System 2: Permitted Standalone (3.2kW)

What you’ll build

A permitted, inspected, code-compliant standalone solar system. The real thing. Eight 400-watt panels on your shed or garage roof, wired in a single series string, feeding an off-grid inverter/charger that charges a 5kWh LiFePO4 battery and outputs 120V AC to a single duplex outlet. No grid connection. No house connection. Standalone.

This is the minimum viable system that goes through the full permit and inspection process and comes out the other side signed off. One permit. Two inspections. Done. Nobody comes back.

System specs:

8 × 400W monocrystalline panels (3,200W array)
Single series string
Off-grid inverter/charger with MPPT
5kWh LiFePO4 battery (48V, 100Ah)
Single 120V GFCI duplex outlet
Full grounding electrode system
Not connected to the grid or any other building

If you built System 1 (200W Safe Harbor), you already know how panels, charge controllers, and batteries work. System 2 is the same idea at a real scale, with permits, inspections, AC output, code-compliant grounding, and a system that can run actual loads. The trade-off for that paperwork is a system that’s legally bulletproof and genuinely useful.

What you can power

With 3,200 watts of panels and Oregon’s 3–4 peak sun hours, you’re generating roughly 7.7–10.2 kWh per day (after an 80% system derate for real-world conditions: temperature, wiring losses, inverter efficiency). The 5kWh battery stores a meaningful evening load.

Through the single 120V outlet, you can run:

Power tools - circular saw, drill press, grinder, compressor (watch the surge draw)
A mini-fridge or chest freezer - keep drinks cold in the workshop or store food in the garage
LED work lights - light up the whole space, all evening, on a fraction of your daily harvest
Phone, laptop, and battery chargers - everything charges from the outlet
A small space heater - with caveats: a 1,500W heater will draw heavily from the battery and can drain 5kWh in about 3 hours. Use it for taking the edge off, not heating all day.
Radio, speakers, small TV - background entertainment while you work

One outlet is intentional. It’s the minimum endpoint that makes the system complete for inspection. The inspector sees a finished circuit from generation through storage, conversion, disconnection, and utilization. Nothing is dangling, nothing is “to be continued.” If you want more outlets or lighting later, run additional branch circuits from a small subpanel. That’s all under the same permit framework.

The permit process

This isn’t a legal minefield. It’s a bureaucratic process. Walk in, fill out the form, pay the fee, do good work, call for inspections.

Who can do this

Under ORS 479.540, you must be:

The owner of the property
The occupant of the property (you live there)
The property cannot be intended for sale, lease, rent, or exchange in the near future
You perform the work yourself
The work must comply with all applicable codes

You don’t need an electrical license. The homeowner exemption means you can do the work yourself. It doesn’t mean you can skip the rules.

Where to go

Portland: Bureau of Development Services (BDS), portland.gov/bds. Residential electrical permits can be applied for online or in person. BDS offers 15-minute appointments for permit questions.

Outside Portland: Contact your local building department (the Authority Having Jurisdiction, or AHJ). The process is similar everywhere in Oregon, but fees and specific procedures vary.

What to bring

Completed electrical permit application
Basic site plan showing the structure’s location on your property
Simple line diagram of the system: Panels → DC Disconnect → Inverter → Battery → AC Disconnect → GFCI Outlet
Equipment specification sheets for panels, inverter, and battery, showing listed/certified status (UL markings)
You sign the permit as the homeowner

What it costs

Permit fees vary by jurisdiction and scope of work, typically a few hundred dollars for a residential electrical permit. Contact your local building department for the current fee schedule.

The 180-day clock

Per OAR 918-309-0000, your permit expires if work is not started within 180 days of issuance, or if work is suspended or abandoned for 180 days after starting. Each passed inspection resets the clock.

Inspections

Your permit entitles you to two inspections:

Rough-in inspection - wiring installed but not concealed. The inspector checks conductor routing, sizing, box fill, grounding path, and general workmanship. Call when your wiring is in place and visible.
Final inspection - everything installed, connected, labeled, and operational. The inspector checks the full checklist: disconnects, labeling, grounding continuity, listed equipment, overcurrent protection, GFCI, the works.

