DIY Grid Tie Solar to Lower Utility Bills

[kiwienergy]

My goal is to cut back my utilities as cheaply as possible. I am in Bay Area in California and have to deal with PGE. i am getting charged $0.32 per kwh at times
I am trying to do something similar that this youtuber did:

Monthly energy usage is low around 250kwh to 450kwh. Daily average is about 12kwh.

Example energy usage from Nov 29, 2020



I am thinking of getting one of the special grid tie inverters that don't push back to the grid.

1. Solinba 1000w Pure Sine Wave Grid Tie Power Inverter DC22-56v to AC90-130v for 24v Solar System USA Plug (or a cheaper one?)
2. 325W canadian solar panel

Thinking of maybe getting 2 of those 325W panels. Does this make sense?
I am happy if i can cut my energy bill by $10/month and drop my afternoon energy to lower levels.

Anyone with tips or anything? I think this should be fairly safe.

 

[Hedges]

You're on the right track, but why "inverters that don't push back to the grid"?
That is allowed, and permits are expedited for rooftop installations.

Two, 325W panels, 650W STC, will probably produce 500W to 550W AC. Average over the year, 2.5 kWh/day.
So 5 times that, 10 panels, would be a reasonable size grid-tie net metering system.

The downside to net metering would be if you use A/C in the summer and are a net consumer between 4:00 PM and 9:00 PM.
You'll be put on a time-of-use schedule, with rates perhaps $0.45/kWh during those hours, $0.15 Midnight to 3:00 PM, $0.30 other hours.

If you do want zero-export, there are a few systems offering that by measuring current at the utility connection with inductive pickups.

 

[kiwienergy]

Thanks for the fast reply!
I am trying to avoid the permitting process or changing my current meter... If permits involved, it will add up in costs, and with my low energy usage it will be hard to get it to back out.

If i were to get it permitted and get the NEM then i suppose I would add a larger system to take advantage of the NEM excess generation.

 

[Hedges]

PV panels can be quite cheap. Might be OK to have somewhat excess, and have inverter curtail output to avoid export.

Just glancing at what I think is the inverter you're considering, I don't see an indication it has a way to maintain zero export. Rather, is just a small inverter.

Some inverters have a current sensor to be mounted where wires come to your main breaker (if accessible), so it can make power up to what you consume, but not enough to export. I'm not sure of which brands. I think Enphase offers that, and SMA may too. But I'm not sure any are cost-effective for a small system.

If panels go on the roof, there are a bunch of new regulations, generally requiring a box on each inverter (shuts them down for fireman safety.)
Micro-inverters per panel accomplish the same thing.

 

[ArthurEld]

I am curious about using solar without dealing with permits.
Is connecting solar power to the main electrical box without a permit against the rules? I imagine it is.

But it is ok to use a hybrid inverter and wire it to plug into the wall. Then plug an air conditioner into the inverter.
You could set the inverter to use solar when available but use grid power when there's not enough solar.

There is this transfer switch too but I don't think you can save much money compared to buying a hybrid inverter.

 

[Hedges]

I am curious about using solar without dealing with permits.
Is connecting solar power to the main electrical box without a permit against the rules? I imagine it is.

But it is ok to use a hybrid inverter and wire it to plug into the wall. Then plug an air conditioner into the inverter.
You could set the inverter to use solar when available but use grid power when there's not enough solar.

There is this transfer switch too but I don't think you can save much money compared to buying a hybrid inverter.

Of course anything hardwired in to household electrical requires a permit. Anything backfeeding to the grid as well. PV panels attached to the house have potential to start a fire and can represent hazard to firemen, so even as an isolated system I think those do too.

A system with grid-tie inverter plugged into an outlet would be capable of backfeeding the grid. If more than a few amps AC, it also has the issue of potentially overloading wires - say wiring in the wall was 14 awg, breaker was 15A, and the inverter fed 10A. Downstream loads could draw 25A which would exceed safe current in the wire.

A hybrid inverter functioning as UPS with PV panels would be OK, only draws current from the outlet to power loads plugged into it. What you want is something that keeps its batteries charged, uses up to 100% of PV generation for loads, draws more power from AC as required. That could be implemented as grid-tie with zero export (in which case represents hazard for lineman if the zero export function doesn't work properly.) Or it could be an on-line UPS, always driving loads with an inverter from battery, and drawing only enough grid power to keep battery charged. Some may just be a transfer switch - run loads off battery until it gets low then switch to grid power. That would cycle the battery, OK if battery can handle enough cycles (perhaps 3500 deep cycles in 10 years.)

