System 2: Permitted Standalone (3.2kW)

A full code-compliant standalone solar system with battery storage and 120V AC output. This is a capital improvement — a real asset with real inspections that powers real loads.

What You’ll Build

Spec	Value
Array	8 × 400W panels (3,200W STC)
Inverter	Off-grid inverter/charger
Battery	5kWh LiFePO4
Output	120V / 20A GFCI-protected
Daily production	~12–16 kWh (location-dependent)
Permit required	Yes — homeowner electrical permit
Inspections	Rough-in + final

What You Can Power

This system produces enough energy to run significant loads through a dedicated circuit:

Refrigerator/freezer (24/7 operation)
Window A/C unit (during peak sun hours)
Power tools in a shop or garage
Well pump (intermittent loads)
EV trickle charging (Level 1)

The 5kWh battery bank carries overnight loads or handles cloud cover. Think of this as a dedicated power station on your property — separate from the grid, separate from your utility bill.

The Permit Process

Homeowner Electrical Permits

In most states, homeowners can pull their own electrical permits for work on property they own and occupy. This is a fundamental property right. You don’t need to be a licensed electrician to wire your own system — you just need to meet code.

What to Expect

Application — Fill out the permit application at your local building department. Describe the project as “standalone solar PV system with battery storage, not connected to building electrical system.” Include your site plan showing panel location.
Plan review — The building department reviews your plans. For a standalone system, this is typically straightforward. Include your wiring diagram, equipment spec sheets, and site plan.
Rough-in inspection — Inspector verifies mounting, grounding, conduit runs, and wire sizing before you close up any junction boxes. Schedule this after mechanical installation is complete.
Final inspection — Inspector verifies labeling, overcurrent protection, grounding/bonding, and operational safety. System must be energized for this inspection.

Typical Timeline

Permit application to approval: 1–2 weeks
Build time: 2–3 weekends
Inspections: Schedule within a few days of request
Total: 3–6 weeks

System Design

Panels

Parameter	Value
Module	400W mono-PERC (any Tier 1)
Quantity	8
V_oc (typical)	~41V
I_sc (typical)	~13A
String configuration	2 strings of 4 panels
V_oc per string	~164V

String voltage calculation (NEC 690.7):

The inverter’s MPPT input range determines your string length. With 4 panels per string:

V_oc × 4 = ~164V (within typical 150–500V input range)
Verify against your specific inverter’s MPPT voltage window
Apply temperature correction factor per NEC 690.7 for your climate zone (cold temperatures increase voltage)

Inverter

Parameter	Value
Type	Off-grid inverter/charger
Output	120V / 60Hz split-phase capable
Continuous power	3,000W minimum
Surge rating	6,000W minimum
MPPT inputs	2 (one per string)
Battery voltage	48V nominal
Transfer switch	Built-in (if using backup grid)

The off-grid inverter/charger is the brain of your system. It handles:

MPPT — Maximum Power Point Tracking to optimize panel output
Battery charging — Manages charge profiles for your LiFePO4 bank
AC conversion — Produces clean 120V/60Hz sine wave output
Load management — Handles surge loads and overload protection

Recommended units: Look for UL 1741 listed inverter/chargers from established manufacturers. Popular options include units from EG4, Sol-Ark, and Growatt in the 3kW–5kW range. Prices typically $800–$1,500.

Battery

Parameter	Value
Chemistry	LiFePO4 (Lithium Iron Phosphate)
Capacity	5kWh (100Ah at 48V)
Nominal voltage	48V (51.2V actual)
Cycle life	4,000–6,000 cycles
Depth of discharge	90–100%
BMS	Built-in
UL listing	UL 9540A preferred

LiFePO4 is the correct chemistry for stationary solar storage:

No thermal runaway — inherently stable chemistry
Long cycle life — 10–15 years at daily cycling
Flat discharge curve — consistent voltage under load
Drop-in ready — built-in BMS handles cell balancing

Grounding and Bonding

All metallic components must be bonded to a grounding electrode system:

Equipment grounding conductor (EGC) — #6 AWG bare copper minimum, bonds all panel frames, racking, inverter chassis, and battery enclosure
Grounding electrode — Ground rod (8’ minimum) or existing building electrode, per NEC 250
Bonding jumper — Connects equipment ground to grounding electrode
Panel frame bonds — Each panel frame bonded to racking with listed grounding clips (WEEB or equivalent)