Have the permit posted on site, equipment spec sheets available, and your line diagram visible for both inspections.

System design

Before you buy anything, understand why each component was chosen and how they work together. This section is the engineering rationale. The bill of materials comes next.

Panels and string configuration

8 × 400W monocrystalline panels, wired in series (positive of one panel to negative of the next).

400W is the sweet spot for residential panels: good output per panel, manageable physical size (~6.8’ × 3.4’, about 22 square feet, 45–55 lbs), widely available, and priced competitively. Unless you have a specific reason to go smaller or larger, 400W panels are a solid default.

Typical specs per panel (varies by manufacturer):

Spec	Value
Open-circuit voltage (Voc)	~41V
Short-circuit current (Isc)	~13A
Maximum power voltage (Vmp)	~34V
Maximum power current (Imp)	~11.8A

Listing requirement: Panels must be certified to UL 61730 (current standard) or UL 1703 (legacy standard). Every panel from a reputable manufacturer (Canadian Solar, REC, QCells, LONGi, JA Solar, Trina) meets this. It’s printed on the panel label.

String electrical characteristics (8 panels in series):

Spec	Calculation	Result
String Voc	8 × 41V	328V DC
String Isc	same as one panel	13A
String Vmp	8 × 34V	272V DC
String Imp	same as one panel	11.8A

Temperature correction (NEC 690.7): Panels produce their highest voltage in cold weather. For Portland, the lowest expected temperature is approximately -15°C (5°F). Using NEC Table 690.7(A) correction factor of 1.14 for crystalline silicon:

Temperature-corrected maximum Voc: 328V × 1.14 = 374V DC

This is the number that drives everything. All DC equipment, disconnects, and wire insulation must be rated for at least 374V DC. Use 600V DC rated components. They’re standard and provide margin.

Why single string: One string means one set of wires from roof to inverter. No combiner box, no parallel string balancing, no additional overcurrent protection for backfeed. Simple and clean. The current stays at 13A (series wiring adds voltage, not current), which keeps conductor sizing manageable.

Inverter

You need an off-grid inverter/charger - a single unit that accepts DC input from the solar array, charges a battery, and outputs 120V AC. This replaces the simple charge controller from System 1 with a device that does everything.

Key specs to match:

Requirement	This System	What to Look For
MPPT voltage window	272V–374V DC	Must accept this range, check min and max
PV input power	3,200W	MPPT rated for at least 3,200W input
AC output	120V, single phase	3,000–3,500W continuous minimum
Surge rating	2× continuous or better	For motor startup (tools, fridge compressor)
Listing	UL 1741	Non-negotiable for inspection

Representative products (verify current availability and listing):

EG4 6000XP - popular in the DIY community, UL 1741 listed, MPPT 120–500V DC
Victron MultiPlus series - well-regarded off-grid, UL listed
Sol-Ark - hybrid with off-grid capability, UL listed
Growatt SPF series - verify UL 1741 listing on the specific model

Why 120V, not 240V: A single 120V outlet is the simplest endpoint. It covers power tools, a fridge, lights, chargers, everything you’d reasonably run in a workshop. 240V adds wiring complexity, a different transfer configuration, and cost. If you don’t have a specific 240V load, start with 120V.

Battery

5kWh LiFePO4 - a single 48V, 100Ah server rack battery.

Listing requirement: The battery must be listed. For lithium-ion, the relevant standards are UL 9540 (Energy Storage Systems), UL 9540A (Thermal Runaway Fire Propagation), or UL 1973 (Batteries for Stationary Applications). Most reputable LiFePO4 manufacturers meet these. Check the label or spec sheet.

Why LiFePO4:

No hydrogen gas, so minimal ventilation requirements (unlike flooded lead-acid)
Built-in Battery Management System (BMS) handles cell balancing, over/under voltage protection, temperature protection
Long cycle life: 3,000–6,000+ cycles (vs. 300–500 for lead-acid)
Most thermally stable lithium chemistry, the safest option

Why 5kWh: It provides meaningful overnight storage. At 85% usable depth of discharge, you get ~4.25kWh of usable energy, enough to run LED lights, a fridge, and some electronics for 8–10 hours after dark. It’s also the simplest configuration: one battery unit, one set of connections.