The transfer switch Will shows in his video simply connects certain loads to your backup AC source. Could have been a gas generator, but instead your off-grid power system consisting of battery, inverter, PV panels. That would cycle batteries. Better I think to add an AC battery charger set to a voltage slightly below what the PV SCC is set to.

Batteries are never cost effective, unless you're willing to pay more than utility rates to have power during blackouts, or you are a distance from the grid so having the utility string wires costs too much.

What you want is either grid tie with net metering, or grid-interactive with zero export. That way you use up to 100% of available PV generation to power loads and seamlessly draw any additional power required from the grid.

 

[Hedges]

Zero Export (with grid-tied inverters) is something many here could use.

I don't know who has the most cost-effective products for that. It requires measuring power at the utility connection - current and voltage, to distinguish power received from power exported by whether current is in-phase with voltage or 180 degrees out of phase. And, it requires a grid-tie inverter which can adjust output to keep power from crossing over from "import" to "export".

SMA mentions zero export, mostly in conjunction with their "Sunny Boy Storage" battery inverter

Solar Spotlight: From Net-Metering to Zero-Export With Sunny Boy Storage - Sunny. SMA Corporate Blog

The SMA Sunny Boy Storage offers an AC coupled architecture, enabling installation at any point in time. This provides greater...

www.sma-sunny.com

Also regarding commercial systems, mentioning non-US products

https://files.sma.de/downloads/ZeroRiskwithZeroExport_TI-en-11.pdf

Another thread mentions Elgris zero export:

Growatt 8000-US Grid Tie Inverter with Growatt Meter?

We use the same electric system as the US with two 110 lines and a ground/neutral. We are not allowed to sell power back to the grid without huge upfront costs and then the payback is tiny, never cost recoverable. I have a Growatt 8000-US, designed for our type system, grid tie inverter that we...

diysolarforum.com

That says, "Solar inverter independent", but it needs a way to regulate output of the inverters, or at least knock them offline.

Another thread mentions Schneider and Enphase, both needing an add-on box:

elgris ZERO EXPORT controller

Has anyone heard of this? Can it be used with an off-grid inverter and make it grid-tie?

diysolarforum.com

https://enphase.com/sites/default/files/downloads/support/Zero-Export-explained-for-DNSPs.pdf

It appears Enphase "Envoy S Metered" is the model which supports this. It would require access to the wires feeding main breaker panel, which is possible without involving the utility company only if main breaker is not built into the panel.

https://store.enphase.com/storefront/en-us/envoy-s-metered-na

 

[ArthurEld]

The inverter I linked is zero export. It does require a battery though.
I bought the 3000W version. And I'm going to have to figure out how to not overload the circuit I plug it in to.
I also bought four 100W panels to play with. It's amazing how cheap those are now. 4 for $271 delivered.

 

[Hedges]

Can that hybrid use 100% of PV and supplement with grid power?
Or does it run entirely off PV/battery until discharged, then switch to grid?

The 1 kW unit says 40A (12V PV) charging, 20A AC charging. So it can't sustain 1 kW from either PV or AC. Would have to close a relay connecting grid to load. So then the question is whether it will add PV/inverter to that (synchronized like grid tie), or just uses PV to charge battery backup. That could run past cycle life of battery quickly, if cycling several times a day.

 

[ArthurEld]

These pictures are from the manual-
There are more modes too





edit: updated manual link

 

[Ampster]

I think Enphase offers that,

Yes, as explained by others it takes the Envoy and CT clamps to do that. That adds $500 to the system cost but it is scalable. As more micro inverters are added the same Envoy can handle many more.

 

[ArthurEld]

Can that hybrid use 100% of PV and supplement with grid power?
Or does it run entirely off PV/battery until discharged, then switch to grid?

The 1 kW unit says 40A (12V PV) charging, 20A AC charging. So it can't sustain 1 kW from either PV or AC. Would have to close a relay connecting grid to load. So then the question is whether it will add PV/inverter to that (synchronized like grid tie), or just uses PV to charge battery backup. That could run past cycle life of battery quickly, if cycling several times a day.

