Any solar energy experts here?

dang

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Solar panel and energy question for those interested. (in CA) Solar panels on your roof generate power that is put back onto the grid. You use your energy off the grid and basically get credit for the amount you generate (correct me if I'm wrong). There's lots of talk about taxing solar generation, if not now then in the future. Has anyone ever heard of just using the solar panels to power your HVAC unit? My electric bill isn't all that bad in the winter, at least for now, but in the summer it goes WAY up with the use of our A/C. I've always wondered if you just powered your A/C in the summer with your solar panels it would be a stand alone system off grid. There's obvious limitations, you might have to deal with warmer nights than you want, but I was wondering if others think it's feasible.
 

ablank135

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Not an expert, but I literally initiated a solar installation plan at my house in Illinois today, oddly enough. At least here (and through the technology I'm aware of), you are returning domestically generated electricity to the grid through your utility to get a kWh offset and lower bills, and not "capturing" it to power specific devices. At least that's the predominant model. I am aware of battery-based technologies that can store domestically generated solar up to a capacity point, but I believe that just feeds back to the entire household and is not pointed at powering a specific device--if you think about it as household consumption, it's still addressing the hungry AC unit. Here's a storage article:


BTW, the payback period thanks to federal and state incentives and tax credits here is about 4-6 years, assuming around a 40% reduction in kWh use in my case. California math may differ, of course. It always does.
 

autokunst

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One of my clients owns a solar company that works nationwide - SunPeak Solar. I know they would know the answer, but I don't. I did, however, have another client that was really into solar. He put an array on the project and stored the power in batteries. He then powers his entire house off the batteries. He told be there have only been (2) instances where they ran out of power - over the holidays! He cited that right around xmas the sun has the least amount of presence in the sky, and with 3 generations of family visiting for the holiday their usage was the highest. Not a good combination. He wasn't phased by it at all, but his wife was pretty upset and made him put in a backup generator for future holidays. :D
 

Markos

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I’m not sure if you can legally keep your panels off the grid. My sister-in-law has the leased labels. Came with the house. Works well,

Given that I am getting a new roof I looked into. Project sunroof told me it wasn’t worth it. My neighbor is a director at the electrical company and has a big array on his roof. He installed about 3 years ago when the incentives were better.

 

dang

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Yeah, I understand the concept of generating power on your roof and it goes onto the grid, it doesn't actually power your house. But that's where I see the problem. It's basically a sure thing that government will start taxing solar usage when solar starts taking revenue away in other areas. The only way to stay off grid is to use battery storage or only power specific devices during power generation. I'm at a disadvantage with solar on my house because I have some big trees that block direct sunlight, although the trees help in other ways. The numbers in the formula keep changing at energy costs continue to increase. Gas prices go up, fuel efficient vehicles get more popular. Energy costs go up, solar gets more popular. I've just never liked the idea of utility companies basically using free real estate to create a solar power grid for them. When their grid goes down you don't have any power, even with panels on your roof.
 

dang

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I’m not sure if you can legally keep your panels off the grid. My sister-in-law has the leased labels. Came with the house. Works well,

Given that I am getting a new roof I looked into. Project sunroof told me it wasn’t worth it. My neighbor is a director at the electrical company and has a big array on his roof. He installed about 3 years ago when the incentives were better.

Funny, I used that webpage for my house. Their average monthly cost said I'd save $13k over 20 years. When I put in what my average cost really is it changed to $48k over 20 years. Not sure if that adjusts estimated energy costs over time.
 

boonies

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Thanks for sharing the website @Markos. Calculation on my roof says I will save $1,000 over 20 years…i do lover the tree coverage in the summer, but for solar not so helpful.
 

Markos

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The funny thing is that most panels in my neighborhood are far from the optimal angle. Seattle is super far north and you need the panels to be 48 degrees +- 15 degrees for winter/summer.

Further north than most major Canadian cities.
22CEF8D0-7191-4096-93A6-C238A5B28706.jpeg
 

autokunst

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I’m not sure if you can legally keep your panels off the grid.
I'm not sure about Washington (or California), but we're aware of numerous projects that are not connected to the grid. I don't think any such law exists - at least not in this part of the country. Perhaps to get certain tax credits, that is part of the deal - but not in general.
 

Markos

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I'm not sure about Washington (or California), but we're aware of numerous projects that are not connected to the grid. I don't think any such law exists - at least not in this part of the country. Perhaps to get certain tax credits, that is part of the deal - but not in general.

Looks like CA recently changed their laws
to allow you to go off-grid. Local zoning laws may still prevent. Things seem more spread out by @dang so I bet he is fine.

 

dang

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A friend bought 300 acres in my area years ago and it didn't have grid access without costing a LOT of money. He installed solar with a big storage battery about 20 years ago. He just replaced his battery last year and he has never been on the grid. I don't know of any laws, state or local, that say if you have access to the power grid you have to connect to it. At least not yet.
 

