DIY net metering system for under $8,000.00 United states.

Bob The Builder

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The system I will remove! Smart meter adds the power I made and not subtract it. Thats without going through the smart meter and being no where near house usage. Meter in picture is my meter 100 foot from my electoral company meter!
 

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Hedges

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But my energy company only pays 0.02 per KWH and charge 0.12 per KWH. So I would like to store some of the power my panels produce in batteries for night time use and not sell it all for just 0.02 a KWH.

If you "store" power in the grid for later use, you pay $0.10/kWh for storage.

Here are my estimates of battery costs (over cycle life, assuming they last according to spec or 10 years of daily cycling, whichever comes first.)

$0.50/kWh name brand lithium
$0.50/kWh AGM
$0.25/kWh FLA
$0.05/kWh DIY LiFePO4

There are some lower priced "other" brand lithium and recycled cell batteries which may approach DIY. But I don't think they'll be less than $0.10/kWh.

Is your utility rate $0.12/kWh regardless of how much you use or when?
I think DIY grid-tie costs $0.025/kWh, so you can install excess to some extent; it's OK to throw away some power if you can make power for 1/5th of utility rates. But at some amount of installed PV, the savings will stop increasing, then drop again with higher capacity.

Shifting loads to use power when you make it can help, like running a well pump or water heater, or charging an EV, when you have surplus production.
 

Hedges

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Thanks sounds like a good system I can add to as I like. Panels would go on my Shed 100 foot away from the house. I have underground cables they are three #2 Copper cable to my 100 amp sub electrical panel in the Shed. I have two neighbors who have a solar systems leased. Does not sound like a good deal to me. Anyway so net metering is being done in the neighborhood.

100A panel? Or 125A panel with 100A breaker?
"120% rule", main breaker + PV breaker can be up to 120% of busbar rating.
A 125A panel with 100A breaker can have 125A x 1.2 = 150A, 150A - 100A = 50A PV breaker.
Loaded 80% (for continuous use), 40A at 240V = 9600W

If your main panel is rated 200A and has 200A breaker, 200A x 1.2 = 240A, 240A - 200A = 40A breaker feeding sub-panel (and backfed with PV).
40A x 80% = 32A continuous, 32A x 240V = 7680W. That could support a 7.7kW Sunny Boy.

But notice you could only have a 40A breaker feeding the 100A sub-panel.
If main panel is 225A and breaker 200A, then a 70A backfeed breaker is allowed.
 

Sanwizard

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If you "store" power in the grid for later use, you pay $0.10/kWh for storage.

Here are my estimates of battery costs (over cycle life, assuming they last according to spec or 10 years of daily cycling, whichever comes first.)

$0.50/kWh name brand lithium
$0.50/kWh AGM
$0.25/kWh FLA
$0.05/kWh DIY LiFePO4

There are some lower priced "other" brand lithium and recycled cell batteries which may approach DIY. But I don't think they'll be less than $0.10/kWh.

Is your utility rate $0.12/kWh regardless of how much you use or when?
I think DIY grid-tie costs $0.025/kWh, so you can install excess to some extent; it's OK to throw away some power if you can make power for 1/5th of utility rates. But at some amount of installed PV, the savings will stop increasing, then drop again with higher capacity.

Shifting loads to use power when you make it can help, like running a well pump or water heater, or charging an EV, when you have surplus production.
Hmmm. What math are you using for KWh costs? My first DIY Lishen 280ah bank with the BMS and cables/fuses came to about $2000 in Feb. Its more like $2300 now. 48x280= 13440WH. 2000/13440 is .148. What cells are you using to get to .05? I am intrigued!
 

Hedges

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48 x 280 = 13440
$2300/13440 = $0.17/Wh
That's $170/kWh of capacity.

How many cycles can you get out of them?
If they do last 3650 cycles (a decade of daily 100% cycling), it comes to $0.05/kWh of use.

(of course you would cycle a bit less than 100% each day, maybe 80% or 90%.)
The wild card is whether these cells really last 2500 or 6000 cycles as advertised.
One independent test of many brands of batteries, 95% failed and had to be repaired or replaced. So I wouldn't bet on more than 20% of claimed life, and consider anything above that a bonus.
Maybe it's BMS that fails and cells are OK, in which case it can be repaired economically. So long as the failure mode doesn't let cells over/under charge.

PV on the other hand can reasonably last 25 to 40 years. Although, some have issues which cause degradation far earlier.
Inverters ought to last 10 years, will likely do 20 years.
I came up with $0.05 assuming 10 years, $0.025 assuming 20 (I miss-stated 10 years earlier.) If inverter needs replacement, $0.03/kWh over 20 years.
The math is $1/watt, and 5.5 hours effective sun per day.
 