I don't think my pictures answer your question completely. I'll keep looking. It doesn't say that I can use PV and grid without charging the batteries.
I don't plan to leave it on all the time but I would like to be able to control everything of course. I did read that it won't work without batteries but I don't know why.

 

[AZ wan]

@kiwienergy I also watched BeattheBush videos and inspire me to create my mini DIY solar panel system. What kind of grid-tied inverter did you end up with? I bought Y&H 1000w Grid tie inverter for my 880W 12V in a parallel system, yet the system only produces less than 2.0 kWh in September.

​

Amazon.com

 

[Ampster]

yet the system only produces less than 2.0 kWh in September.

Go to PV Watts to get a reasonable estimate of panel production for your location. There are a lot of variables. Are you able to measure panel production or is that number you posted inverter output?

 

[AZ wan]

Go to PV Watts to get a reasonable estimate of panel production for your location. There are a lot of variables. Are you able to measure panel production or is that number you posted inverter output?

I measure based on my Etekcity Wifi Outlet (below Amazon link for model number). Or I should you a different measurement?

Amazon.com

I put my home address with 0.880 kWh system information. It is sad my system is less than half of PV Watts assumption (December 4.48 vs 1.67 perfect Arizona sunny day with no shade).

 

[Ampster]

Or I should you a different measurement?

It is probably losses in the inverter, wiring and from the suicide plug you are using for "grid tie". The meter itself may not be calibrated for backfeed.

 

[AZ wan]

It is probably losses in the inverter, wiring and from the suicide plug you are using for "grid tie". The meter itself may not be calibrated for backfeed.

My system got inspired by this Youtuber Sean Moua along with BeattheBush . Do you have other meters recommend for the small DIY system (under 1000 W)? Once I figure out why my daily production puzzle (only produce less than 2.0 kWh in Sept.), I will go buy more panels from SanTan Solar and expand my weekend DIY project.

 

[Ampster]

I will go buy more panels from SanTan Solar and expand my weekend DIY project.

That may increase throughput to a point, but It is hard to incrementally expand a system without a long term plan. Also at some point you would be at risk of overloading the circuit serving that plug. In addition, efficiency does not scale up as you add panels. I would suggest that part of your hobby should include some tools that would increase your ability to learn from your weekend projects. Another possibility related to inverter efficiency is that your inverter may not have circuits that can harvest your solar production efficiently. A MPPT (maximum power point tracking) circuit could add efficiency to the harvesting of electricity from your panels.

 

[Hedges]

Do you have other meters recommend for the small DIY system (under 1000 W)?

Do you mean "Inverters"?
Check eBay and Craigslist for a used or surplus grid-tie high voltage string inverter. Might be 2500 to 6000W.
One with a wide range of MPPT voltage would let you start small, expand with series panels to something less than 600Voc.
That would offset your consumption, unless you expand to the point of being a net exporter and get busted by the utility.

 

[AZ wan]

Do you mean "Inverters"?
Check eBay and Craigslist for a used or surplus grid-tie high voltage string inverter. Might be 2500 to 6000W.
One with a wide range of MPPT voltage would let you start small, expand with series panels to something less than 600Voc.
That would offset your consumption, unless you expand to the point of being a net exporter and get busted by the utility.

I plan to purchase a grid-tie inverter from Amazon first then eBay. I have a Y&H 1000W Grid Tie Inverter Stackable MPPT Pure Sine Wave DC10.8-30V, but I am thinking of purchasing the bigger watt size inverter to give more rooms for expansion. Do you have any in mind for 1000W-3000W?

I don't plan to become a net exporter and pay a big fine. Too many headaches when they knock my door!

 

[Hedges]

There are some inverters which use current transformers to measure current in the grid connection, so they can regulate their output to never exceed your household current draw. That would be the ideal for zero export. I'm not sure which brands to recommend for that.

Maybe you would want solar/battery backup for some loads, like internet connection. You can get a hybrid which will do that.

What I have and recommend is SMA Sunny Boy. You can pick up used working inverters like SWR2500 (2.5 kW) or 3000US. These are string inverters; you connect enough panels in series to reach their input voltage, could be 250 to 400VDC. Several other brands do the same thing.
I trust these as quality, UL1741 listed inverters that will disconnect when the grid goes down, for safety of utility workers.