Bmachine

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I installed solar on our previous house in LA about 10 years ago. When we moved to the bay area, I also installed a Tesla system with two Powerwall batteries. The way it works is the panels power the house first and then charge the batteries. When the sun goes down the batteries take over. So, as long as there is enough sun to fully charge the batteries we are completely off grid. It is only if there is not enough sun to feed the house that the system switches to the grid.

If the batteries are fully charged and the sun is still feeding the panels, the power gets fed back to the grid. But there is a false sense of satisfaction there because of the power company sells you electricity at about $.20 per kilowatt but, they only give you $.07 per kilowatt for everything you sent back to the grid.

I’ve never looked at it as a money making or saving proposition. I’ve done it mostly for environmental reasons as well as for energy independence, which is much needed where we live because of frequent power outages.

PS: it’s probably obvious, but when the main power grid goes down, this system automatically switches to island mode and continues powering the house as if nothing had happened. It is completely transparent to the end-user.
 
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CSL177

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As an early solar adopter (we're on our second system in 20 years, 11.5 kWh which produces roughly 125% of our power annually) I've toyed with the freestanding solar/AC idea for quite awhile. My HVAC guy even explored it, suggesting a small split system for the garage and panels sized for max load, plus a battery pack to accept the excess power. I haven't done it (yet) mainly because we have limited space for a battery pack, and what's currently available is pricey. The Tesla Powerwall is $10K which would be hard to amortize for a single application like this... storage in good old fashioned acid cells is the cheap option if you have space.
 

dang

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As an early solar adopter (we're on our second system in 20 years, 11.5 kWh which produces roughly 125% of our power annually) I've toyed with the freestanding solar/AC idea for quite awhile. My HVAC guy even explored it, suggesting a small split system for the garage and panels sized for max load, plus a battery pack to accept the excess power. I haven't done it (yet) mainly because we have limited space for a battery pack, and what's currently available is pricey. The Tesla Powerwall is $10K which would be hard to amortize for a single application like this... storage in good old fashioned acid cells is the cheap option if you have space.
Interesting stuff. One thing I've considered with setting up solar specifically for A/C use is to use a core hybrid battery from a car. We have them here at my work and I know a friend that rebuilds Prius hybrids and restores hybrid batteries. Opens them up, finds the bad cells and replaces them. I would only need the battery to store enough energy to run the A/C unit on and off or two our three hours. Might work, I'll have to ask him what he thinks and run some numbers. The batteries would be free and may be able to use several to make a few good ones.
 

Bwana

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Since we've moved to New Mexico I' too have been kicking around going "off the grid" and using wind (we have gobs of it here) and solar. Not so much as a monetary payback but for eco reasons (we have some massively dirty power plans here) and power reliability.

Most solar companies I've found just want to sell you the basic system that fits on the roof and simply supplements the grid feed. I've not found one that has any depth in technology skills.

I need to find a system integrator that can add together a wind turbine, a solar grid and battery storage with "emergency backup" power from the grid if the wind quits blowing and we have multiple cloudy days (unlikely). I'm talking to a guy on Thursday about some water reclamation systems, he may know a good solar guy. I'll post back if I find out anything.

BTW, Tesla isn't the only one out there. I've used Generac products around the world with great success and I'd assume they are cheaper than paying for the Tesla name.

Generac Batteries
 

autokunst

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Recalling that client I had that was really into solar, he had/knew a lot of information about Tesla batteries. In fact, he essentially referred to Tesla as a battery company. Perhaps that is one of their most significant engineering traits.?. However, he also told me the Tesla batteries, while good, were far too expensive. For his aforementioned project he used lead acid batteries. He had many calculations of cost, usage, replacement timeline, etc. Not advocating for or against (Tesla, or Generac) - just sharing info from/about someone far more knowledgeable than me on the subject.
 

eriknetherlands

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Tesla's powerwall batteries ar made by Panasonic as far as I know.

I've I stalled my own solar array on my garage, 5kwh; enough to power my house year round, 3 small kids, but being in the Netherlands we use gas for heating, and no AC needed.

Having a system that can operate as if off grid, requires specific equipment.
Especially the converters, not all can run in island mode. Most conversters are made for domestic use, and use the 50 hz signal from the grid to generate their own frequency, basically 'fitting' their electrons nicely between the others.
(Which isn't how it works in physics, but for understanding it's a nice analogy)
If the grid quits, these converter quit as well. Second reason is safety; if the grid goes out, parts of a house would still be live, but you wouldn't know where/which.

So, Dang in your case ask specifically for a system that can operate in island mode. It would require dedicated wires to your ac setup.
But I would advice you to install it so that you have the option to switch from island to grid connected at your desire.
You're still making electricity when your AC is off, and the planet will thank you donating that to the grid. (Reminder, half of the dutch live under sea level). Pehaps you even get some income out of it.
If later it ever gets taxed, you just disconnect it, and benefit in summer from your investment and free, green electricity.

In NL the rule is that you dont have to pay taxes on purchase, but only if you register them. So every body registers, it saves 22% tax.
Benefit for the government is they know exactly how much KWh is installed where, and being able to upscale the grid's infrastructure accordingly, but also giving the possibility of future taxation based on capacity.
 
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