Representative products (verify listing before purchasing):

SOK 48V 100Ah, UL listed
EG4 LL series, UL listed
Victron Lithium Smart series, UL listed

Expansion: This is the easiest part of the system to expand later. A second rack battery wired in parallel doubles your storage without changing anything else. Make sure your battery rack has room for growth.

Battery communication: Modern batteries communicate with the inverter digitally over CAN bus or RS485. This lets the inverter manage charging precisely: right voltage, right current, right cutoffs. Confirm compatibility between your specific battery and inverter models before purchasing. The forums are the best resource for confirming which combinations actually work well together.

Approximate cost: $1,500–2,500 for a 5kWh listed LiFePO4 battery.

Grounding and bonding

There are two separate grounding concepts, and both are required.

Equipment grounding (bonding)

Purpose: Ensure every metallic component that could become energized during a fault has a path to ground, so fault current trips an overcurrent device before someone touches it.

What gets bonded:

Every panel frame
All racking / mounting hardware
All metallic junction boxes
Inverter enclosure
Battery enclosure (if metallic)
All metallic conduit
DC and AC disconnect enclosures

How to bond panel frames:

Install a listed PV grounding lug (UL 2703) at each panel frame. Products like WEEB, IronRidge, Burndy, or Ilsco grounding lugs work well. These have serrated/toothed contact surfaces that bite through the anodized coating on aluminum panel frames. Cost: $2–5 each.
Run a continuous bare or green copper Equipment Grounding Conductor (EGC) from lug to lug, daisy-chaining through each panel.
Continue the EGC to the inverter grounding terminal and then to the grounding electrode.

EGC sizing: 10 AWG copper minimum (per NEC 690.45 / Table 250.122).

Grounding electrode system

Purpose: Connect the electrical system to the earth to stabilize voltage and provide a reference.

What you need:

Two ground rods - 8 feet long each, copper-clad steel, driven vertically, at least 6 feet apart. Most people drive two and skip the resistance testing.
Grounding Electrode Conductor (GEC) - connects the system grounding point to the ground rods. 6 AWG bare copper (minimum 8 AWG per NEC 250.66, but 6 AWG is recommended and common).
Listed clamps - acorn clamps or listed ground rod clamps at each rod connection. Not hose clamps. Not wire wraps.
Physical protection - per NEC 250.64(B), the GEC must be protected from physical damage where exposed. If it runs down an exterior wall, protect it with conduit.

Standalone system grounding

Since this system has no electrical connection to the house or any other structure, the grounding electrode system is self-contained. You do not need to bond back to the house’s grounding electrode system. The shed has its own ground rods, its own GEC, and its own grounding path.

Bill of materials

Everything you need to order, organized by subsystem. Confirm UL listing on every major component before purchasing. It’s on the label or spec sheet.

Array

Item	Specs	Approx. Cost
400W Monocrystalline Panels (×8)	Voc ~41V, Isc ~13A, UL 61730. Canadian Solar, QCells, LONGi, JA Solar, Trina.	$800–1,200
Z-Bracket Panel Mounts (sets for 8 panels)	Universal fit, aluminum. Or rail-based racking.	$120–200
PV Grounding Lugs (×8)	UL 2703 listed, serrated contact. WEEB, IronRidge, or Ilsco.	$16–40

Inverter and battery

Item	Specs	Approx. Cost
Off-Grid Inverter/Charger	MPPT 120–500V DC, 3,000W+ continuous, 120V AC output, UL 1741. EG4 6000XP, Victron MultiPlus, Sol-Ark, Growatt SPF.	$1,200–2,500
48V 100Ah LiFePO4 Battery	5kWh, server rack, built-in BMS, UL 9540/1973. SOK, EG4 LL, Victron.	$1,500–2,500