Sanwizard

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Without A/C on but two refrigerators, TV, lights and fans on also outside flooded light on. Its night time.
Hmm. I am sitting next to a window AC which is on, fridge, lights, TV, Sonos system, outdoor lights, laptops, and all my chargers, and I am using 0.61KW.
Granted my TV and all my lights are LED, but I have a nice LG fridge. Perhaps you should turn everything off, and make sure there are no ghost loads( I had a neighbor sneaking power from behind my barn outoor outlet) then turn on one appliance at a time to see what is pulling all that power. My Emporia energy monitor has the two main line monitors plus 16 additional CT's in the panel, so I can get fairly granular. My barn apartment and lights were pulling a lot, but that is totally off grid now on 26KW of Lifepo4 battery and two LV6548's, with 16 Qcell panels.
The LV's can actually run both the barn and the house, but I have not extended the power yet.
 

Sanwizard

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48 x 280 = 13440
$2300/13440 = $0.17/Wh
That's $170/kWh of capacity.

How many cycles can you get out of them?
If they do last 3650 cycles (a decade of daily 100% cycling), it comes to $0.05/kWh of use.

(of course you would cycle a bit less than 100% each day, maybe 80% or 90%.)
The wild card is whether these cells really last 2500 or 6000 cycles as advertised.
One independent test of many brands of batteries, 95% failed and had to be repaired or replaced. So I wouldn't bet on more than 20% of claimed life, and consider anything above that a bonus.
Maybe it's BMS that fails and cells are OK, in which case it can be repaired economically. So long as the failure mode doesn't let cells over/under charge.

PV on the other hand can reasonably last 25 to 40 years. Although, some have issues which cause degradation far earlier.
Inverters ought to last 10 years, will likely do 20 years.
I came up with $0.05 assuming 10 years, $0.025 assuming 20 (I miss-stated 10 years earlier.) If inverter needs replacement, $0.03/kWh over 20 years.
The math is $1/watt, and 5.5 hours effective sun per day.
Ahhh. Now I get it. I forgot the TIME angle!
 

Bob The Builder

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100A panel? Or 125A panel with 100A breaker?
"120% rule", main breaker + PV breaker can be up to 120% of busbar rating.
A 125A panel with 100A breaker can have 125A x 1.2 = 150A, 150A - 100A = 50A PV breaker.
Loaded 80% (for continuous use), 40A at 240V = 9600W

If your main panel is rated 200A and has 200A breaker, 200A x 1.2 = 240A, 240A - 200A = 40A breaker feeding sub-panel (and backfed with PV).
40A x 80% = 32A continuous, 32A x 240V = 7680W. That could support a 7.7kW Sunny Boy.

But notice you could only have a 40A breaker feeding the 100A sub-panel.
If main panel is 225A and breaker 200A, then a 70A backfeed breaker is allowed.
I'm not understanding everything you are saying. Ok I have a house meter pan and 200 amp panel. In my house panel I have a 100 amp breaker that feeds power to my Shed via three #2 copper cables that run underground a 100ft. At the 100 amp panel in my Shed the main breaker is 100 amp. In my Shed I have a refrigerator, lites, duplex recepticals, commercial air compressor, welding machines etc. Most this stuff is rarely used. So how much power can I back feed and what size breakers would I need?
 

Bob The Builder

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Hmm. I am sitting next to a window AC which is on, fridge, lights, TV, Sonos system, outdoor lights, laptops, and all my chargers, and I am using 0.61KW.
Granted my TV and all my lights are LED, but I have a nice LG fridge. Perhaps you should turn everything off, and make sure there are no ghost loads( I had a neighbor sneaking power from behind my barn outoor outlet) then turn on one appliance at a time to see what is pulling all that power. My Emporia energy monitor has the two main line monitors plus 16 additional CT's in the panel, so I can get fairly granular. My barn apartment and lights were pulling a lot, but that is totally off grid now on 26KW of Lifepo4 battery and two LV6548's, with 16 Qcell panels.
The LV's can actually run both the barn and the house, but I have not extended the power yet.
I will try that in the morning. It could be my monitoring system not reading correctly!
 

Hedges

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I'm not understanding everything you are saying. Ok I have a house meter pan and 200 amp panel. In my house panel I have a 100 amp breaker that feeds power to my Shed via three #2 copper cables that run underground a 100ft. At the 100 amp panel in my Shed the main breaker is 100 amp. In my Shed I have a refrigerator, lites, duplex recepticals, commercial air compressor, welding machines etc. Most this stuff is rarely used. So how much power can I back feed and what size breakers would I need?

Each panel has a busbar with some rating. We aren't allowed to run more current through it than the rating. Putting a backfed breaker at far end of the panel means current from PV is flowing the opposite direction as current from main breaker, so it subtracts rather than adds. However, the authors of NEC were afraid in the future someone might relocate the backfed breaker adjacent to main breaker, resulting in the currents adding. So, they put a limit on it, total 120% of busbar rating. That might get hotter, probably not cause a fire. Without this concession, if a 100% limit, most couldn't add any PV.