For instance:

SMA Sunny Boy Swr-2500u Grid-tie Inverter 240v for sale online | eBay

Find many great new & used options and get the best deals for SMA Sunny Boy Swr-2500u Grid-tie Inverter 240v at the best online prices at eBay! Free shipping for many products!

www.ebay.com

SMA Sunny Boy SB3800TL-US-22 Solar Inverter with DC Disconnect | eBay

Up for sale is a lightly used SMA Sunny Boy SB3800TL-US-22 solar inverter. Installed for less than a year before being swapped out to a larger inverter when the solar system was upgraded. In perfect working condition.

www.ebay.com

These are older models. Sometimes I see them for much less either on eBay or Craigslist.

The newer SMA "-40" and "-41" models have a feature that they can give you AC on a separate outlet, during power failures, without batteries. Direct from PV, while the sun shines. But they do cost more.

 

[AZ wan]

@Hedges Is SWR2500 (2.5 kW) easy to install for a DIY homeowner? Or am I better off to hire an electrician? It looks very different from the Amazon Y&H 1000W inverter I currently have. They are plug and play grid-tie inverter. Most DIY YouTube videos I watched used Sun, SolarEdge, Eco worthy Grid Tie Inverter or alike.

What kind of thickness AWG wire do you recommend if I choose SWR2500 in series? 10 AWG, 8 AWG or thicker? For the panels, I plan to purchase used panels from SanTan Solar (https://store.santansolar.com/product-category/solar-panels/)
Here is their spec. Any thought or I should invest in the new panel instead. SanTan also sells new panels and some of them are on sale.

SanTan Solar T Series 250W, $50 each​

Rated Power: 250W
Open circuit voltage (VOC): 37.6 V
Max power voltage (VMP): 30.3 V
Short circuit current (ISC): 8.85 A
Max power current: 8.27 A
Power Tolerance 0/+3%
Maximum system voltage: 600V (UL)
Fuse Rating: 15 A
IP65 Junction Box w/MC4 Compatible Connectors
Frame: Anodized aluminium alloy
Weight: 41 lbs
Dimensions: 1650 × 992 × 35mm (64.95 × 39.05 × 1.37 inches)

SanTan Solar T Series 250W Snail Trails, $45 each​

Rated Power: 250W
Open circuit voltage (VOC): 37.6 V
Max power voltage (VMP): 30.3 V
Short circuit current (ISC): 8.85 A
Max power current: 8.27 A
Power Tolerance 0/+3%
Maximum system voltage: 600V (UL)
Fuse Rating: 15 A
IP65 Junction Box w/MC4 Compatible Connectors
Frame: Anodized aluminium alloy
Weight: 41 lbs
Dimensions: 1650 × 992 × 35mm (64.95 × 39.05 × 1.37 inches)

 

[Hedges]

It is pretty easy, because the dangerous high voltage DC from panels, which can't be turned off, uses MC4 connectors.
By putting the cover on before connecting panels (and waiting several minutes after disconnecting before removing cover), the DC voltage can't be touched.
Turning off main breaker in panel similarly removes all dangerous AC voltages (except the screw terminals on the main breaker) while you work in the box.

These things are supposed to be hard wired, not plugged in, but I've done that with a 240V outlet for testing.

I used 12 awg on both AC and DC side.
AC goes to a 15A 2-pole breaker.
DC side ought to go through a 600VDC rated switch (somewhat hard to come by), but if the MC connectors were mated after sundown, that would avoid arcing as it chargers the capacitor.

Here's the switch I used, has 3 poles so supports 3 inverters

Square D 30 Amp Heavy Duty Safety Switch Model HU361RB / 600VAC | eBay

Find many great new & used options and get the best deals for Square D 30 Amp Heavy Duty Safety Switch Model HU361RB / 600VAC at the best online prices at eBay! Free shipping for many products!

www.ebay.com

Those PV panels would work, although better to get something with UL stickers still present in case it ever needs to be approved.
Maybe the "snail trails" are OK, but I ordered others with no defects.
I wouldn't buy any with cracked backsheets for high voltage series strings.

