Need terms to google for my dream system (solar, battery, hybrid grid).

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Oct 15, 2019
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California
I've been lurking for a couple years here on and off, built my own solar generator two years ago with the knowledge gained and have used it several times to power my fridge. Now I think I'm ready to design a whole-house DIY system with battery backup. But I'm still learning how hard it is to have your cake and eat it. I'm in a housing tract built in the 70's that apparently has poor electrical infrastructure and our power goes out more often than it should. Usually for 12-24 hours.

I would love to just not care about PG&E, somehow magically have power from batteries so I can run the AC and my huge TV with surround sound, but I know I'll have to scale back from that as I learn reality.

Here are my goals, and if y'all could give me good search terms or websites so I can learn what I need to ask more intelligent questions I would really appreciate it.
* Have enough house battery that I can run during the day and charge off peak at night (if needed)
* Charge the batteries and/or supplement grid consumption to avoid higher tier energy charges. I love my creature comforts and use a decent amount of watts.
* Maintain power to key circuits during outages, for up to 48 hours (fridges, internet, lights and some nice to haves).
* feeding power back to the grid is not as important to me, but is also a nice to have.

I'm learning terms like "grid-tie", "hybrid", micro-inverter (not good for batteries I think), etc. What else should I be boning up on! I'm watching Wills videos but it seems many are for off-grid only setups.
 

robby

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How much power do you use per month? The KWh is on the bill.
Can you put Solar panels on the roof or on the property and if so how much space do you have for them?
What size AC are you using? There should be a sticker on the side with the power consumption or at least the model number.
 
Joined
Oct 15, 2019
Messages
45
Location
California
How much power do you use per month? The KWh is on the bill.
Can you put Solar panels on the roof or on the property and if so how much space do you have for them?
What size AC are you using? There should be a sticker on the side with the power consumption or at least the model number.
Between 1000 and 1500 KWh per month
I own the house and I can put panels on. I already have pool heater panels (water is pumped through them) from the 80's that take up a lot of roof space, not sure if those would stay. It's a 5 bedroom house, not sure of the exact size of the AC. I do have it zoned for upstairs and downstairs.
 
Joined
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Messages
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robby

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Between 1000 and 1500 KWh per month
I own the house and I can put panels on. I already have pool heater panels (water is pumped through them) from the 80's that take up a lot of roof space, not sure if those would stay. It's a 5 bedroom house, not sure of the exact size of the AC. I do have it zoned for upstairs and downstairs.
That seems real low, is that the usage when it is occupied?
 

Hedges

I See Electromagnetic Fields!
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Mar 28, 2020
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1500 kWh/month 50 kWh/day is reasonable. 10 kW of PV generation from 12 kW (STC) of panels would do that on average (great for grid-tie net metering)
If you wanted to be off-grid, would likely need much more for short, cloudy winter days.
Panels are cheap. Batteries are expensive and wear out. Cheaper to use the grid as your storage (and small battery to limp by during outages.)

Grid tie can pay for itself in 3 years. If you get a zero-export system, depends on how much is curtailed and not used.
Battery system would only pay for itself if a low-cost DIY or other economical battery. Premium brand batteries cost more than PG&E.

SanTan Solar and eBay have been my main sources.
I use SMA Sunny Island and Sunny Boy. Sunny Boy is a fairly competitive grid-tie inverter. Sunny Island is a fairly expensive battery inverter, but there are liquidation deals (not as cheap as when I got them 20 months ago.)

You didn't list any big motors, which means cheaper lightweight battery inverter might meet your needs. A/C, pool or well pump are heavier loads, need a better inverter.

How much would you like to spend? $:)$
 

robby

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Joined
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Messages
540
1500 kWh/month 50 kWh/day is reasonable. 10 kW of PV generation from 12 kW (STC) of panels would do that on average (great for grid-tie net metering)
If you wanted to be off-grid, would likely need much more for short, cloudy winter days.
Panels are cheap. Batteries are expensive and wear out. Cheaper to use the grid as your storage (and small battery to limp by during outages.)

Grid tie can pay for itself in 3 years. If you get a zero-export system, depends on how much is curtailed and not used.
Battery system would only pay for itself if a low-cost DIY or other economical battery. Premium brand batteries cost more than PG&E.

SanTan Solar and eBay have been my main sources.
I use SMA Sunny Island and Sunny Boy. Sunny Boy is a fairly competitive grid-tie inverter. Sunny Island is a fairly expensive battery inverter, but there are liquidation deals (not as cheap as when I got them 20 months ago.)

You didn't list any big motors, which means cheaper lightweight battery inverter might meet your needs. A/C, pool or well pump are heavier loads, need a better inverter.