DC wiring

Item	Specs	Approx. Cost
10 AWG PV Wire (red + black, 100ft ea.)	USE-2 / PV Wire, UV-rated, 600V, for exterior DC runs	$60–100
600V DC Disconnect Switch (30A)	DC-rated, NEMA 3R, listed. Array-to-inverter isolation.	$40–80
DC Battery Fuse/Breaker	DC-rated, sized per battery and conductor specs	$20–40
EMT Conduit (3/4”, 10ft sticks ×2+)	For exterior wire runs, physical protection	$15–30
Junction Boxes, Fittings, Connectors	Listed, weatherproof for exterior transitions	$20–40

AC wiring

Item	Specs	Approx. Cost
12 AWG NM-B (Romex, 25ft)	For 20A AC branch circuit, interior	$15–25
120V AC Disconnect / Breaker (20A)	Standard AC disconnect or breaker	$15–30
20A GFCI Duplex Outlet (NEMA 5-20R)	GFCI receptacle, required per NEC 210.8(A)	$15–25
Electrical Boxes + Cover Plates	Listed junction boxes, outlet box, cover plates	$10–20

Grounding

Item	Specs	Approx. Cost
Ground Rods (8ft copper-clad steel, ×2)	Driven 8ft, at least 6ft apart	$20–30
Ground Rod Clamps (acorn clamps, ×2)	Listed ground rod clamps	$8–12
6 AWG Bare Copper Wire (25ft)	Grounding electrode conductor (GEC)	$25–40
10 AWG Green/Bare Copper Wire (50ft)	Equipment grounding conductor (EGC)	$25–40

Labels

Item	Specs	Approx. Cost
PV Warning Labels (pre-made set)	“SOLAR PV SYSTEM DISCONNECT”, “PHOTOVOLTAIC POWER SOURCE”, shock hazard warnings	$15–30
Label Maker (Brother P-Touch or similar)	For custom labels: voltage, current, chemistry, power source directory	$25–40

Total estimated cost

Category	Range
Array (panels + mounting + grounding lugs)	$936–1,440
Inverter + Battery	$2,700–5,000
DC Wiring	$155–290
AC Wiring	$55–100
Grounding	$78–122
Labels	$40–70
Permit fees	$100–300
Total	$4,064–7,322

The wide range reflects component quality tiers. The inverter and battery are the biggest cost drivers. Panels have come down dramatically and are no longer the expensive part of the system.

Buying advice:

Order all 8 panels at once. Shipping panels is expensive. Adding panels to an initial order is much cheaper than ordering separately later. Get them from the same manufacturer, same model, same batch if possible.
Confirm UL listing on every major component before purchasing. Check the label or spec sheet, not the Amazon listing or marketing copy.
Research inverter-battery compatibility on the forums before buying. “Compatible” means they speak the same digital language (CAN bus / RS485), not just that the voltages match.
Buy extra wire and fuses. You’ll use them. A spare roll of PV wire and a few extra fuses cost almost nothing and save a trip to the store mid-build.
Don’t cheap out on grounding lugs and clamps. These are $2–5 each and they’re what stands between a fault and a fire. Use listed components.

Wiring topology

Here’s the full connection map from panels to outlet, with every component in the chain:

Panels (8, series) → PV Wire (10 AWG) → DC Disconnect (600V DC, 30A) → Inverter MPPT Input → Inverter Battery Port → Battery OCPD (DC fuse/breaker) → Battery (48V, 5kWh) → Inverter AC Output → AC Disconnect (120V, 20A) → GFCI Duplex Outlet (NEMA 5-20R)

Grounding path (parallel to the above): Panel frames → Grounding Lugs → EGC (10 AWG) → Inverter Ground Terminal → GEC (6 AWG) → Ground Rods (×2)

A visual wiring diagram is coming soon.

DC source circuit (panels to inverter)

Conductor sizing (NEC 690.8):

Maximum circuit current = Isc × 1.25 = 13A × 1.25 = 16.25A
Conductor ampacity ≥ 16.25A × 1.25 (continuous load factor) = 20.3A
10 AWG copper (rated 30A at 90°C) satisfies this with margin

Wire type:

Exterior / roof runs: PV Wire or USE-2. UV-resistant, wet-rated, 90°C. PV Wire is preferred (specifically designed for this, comes in red/black).
Interior (inside the shed): Transition to THWN-2 in conduit at a junction box where conductors enter the building. Or continue PV Wire in conduit, either is acceptable.

