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

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

 

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

 

[austinpop]

I just want to re-emphasize that I went into this fully aware — and expecting — sonic degradations any time I was running on the PV panels or on the Powerwall batteries. If the listening tests prove otherwise, I will treat it as an unexpected bonus.

 

That is why the test I described in the article was so crucial. As long as my grid path was not degraded by the install, I could always configure grid power during my listening sessions.

[austinpop]

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!

[austinpop]

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!

[austinpop]

15 hours ago, vortecjr said:

Maybe the system is using it?

 

I've tried the obvious things.  Will let you know what I find.

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23 hours ago, astrotoy said:

However, I could not hear any effect on my audio system either time.

 

53 minutes ago, beetlemania said:

Never once thought about how the system might affect the sonics of my audio system.

 

That's good, and my hope is to find little to differentiate SQ-wise between the 3 sources of power: grid, PV, and battery. However, it will be good to confirm this in  a controlled manner.

 

For those with existing systems, see if you can easily flip between panels and grid (and battery, if you have it), either using software control, or flipping breakers. If so, you can do the comparison with very short delays between modes.

 

I'm curious to hear what your find.

[austinpop]

2 hours ago, Mike Rubin said:

Of course, YMMV, but I wasn't surprised at AustinPop's conclusion that he could live with the solar panels' noise levels.

 

Well, I haven't concluded that yet. That is one of the experiments I've got lined up!

[austinpop]

1 hour ago, AudioDoctor said:

I am sitting here thinking about this. We have been thinking about putting solar panels on the roof for a while now, and I was thinking why not put the house on the solar circuit, and use another dedicated circuit for the audio system and separate the two? Then, while not being able to listen to music during a power outage, you wouldn't have any potential sound quality issues to worry about either.

 

Yes, that was the safe option I considered, by putting the audio circuit(s) on a bypass panel that is only powered directly by the grid.

 

But where's the fun in "safe!" 😎

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56 minutes ago, AudioDoctor said:

 

I am spitballing ideas here, but it seems to me that separating the two would be the best of both worlds. Additionally, unless you are getting enough energy to refill your batteries every day, then during a power outage I think being smart about power usage would be a good idea as storms get crazier and times to fix damage gets longer. A Class A Pass Amp, even if its the smallest one, would probably drain batteries in no time. But for that brief glorious amount of time, we would also be warm...

 

There are so many considerations, and this is why I wrote this article -- to tease apart the audio considerations from the functional ones. Just as an aside, and I expect this is well known in this crowd, a solar installation without battery backup is not functional during a power outage. Since there is nowhere for panel generation to go other than the house, utilities require PV panels to turn off during an outage, so as not to zap hardworking lines people working to restore power.

 

With regard to audio considerations, there are several use cases:

• During normal operation, instantaneous power to the audio circuits flowing from one, or a combination of:
  • the grid,
  • PV panels, or
  • Batteries.
• During a power outage, instantaneous power to the audio circuits flowing from one, or a combination of:
  • PV panels or
  • Batteries.

I'm personally not sure to what extent I would be listening to audio during an outage, certainly not with Class A's!

 

Still, the experiments I have postulated apply to both. How does SQ differ when instantaneous power to the audio gear is flowing from each of:

• the grid,
• PV panels, or
• Batteries?

Some anecdotal posts here have already indicated -- no audible difference. I will see what my listening tests tell me. Perhaps the same. Perhaps better with batteries? Wouldn't that be something!

[austinpop]

1 hour ago, cjf said:

Hello @austinpopand great article.

 

I was curious of a few details on the 12kW system you described. Was this figure based on your daily usage and if so did you use your Pre Solar utility bill averaged out over several months or more to come up with this size system for your house?

 

I'm also curious to know what the expected run time is of the system powering the home after grid power goes out?

 

All of this is part of the sizing process you would go through when you solicit bids. You can always give the solar contractor just the info they ask for - usually a recent utility statement with usage data. But I would assert that AS members are curious and motivated enough to do their own research.

 

Check your account info on your utility provider. If it's like mine, they should have usage data for the last 12-24 months. Crunch the data to get at least a rough estimate of:

1. your ave/max daily consumption in kWh during different periods:
   • in summer when your AC is running the most
   • in winter when your heat is running the most
   • in spring/fall, when neither is, when you should have the least daily consumption.
2. your average annual consumption in kWh. You can use this to compare against solar designs, as all such designs will give you an estimated annual solar production.
3. your average monthly electric bill. 

These data can help you - both with ROI/break-even analysis of cost, as well as sizing:

• for example, how does your battery capacity match your average daily consumption? This will give you an estimate of your outage resilience.

A local solar contractor will customize a bid for your situation, and you can iterate. Tesla, to keep costs low, offers systems only in 4 fixed sizes: 4.25kW, 8.5kW, 12.75kW, and 17kW. Although even that isn't strictly true, as it is possible to pick a size and then ask for additional panels. The more you educate yourself, the better prepared you will be. Well, obviously!

 

1 hour ago, cjf said:

I suspect that at some point in the near future I may be considering a full solar setup without grid to power a house I plan to build located deep in the Colorado wilderness. There is grid power available to my 20acre parcel there but based on a recent estimate from the power company it will cost about $20K to pull a line about 700ft onto the property. This is a tough pill to swallow when Solar power potential in that area is very high also. My concerns with a full solar only setup though have always been a big question mark due to this crazy audio hobby of ours. One fear being how big of a system it would take to maintain the usage of my current system without compromises and if that dollar figure would far exceed the cost to just have grid power pulled onto my land.

 

 

 

Nice!

 

What you're suggesting is an off-grid installation, and there are different considerations for these. On the one hand, not having to satisfy a utility about the size and design of your system is liberating. However, you also have to be more resilient - there is no grid to supply energy if your panels aren't producing in the dark of winter, and your batteries are depleted. I don't claim to know how to size this, so it's worth researching off-grid systems. You will also want to have a generator as an alternate source of power for complete resilience.

 

Whether or not this power is clean enough for audio is definitely a question. I worry most about the generator.

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Progress update: My system finally passed inspections and received PTO!