How much would you like to spend? $:)$
Brain fat on my part, I just glanced it at and thought he said 150KWh.😞
 
Joined
Oct 15, 2019
Messages
45
Location
California
1500 kWh/month 50 kWh/day is reasonable. 10 kW of PV generation from 12 kW (STC) of panels would do that on average (great for grid-tie net metering)
If you wanted to be off-grid, would likely need much more for short, cloudy winter days.
Panels are cheap. Batteries are expensive and wear out. Cheaper to use the grid as your storage (and small battery to limp by during outages.)

Grid tie can pay for itself in 3 years. If you get a zero-export system, depends on how much is curtailed and not used.
Battery system would only pay for itself if a low-cost DIY or other economical battery. Premium brand batteries cost more than PG&E.

SanTan Solar and eBay have been my main sources.
I use SMA Sunny Island and Sunny Boy. Sunny Boy is a fairly competitive grid-tie inverter. Sunny Island is a fairly expensive battery inverter, but there are liquidation deals (not as cheap as when I got them 20 months ago.)

You didn't list any big motors, which means cheaper lightweight battery inverter might meet your needs. A/C, pool or well pump are heavier loads, need a better inverter.

How much would you like to spend? $:)$
Great info and questions!
I think I'm ok spending up to $10k but less is better. I want to do as much DIY as possible, and my wife is supportive of that.. But as the name says, I'm, impatient, so I might buy one of the batteries Will has evaluated.
I do have a pool and I also have AC. I don't care about the pool during outages, but AC would be nice. Really nice would be internet and my home media setup because I don't like being "unplugged" for too long :)
I learned about the term "Hybrid Inverter" from this video which I'm still working through. It's from 2017 so I'm sure much has changed, but this system seems to be close to what I want (minus the lead acid batteries). I also don't need my panels wired for 360v since they won't be "on the farm". Feeding back to the grid is not my priority (is that what you mean by zero export?)
 

robby

Solar Addict
Joined
May 1, 2021
Messages
540
Great info and questions!
I think I'm ok spending up to $10k but less is better. I want to do as much DIY as possible, and my wife is supportive of that.. But as the name says, I'm, impatient, so I might buy one of the batteries Will has evaluated.
I do have a pool and I also have AC. I don't care about the pool during outages, but AC would be nice. Really nice would be internet and my home media setup because I don't like being "unplugged" for too long :)
I learned about the term "Hybrid Inverter" from this video which I'm still working through. It's from 2017 so I'm sure much has changed, but this system seems to be close to what I want (minus the lead acid batteries). I also don't need my panels wired for 360v since they won't be "on the farm". Feeding back to the grid is not my priority (is that what you mean by zero export?)
A reality check on this.
Some of your goals will not fit within your budget unless you get really DIY and start buying and tearing down used EV power packs.
Even if your 50KWk per day consumption is cut in half to 25Kwh per day your still going to need at least 20 KWh worth of batteries to reliably maintain power while the grid is down for 48 hours. The battery costs alone unless they are totally DIYed are going to eat up 70% of your budget and that is if you use the cheapest LPF packs on the market. Now if your willing to do without the AC you could probably get that cost way down.
Internet and TV almost use no power. Yes Zero export is when your sending nothing back to the grid.
 
Joined
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Messages
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Location
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A reality check on this.
Some of your goals will not fit within your budget unless you get really DIY and start buying and tearing down used EV power packs.
Even if your 50KWk per day consumption is cut in half to 25Kwh per day your still going to need at least 20 KWh worth of batteries to reliably maintain power while the grid is down for 48 hours. The battery costs alone unless they are totally DIYed are going to eat up 70% of your budget and that is if you use the cheapest LPF packs on the market. Now if your willing to do without the AC you could probably get that cost way down.
Internet and TV almost use no power. Yes Zero export is when your sending nothing back to the grid.
I appreciate that, and yeah, 50KW/day is a ton. I can live without AC (I can always go sit in my car or jump in the now colder pool) as long as I can power some fans. I have recently connected an Emporia Vue into my Home Assistant setup, and I intend to add hall sensors to the circuits in my breaker box so I can get a better handle on usage. In the mean time, this is all really great info. I don't mind spending more, and maybe there will be some government rebates to help (even DIY) if I can really make this work well.

Any comments on the Hybrid Inverter setup?
 

robby

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Sol-Ark is one of the leading companies in this area. The Price is high but at least you can get a look at what a complete system looks like and then see what you can live without and then see if there is another Hybrid at your price point.
 
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Hedges

I See Electromagnetic Fields!
Joined
Mar 28, 2020
Messages
8,397
Grid-tie inverter, PV panels, mounting hardware, and balance of electrical equipment can be bought for $1/watt. DIY and labor is free.
So a 10kW system would use approximately all of your $10k budget. Maybe less, there are various prices.