Panel interconnections: Panels connect to each other via factory-installed MC4 connectors, which are listed, weatherproof, and designed for the purpose. At the end of the string, one MC4+ and one MC4− connect to your PV wire run to the inverter. Transition from MC4 to hardwired conductors at a weatherproof junction box, or run MC4-terminated PV wire directly to the inverter if it accepts MC4 inputs.

Conduit: Where conductors run exposed on the exterior or through accessible areas, protect them with EMT (Electrical Metallic Tubing) or Schedule 40 PVC. EMT provides physical protection and can serve as an equipment grounding path.

DC disconnect

NEC 690.13 requires a means to disconnect the PV array from all wiring.

DC voltage rating: ≥ 374V DC (temperature-corrected Voc). Use a 600V DC rated switch.
Current rating: ≥ 125% of Isc = 16.25A. A 20A or 30A rated switch.
Location: Readily accessible, between array output and inverter DC input
Labeled (see Labeling section)
Must be a listed device

Battery circuit

DC-rated fuse or breaker between battery and inverter
Sized per conductor ampacity and battery short-circuit current capability
Many inverter-chargers have an integrated battery disconnect. Verify with the inspector whether this satisfies the requirement.

AC branch circuit (inverter to outlet)

12 AWG NM-B (Romex) for a 20A circuit
Stapled per NEC: within 12 inches of each box, every 4.5 feet along the run
AC disconnect between inverter output and the outlet circuit, 120V, 20A rated
GFCI protection on the outlet. NEC 210.8(A) requires it for garages and accessory buildings. Install a GFCI receptacle. This is a common inspection catch.

Labeling

Labeling is where DIY systems most frequently fail inspection. It’s easy, it’s cheap, and it’s required.

Required labels

At the DC disconnect:

“SOLAR PV SYSTEM DISCONNECT”
Maximum DC voltage: 374V DC
Maximum DC current: 13A

At the AC disconnect:

“SOLAR PV AC DISCONNECT”
Rated voltage: 120V AC

On conduits / raceways carrying PV circuits:

“SOLAR PV CIRCUIT” or “PHOTOVOLTAIC POWER SOURCE”
At every accessible point, junction box, and where the conduit enters the building

At the inverter:

Manufacturer’s listing label visible and intact

At the battery / energy storage system:

“ENERGY STORAGE SYSTEM”
Voltage (e.g., 48V DC)
Battery chemistry: “LITHIUM IRON PHOSPHATE - LiFePO4”

Power source directory (NEC 710.10):

A permanent plaque or directory at the main disconnect location identifying:
- Type of power source: Solar PV
- Location of each disconnect
- Operating voltage

Warning labels at accessible energized points:

“WARNING: ELECTRIC SHOCK HAZARD - DO NOT TOUCH TERMINALS. TERMINALS ON BOTH LINE AND LOAD SIDES MAY BE ENERGIZED IN THE OPEN POSITION.”
At the array (if accessible): “WARNING: SOLAR PV - ENERGIZED IN DAYLIGHT”

Labels must be durable, weather-resistant (for exterior use), UV-resistant, and legible per NEC 110.21(B).

Step-by-step build

1. Prep your workspace

Post your line diagram on the wall. Lay out all tools and materials. Stage everything you can on the ground: brackets on panels, connectors on wire tails, hardware sorted and bagged. Check the weather - don’t start a roof project before rain. Have your buddy lined up for panel day.

2. Pull your permit

Go to BDS (or your local AHJ) with your completed application, site plan, line diagram, and equipment spec sheets. Pay the fee. Post the permit on site where the inspector can see it.

3. Mount the panels

Eight panels on the roof of your detached structure. Pre-attach Z-brackets or rail mounts on the ground. It’s easier than doing it on the roof. Two-person job for carrying panels up and positioning them. Account for gaps between panels (1–2 inches for mounting hardware) and clearance from roof edges.

Tilt angle: the ideal year-round angle for Portland’s latitude is roughly 35–45 degrees. If your roof is close to this range (most are), it works without adjustment. Don’t overthink tilt. Getting panels up and facing generally south matters far more than the perfect angle.