Decide which panel you want to feed PV into. Determine its busbar rating, and main breaker rating (you might substitute a smaller main breaker if that helps.) Main breaker rating + PV breaker rating can't be more than 1.2x busbar rating. Same math for every panel up the line including main panel.

I think you have two panels (at first I thought a 3rd). You could always change shed panel or branch to two panels there, so it isn't the limiter.
Key question is what busbar rating your "200A" main panel has. Mine is Square-D QO, and busbar is 225A. 225A x 1.2 = 270, so with 200A main breaker, I can have a 70A breaker feeding PV, or feeding another panel that has PV and some loads.

You can probably change the 100A breaker to either 70A (if 225A busbars in main panel), or 40A. That's a bit low for the shop tools; I use 50A breaker for my buzz box. You may be able to reduce main panel breaker from 200A to 150A (of course need utility to disconnect power while you do.)

But wait - meter panel and 200A main panel? Is there a 200A breaker in the separate meter panel? If so, that's great. That's what I have. If so, put a 200A breaker in the main panel and separate 100A fused disconnect feeding the shed. Then it is pretty much unlimited. (the 200A breaker in main panel is to prevent 200A from grid and 100A from fused disconnect together feeding 300A into main panel.)
 

DThames

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This is my second post here, my first post was about a Frankenstein grid tie system I was having problems with. I wasted $1,000 to find out this is not the way to go. No one commented on it! I have $8,000.00 left and don't want to make the same mistake. Im looking for a DYI small net metering system that can be expanded easily. Something with maybe micro inverters. I want to start small with my limited funs for now. I'm looking at a lithium battery backup for later, with the grid tie system as my energy company only gives $0.02 per KWH and charges $0.12. Tax credits do not apply to me as We are retired and living on investments and social security. I like the idea of a wind generator as well. I would like to get everything from one company that would walk me through everything including the perments and installation. What companies are doing this that members here have used with No problems? Im ready to get started soon.
Micro inverters are good for expansion at a later date. Micro inverters are not for off grid or emergency power.
 

Bob The Builder

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Each panel has a busbar with some rating. We aren't allowed to run more current through it than the rating. Putting a backfed breaker at far end of the panel means current from PV is flowing the opposite direction as current from main breaker, so it subtracts rather than adds. However, the authors of NEC were afraid in the future someone might relocate the backfed breaker adjacent to main breaker, resulting in the currents adding. So, they put a limit on it, total 120% of busbar rating. That might get hotter, probably not cause a fire. Without this concession, if a 100% limit, most couldn't add any PV.

Decide which panel you want to feed PV into. Determine its busbar rating, and main breaker rating (you might substitute a smaller main breaker if that helps.) Main breaker rating + PV breaker rating can't be more than 1.2x busbar rating. Same math for every panel up the line including main panel.

I think you have two panels (at first I thought a 3rd). You could always change shed panel or branch to two panels there, so it isn't the limiter.
Key question is what busbar rating your "200A" main panel has. Mine is Square-D QO, and busbar is 225A. 225A x 1.2 = 270, so with 200A main breaker, I can have a 70A breaker feeding PV, or feeding another panel that has PV and some loads.

You can probably change the 100A breaker to either 70A (if 225A busbars in main panel), or 40A. That's a bit low for the shop tools; I use 50A breaker for my buzz box. You may be able to reduce main panel breaker from 200A to 150A (of course need utility to disconnect power while you do.)

But wait - meter panel and 200A main panel? Is there a 200A breaker in the separate meter panel? If so, that's great. That's what I have. If so, put a 200A breaker in the main panel and separate 100A fused disconnect feeding the shed. Then it is pretty much unlimited. (the 200A breaker in main panel is to prevent 200A from grid and 100A from fused disconnect together feeding 300A into main panel.)
The main house electrical panel is connected directly to the meter with no fuse disconnect. The house panel has a 200 amp breaker. This panel feeds my Shed with a 100 amp breaker. The shed has a 100 amp breaker.
 

Bob The Builder

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The main house electrical panel is connected directly to the meter with no fuse disconnect. The house panel has a 200 amp breaker. This panel feeds my Shed with a 100 amp breaker. The shed has a 100 amp breaker.
House meter connected to underground from utility co. Next is Shed sub panel.
 

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Bob The Builder

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Both panels are T&B

The system I will remove! Smart meter adds the power I made and not subtract it. Thats without going through the smart meter and being no where near house usage. Meter in picture is my meter 100 foot from my electoral company meter!
@Hedges Look at what I posted here, is this what you posted about the 120 rule, well is this why it's adding and not subtracting ?
 
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