A batteries-optional hybrid would let you put in a very small battery, enough to provide starting surge for A/C and carry small loads at night.

SunXtender AGM cost me $5000 for 20 kWh gross, 14kW usable. You could put in 1/4 of that. But some inverters need a certain ratio of battery to PV to buffer changes in load. My SMA want 5kWh per 1kW of PV, but I have a fraction as much as recommended. (That's where "batteries optional" could work with any size battery.)

Same usable capacity DIY LiFePO4 could be half the price. No-name commercial a bit more than the AGM, name-brand several times the price.
FLA generally less than AGM. Premium brands, sized for several days without sun so shallow cycled, could last 15 to 25 years.
Lithium and lead-acid each have their advantages.

Maybe you want to spend $5k or so on PV to feed grid (look into net metering, and impact of being forced to a different time-of-use rate schedule), and something under $5k on making battery backup work.
Critical loads can be picked up by UPS function. A/C can be enabled if battery reasonably charged. I use interlocked breakers to backfeed balance of property loads when desired.
 

robby

Solar Addict
Joined
May 1, 2021
Messages
540
Grid-tie inverter, PV panels, mounting hardware, and balance of electrical equipment can be bought for $1/watt. DIY and labor is free.
So a 10kW system would use approximately all of your $10k budget. Maybe less, there are various prices.

A batteries-optional hybrid would let you put in a very small battery, enough to provide starting surge for A/C and carry small loads at night.

SunXtender AGM cost me $5000 for 20 kWh gross, 14kW usable. You could put in 1/4 of that. But some inverters need a certain ratio of battery to PV to buffer changes in load. My SMA want 5kWh per 1kW of PV, but I have a fraction as much as recommended. (That's where "batteries optional" could work with any size battery.)

Same usable capacity DIY LiFePO4 could be half the price. No-name commercial a bit more than the AGM, name-brand several times the price.
FLA generally less than AGM. Premium brands, sized for several days without sun so shallow cycled, could last 15 to 25 years.
Lithium and lead-acid each have their advantages.

Maybe you want to spend $5k or so on PV to feed grid (look into net metering, and impact of being forced to a different time-of-use rate schedule), and something under $5k on making battery backup work.
Critical loads can be picked up by UPS function. A/C can be enabled if battery reasonably charged. I use interlocked breakers to backfeed balance of property loads when desired.
He is talking about being able to go 48 hours with the Grid being down and also using solar in the day and shaving off peak hours at night. Do you think FLA or AGM batteries are the best solution if he is going to be using them everyday for peak shaving? I would think Lithium is the way to go and for that 48 hour period off grid I just don't see $5K of batteries cutting it when his normal usage is so high. I guess it all depends on what he is willing to sacrifice on the critical loads panel. Also you did not include the price of the Hybrid Inverter.
 

Hedges

I See Electromagnetic Fields!
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8,397
By the time cycle life is used up,
AGM costs $0.50/kWh
FLA $0.25/kWh
Top-name lithium batteries cost $0.50/kWh
DIY LiFePO4 costs $0.05/kWh
off-brand lithium, including recycled, may approach DIY.

If you're cycling daily to save money, only cheap sources of lithium are cost effective (well, maybe some second-life lead-acid could work.)

Off-grid is easy enough, if you have sunshine. Run everything in daylight, almost nothing at night. It works for A/C, unless too hot in the evening.
GT PV (which would be coupled with a grid-forming battery inverter) costs $0.05/kWh over 10 years, $0.025/kWh over 20 years.
The question is how to economically do the battery/inverter portion. That's why I mentioned batteries-optional hybrids. I don't know how good or long-lasting they are, but also serving as the grid tie inverter, could be pretty economical.
I went the premium route with SMA, but was able to buy my battery inverters for $0.25/kW and PV inverters for $0.10/kW.

Without sunshine, that's when big expensive battery bank comes in. Fossil fuel generator is a cheaper way to make it through the storm.

Batteries for fair-weather solar only need to deliver 1/3 of a day's consumption, to keep lights on at night.
Batteries to last 48 hours without sunshine need to be 6x as big. So the cheapest DIY LiFePO4 costing $0.05/kWh and wearing out in maybe a decade, would cost $0.30/kWh over the first decade. Depending on shelf life might last 20 or 30 years, bringing cost down.

Unless net metering buy/sell rate is terribly different, I consider it cheaper to add more PV and accept the rate, rather than using batteries.
If "buy" price is 3x "sell" price, Putting in 3x the PV is better deal than batteries to store the 1x.
 
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Joined
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Location
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I really appreciate all the responses! And I got what I wanted, which were terms and understanding to ask better questions. I especially appreciate @Hedges detailed questions and answers.
 
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