4. Install grounding lugs on every panel frame

A listed PV grounding lug (UL 2703) at each panel. These bite through the anodized aluminum coating to make solid electrical contact. Run the continuous Equipment Grounding Conductor (10 AWG bare or green copper) from lug to lug, daisy-chaining through all eight panels.

5. Run PV wire from array to equipment location

Pull your 10 AWG PV wire (red and black) through EMT conduit from the panel array to where the inverter will live inside the shed. Leave service loops at both ends, extra slack so you can make connections without pulling wire tight. Transition to interior wiring method at a junction box where the conductors enter the building envelope.

6. Drive ground rods

Two 8-foot copper-clad steel rods, driven vertically, at least 6 feet apart. Use listed acorn clamps at each rod. Run 6 AWG bare copper GEC from the system grounding point to the rods. Protect the GEC from physical damage where it’s exposed on an exterior wall with conduit or routing behind a protected surface.

7. Install the inverter and battery

Mount the inverter on the wall inside the shed with ventilation clearance per manufacturer specs. Set up the battery on a rack or shelf, secured against tipping. Both need to be accessible for inspection and maintenance. Bond the inverter enclosure and battery enclosure (if metallic) to the equipment grounding system.

8. Install the DC disconnect

Between the array output and the inverter DC input. 600V DC rated, 20A or 30A. Readily accessible location. Label it now.

9. Wire the DC side

Connect the PV wire from the panel array through the DC disconnect to the inverter’s MPPT input. Leave the DC disconnect in the OFF position. Don’t energize yet. Verify polarity at every connection with your multimeter - reversing polarity on a DC input can damage the inverter permanently.

10. Wire the battery

Connect the battery to the inverter’s battery port through the DC-rated fuse or breaker. Don’t connect the battery yet - leave the battery breaker open until you’re ready to commission.

11. Wire the AC side

Inverter AC output → AC disconnect → GFCI duplex outlet. Use 12 AWG NM-B, stapled per NEC (within 12” of boxes, every 4.5’ along the run). Install the GFCI receptacle in a proper electrical box with a cover plate. Wire hot, neutral, and ground correctly.

12. Install all labels

Every label listed in the Labeling section above. DC disconnect, AC disconnect, conduits, battery, power source directory, warning labels. Do this now, before you call for any inspection. Use your label maker or pre-made PV labels.

13. Call for rough-in inspection

Your wiring is installed and visible, not concealed behind anything. Have the permit posted, equipment spec sheets on hand, and your line diagram visible. The inspector checks conductor routing, sizing, box fill, grounding path, and general workmanship.

14. After rough-in passes: energize and test

Bring the system up methodically. Don’t flip everything on at once.

DC disconnect ON - check string voltage at the inverter’s MPPT input with your multimeter. It should be near your expected string Voc (adjusted for current temperature and sun conditions). If it’s wildly off, stop and figure out why.
Connect the battery - close the battery breaker/fuse. Verify the inverter sees the battery: state of charge should display, communication status should show connected. If the inverter and battery aren’t talking, don’t proceed.
Turn on AC output - check voltage at the GFCI outlet with your multimeter. You should see ~120V AC.
Test the GFCI - press the test button. The outlet should kill power. Press reset. Power returns. This takes two seconds and confirms a critical safety device.
Plug in a load - a lamp, a phone charger, anything. Confirm it works.

15. Call for final inspection

Everything is complete, labeled, and operational. The inspector checks the full checklist below. Have your permit posted, spec sheets available, and line diagram visible. Walk the inspector through the system if they want. Most appreciate a homeowner who understands their own installation.

Inspection checklist

Self-audit before calling for inspection. Go through every item. The inspector will.

