVAC (mini splits), and lights, is usually negative after accounting for incentives from the utility.  Financially, it's the best investment available to a "normal" person--about 2X the stock market, with much less risk.  (This does not include battery backup such as Powerwall)

     

    Hi Peter,

     

    Thanks for raising this point. I was focused on describing my ROI situation in Texas. Of course, in many parts of the country, the ROI is much more compelling, from a combination of:

    • state and local rebates and credits,
    • utility rebates,
    • federal tax credits,
    • true net metering,
    • using batteries for rate arbitrage. with time-of-use rates.

    As I said, there is a whole rabbit hole to go down regarding the ROI of solar and batteries!

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    Great article.  And nice, clean install!   Looking forward to your future findings. 

     

    I don't have a battery backup, so I can only observe sound during the day, when the solar is cranking away, and once the sun has set.  No difference.  I was concerned about the solar monitoring device that runs to my router via the electrical system (the available wifi option is apparently unreliable).  Tested it plugged/unplugged.  No difference.  Not sure if the dedicated lines to my setup are the reason.  

     

    Regarding ROI, I think it was 7+ years to break even in my location.  I enjoy listening for most of the day, yet the most recent month of electricity bill was negative (don't have an electric car yet).   Will continue to follow the cost of battery backup.  When I received a recent quote, my response was:  Now I know why Elon Musk is the richest guy on the planet.  

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    38 minutes ago, Jud said:

    I’d expect THD slightly worse than the 2% maximum required of most utilities for grid power. I doubt it will make much difference, because the major factor is not external power quality, it’s the noise from internal sources like LEDs, small appliances, the refrigerator, etc. (which is why it’s nice to have a separate circuit for the audio system).  And then of course there are interactions within the system.

     

    Congratulations on setting up your solar and battery backup systems. Entirely apart from your audio system, the increased peace of mind will be invaluable.

     

    Our house has a solar photovoltaic system and is prewired for backup batteries on the garage wall when we choose to do that. The house was built “green,” so we needed an installation of less than 4kw capacity to provide 100% of our usage (net metering basis). There’s plenty of room for more (Pueblo style house, flat roof with low parapet that shields panels from street view), so we’ll likely add more when we do batteries.

     

    Wow, if 4kW meets your usage in New Mexico, you must have a really efficient home. Well done!

     

    One of my pending experiments is to chase down what seems like a 1.1kW "ambient" draw in my house. Not sure what accounts for that, but I need to wait until all the civilians in the house are safely away before doing a breaker by breaker analysis. Data is fun!

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    17 minutes ago, austinpop said:

     

    One of my pending experiments is to chase down what seems like a 1.1kW "ambient" draw in my house. Not sure what accounts for that, but I need to wait until all the civilians in the house are safely away before doing a breaker by breaker analysis. Data is fun!

    Maybe the system is using it?

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    33 minutes ago, austinpop said:

     

    Wow, if 4kW meets your usage in New Mexico, you must have a really efficient home. Well done!

     

    Congratulations go to our contractor, former head of the New Mexico Green Builders Association. We talked to a family he built a home for before we decided to go with him, and they said “He’ll listen, so he’ll do it the wrong way if you insist, but first he’ll explain to you why he wants to do it the right way.” 🙂

     

    33 minutes ago, austinpop said:

     

    One of my pending experiments is to chase down what seems like a 1.1kW "ambient" draw in my house. Not sure what accounts for that, but I need to wait until all the civilians in the house are safely away before doing a breaker by breaker analysis. Data is fun!


    https://sense.com/thisissense?utm_source=google&utm_medium=&utm_campaign=Non-Brand-SmartShopping&utm_term=&utm_content=&gclid=EAIaIQobChMIwou_hYX78wIVcm5vBB2mkgfOEAQYAyABEgJNO_D_BwE

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    15 hours ago, Jud said:

    The house was built “green,” so we needed an installation of less than 4kw capacity to provide 100% of our usage (net metering basis).

    4kW or 40kW?  If 4, please share (lots) more details.  Thanks!

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    I have a 2300W grid-tied system, installed 2011 before prices of panels really dropped. I made sure to buy US-built PV panels but the microinverters were made in China. Six inverters failed within the first year and the manufacturer paid to replace all. 
     

    My city has its own power utility. I don’t understand why Public utilities are not the norm. The city has hydro, natural gas, and PV generation, buys the rest on the market including about 10% portfolio in wind. The first, I think, 400 kWh are billed at about $0.10 per kWh and the price is tiered upward with increasing usage. Between the low rates and my relatively expensive system, I figure about 20 years to break even. But that’s not why I did it.

     

    Never once thought about how the system might affect the sonics of my audio system. Maybe grid-tied changes nothing but I didn’t notice any change back in 2011. My wife was concerned about sleeping under the panels above our bedroom but I pointed out the power leaves with the sun.

     

    The Tesla batteries seem cool but I hold Musk in the same regard as Bezos. Just not gonna give those dudes my money.

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    My 2300W system provides about one-half of my annual usage (I’m in northern Utah which gets tons of summer sun but lots of clouds during winter). I can easily imagine an efficient house in NM, with relatively even solar radiation throughout the year, getting by with a 4 kW system.

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