I'm not familiar with "Hansol" but these say new, manufacturer's warranty

Hansol 355W - SanTan Solar Store

Check out our brand new Hansol 355W 72 cell monocrystalline panels! They come with the manufacturers warranty! Only $0.41/watt!

store.santansolar.com

• Open circuit voltage (VOC): 47.8 V

You could connect 10 to 13 "Santan 250W" panels with specs as shown. 13 x 37.6 = 489 Voc. 1.2 x that for cold, still below 600V limit.
Or 7 to 10 "Hansol 355W"

For DC wiring, get a long MC cable (12 awg is good) and cut in half. With just one panel connected to the two cut pieces of cable (safe low voltage), check polarity and mark which is positive so it connects to inverter correctly.

A grounding lug should be used to connect a wire from frames of all panels back to ground in the inverter, which connects to ground of breaker panel. That way if a panel has electrical leakage (e.g. if wet and has crack or other fault) the frames are grounded, won't have high voltage.

One Burndy Tin Plated Copper Lay-in Lug weeb CL50-1TN | eBay

The Burndy Lay-In QIKLUG™ is manufactured from high strength pure electrolytic copper to ensure maximum strength and conductivity. The open-faced design allows for fast lay-in of the conductor without the need for cutting or breaking.

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Wiley Electronics WEEB-LUG-6.7 Lay-In Lug and Hardware | eBay

Wiley Electronics WEEB-LUG-6.7 Lay-In Lug and Hardware. Condition is "New". Shipped with USPS First Class.

www.ebay.com

You can add lightning protection devices on AC side, possibly DC side. I think the ones I used for 17 years were actually useless (some are more snake oil while others are legitimate.) Whether you need them depends on whether you get a lot of lightning strikes in your area (like Florida)

 

[iamrich]

I plan to purchase used panels from SanTan Solar (https://store.santansolar.com/product-category/solar-panels/)

SanTan Solar T Series 250W Snail Trails, $45 each​

Rated Power: 250W
Open circuit voltage (VOC): 37.6 V
Max power voltage (VMP): 30.3 V
Short circuit current (ISC): 8.85 A
Max power current: 8.27 A
Power Tolerance 0/+3%
Maximum system voltage: 600V (UL)
Fuse Rating: 15 A
IP65 Junction Box w/MC4 Compatible Connectors
Frame: Anodized aluminum alloy
Weight: 41 lbs
Dimensions: 1650 × 992 × 35mm (64.95 × 39.05 × 1.37 inches)

I got a pallet today (12 total). I didn't get a chance to test them but they look to be in good condition. $49 each (after figuring in shipping). I don't think you can go wrong with these panels (unless you are short on space/real estate).

 

[AZ wan]

I got a pallet today (12 total). I didn't get a chance to test them but they look to be in good condition. $49 each (after figuring in shipping). I don't think you can go wrong with these panels (unless you are short on space/real estate).

I glad you purchased from San Tan Solar. I don't know them until I searched "used solar panel" from YouTube. SanTan Solar has a 10% off on all solar panels promotion until 1/8/21! I "like" their Facebook page and will get notification whenever they have a promotion. Based on the YouTube videos I watched, all the users who purchased their used panels are satisfied. If I have a large pick-up, I will drive their warehouse, pick up the panels, and save some shipping cost.


@Hedges Thank you for your detailed information and ground lug! Because I have a solar system agreement already with my utility company, they limit my grid-tie expansion. I may only increase my system's capacity by a total of 10% or 1 kW, whichever is greater. If I bleach the contact, I will pay an expensive service fee for using their services.

I am unsure I can go to a battery bank route to bypass the 10% system capacity limit. But the initial investment will be out of my budget. Buy 10 used panels (250 x 10 =2500 W) will be around $500. Four 12V/200Ah battery will be around $1400 easily at Wal Mart along with controllers, breakers, wires, and wooden storage cases. Setting up an off-grid system battery bank is confuse me. The battery may only have ten years lifespan.

Right now, I am waiting for my tax refund and Trump's $1400 check. Then I decide my solar project. I may keep saving money and invest the powerwall instead. My solar panel installer Solar Topps sells Encharge 10 10.5 kWh battery wall for $10,286, Panasonic EVAC-105-4 11.4 kWh $9,546 (https://www.solartopps.com/residential-plan/) I heard Telsa Powerwall is great with many app features. The initial cost will be roughly between $9,600 and $15,600 for a full system installation.