Documentation

Permit posted on site
Equipment spec sheets available for all major components
Line diagram of the system available
Panel listing (UL 61730 / UL 1703), visible on panel label
Inverter listing (UL 1741), visible on unit
Battery listing (UL 9540 / UL 1973), visible on unit or spec sheet

Array

Panels securely mounted
Equipment grounding lug at each panel, listed (UL 2703), biting through anodization
Equipment grounding conductor continuous through all panels
MC4 connections seated and locked (tug-test every one)
PV wire / USE-2 used for exterior runs
Conductors secured and protected from physical damage

Disconnects

DC disconnect installed, accessible, properly rated (600V DC, 20–30A)
AC disconnect installed, accessible, properly rated (120V, 20A)
Both disconnects operational (open/close)

Wiring

Conductor sizing correct (10 AWG minimum DC source, 12 AWG for 20A AC branch)
Proper wire types (PV Wire exterior, NM-B interior, THWN-2 in conduit)
All connections in listed boxes or enclosures, no open splices
Conduit fill within limits
NM-B stapled properly (within 12” of boxes, every 4.5’)

Grounding

EGC continuous from array through all components to grounding electrode
Ground rod(s) driven 8 feet, with listed clamp connection
GEC properly sized (6 AWG recommended)
GEC protected from physical damage where exposed
Inverter enclosure bonded
All metallic enclosures bonded

Overcurrent protection

DC fuse or breaker for source circuit
Battery circuit overcurrent protection installed
AC branch circuit breaker matches wire gauge (20A for 12 AWG)

Outlet

GFCI protection (GFCI receptacle or GFCI breaker)
Proper box, cover plate, and mounting
Correct wiring (hot, neutral, ground)

Labels

DC disconnect labeled with voltage and current
AC disconnect labeled
PV circuit conduits/raceways labeled
Battery/ESS labeled with voltage and chemistry
Power source directory posted at main disconnect
Warning labels at accessible energized points

Safety

This system stores and moves serious energy: 374V DC from the array and 48V from a battery that can deliver hundreds of amps into a fault. Respect it.

Panels are always live in daylight. There is no off switch on a solar panel. Cover them with opaque material while working on wiring connections. Treat panel-side wires as energized whenever the sun is up.
Fuse and protect every circuit. DC source circuit, battery circuit, AC branch circuit - overcurrent protection at every junction. Oversized protection doesn’t protect. Match fuse/breaker ratings to conductor ampacity and component specs.
Use listed, certified components. UL markings are not optional. They’re what the inspector checks, and they’re what your insurance requires. The cost difference between listed and unlisted components is negligible. The risk difference is not.
Torque all connections to spec. Battery terminals, wire lugs, grounding connections all have specified torque values. A loose connection creates resistance. Resistance creates heat. Heat creates fire. Use a torque wrench or torque screwdriver.
UV-rated wire for all exterior runs. Standard wire degrades in sunlight. PV Wire and USE-2 are designed for this environment.
Mount the inverter and battery indoors with adequate ventilation per manufacturer specs. Protected from weather, accessible for maintenance and inspection.
Tug-test every MC4 connection. A click doesn’t always mean fully seated. A loose MC4 creates a resistance point and a potential fire hazard.
If anything feels wrong, stop. Smells hot, sparks, readings that don’t match, something that doesn’t look right - disconnect and figure it out before proceeding. The Johnny Solarseed consult page exists for exactly this.

What’s next

You have a permitted, inspected, signed-off standalone solar system. That’s a real thing. It’s legal, it’s safe, and it’s yours.

Expansion options:

More battery. Add another 48V rack battery in parallel. Doubles your overnight storage without changing anything else. Same permit framework.
More outlets or a subpanel. Run additional 120V branch circuits from the inverter through a small subpanel. More utilization points, same system.
Ground mount. If you have another structure or open yard space, a ground-mounted array is easier to install, easier to maintain, and still exempt from rapid shutdown.
Monitoring. Most modern inverters have apps that show real-time production, battery state of charge, and consumption. Set it up and learn your system’s patterns: when it produces, when it draws down, how weather affects output.

This system is the foundation for everything bigger. You’ve done the permit process, you understand the code, and you have a relationship with your local building department. Adding capacity later is iteration, not starting over.

If you haven’t built System 1 (200W Safe Harbor) yet, consider starting there. It’s a one-afternoon project that teaches you the fundamentals with zero permits and zero risk. The learning curve is behind you before you tackle this build.