Bill of Materials

Solar Array

Item	Qty	Est. Cost
400W mono-PERC panels	8	$600–$1,200
Ground-mount racking system	1	$400–$800
Panel grounding clips (WEEB)	8	$40–$80
MC4 branch connectors (2-to-1)	2	$20–$40
PV wire, 10 AWG (100ft)	1	$60–$100

Power Electronics

Item	Qty	Est. Cost
Off-grid inverter/charger (3kW+)	1	$800–$1,500
5kWh LiFePO4 battery (48V)	1	$1,200–$2,000
DC disconnect (fused, 150V+)	1	$60–$120
DC breaker/fuses for strings	2	$40–$80

Electrical

Item	Qty	Est. Cost
AC breaker panel (small, 4-space)	1	$30–$60
GFCI breaker, 20A	1	$30–$50
Ground rod (8ft copper-clad)	1	$15–$25
Ground rod clamp	1	$8–$12
#6 AWG bare copper (50ft)	1	$40–$60
Conduit and fittings	—	$50–$100
Junction boxes, connectors	—	$30–$60
Wire (THHN, various gauges)	—	$50–$100
Labels (NEC-required, engraved)	Set	$30–$60

Total Estimated Cost

Scenario	Cost Range
Budget build	$3,500–$4,500
Mid-range	$4,500–$6,000
Premium	$6,000–$7,500

Wiring Topology

DC Source Circuit (Panels → DC Disconnect)

String 1: Panel 1 → Panel 2 → Panel 3 → Panel 4 ──┐
                                                      ├── MC4 Y-connector → DC Disconnect
String 2: Panel 5 → Panel 6 → Panel 7 → Panel 8 ──┘

Wire sizing (NEC 690.8):

I_sc per string: ~13A
Continuous current adjustment: 13A × 1.25 = 16.25A
Conduit fill adjustment: 16.25A × 1.25 = 20.3A
10 AWG PV wire — rated for 30A in conduit, satisfies NEC requirements
Use PV wire (USE-2/PV rated) for exposed outdoor runs, THHN in conduit

DC Disconnect → Inverter

Fused disconnect rated for string voltage × number of strings
Short-circuit current rating must exceed available fault current
NEC 690.15 requires a DC disconnect accessible to first responders

Battery Circuit

2 AWG minimum for 48V battery runs (verify with your inverter manual)
Keep battery cable runs as short as possible
Fused at battery with Class T or ANL fuse sized per inverter specs
Battery disconnect switch accessible without crossing live conductors

AC Branch Circuit

Inverter AC Output → 20A GFCI Breaker → Receptacle(s)

Standard 120V/20A branch circuit per NEC 210
12 AWG THHN in conduit
GFCI protection required (NEC 210.8)
Dedicated circuit — do not splice into existing building wiring

Labeling

NEC requires specific labels at specific locations. The inspector will check these. Use engraved or UV-resistant labels — not handwritten, not tape.

Required Labels

Location	Label Text
DC disconnect	”SOLAR PV DISCONNECT” — rated voltage and current
Inverter	”SOLAR PV SYSTEM” — rated output, AC and DC specs
Battery enclosure	”BATTERY STORAGE SYSTEM” — voltage, chemistry, capacity
AC output panel	”SOLAR PV AC OUTPUT — NOT CONNECTED TO UTILITY”
Ground-mount array	”WARNING: SOLAR PV ARRAY — ENERGIZED IN DAYLIGHT”
Each junction box	”SOLAR PV” with conductor identification
Main service panel (if nearby)	“THIS BUILDING HAS A SEPARATE SOLAR PV SYSTEM”

Step-by-Step Build

Phase 1: Planning and Permits

Site survey — Determine panel location (south-facing, minimal shading, ground mount preferred). Measure available area. You need roughly 180 sq ft for 8 panels.
Pull permit — Submit application to local building department. Include site plan, equipment spec sheets, and single-line wiring diagram.
Order equipment — While waiting for permit approval, order your panels, inverter, battery, and electrical materials. Lead times can be 1–3 weeks.

Phase 2: Mechanical Installation

Install ground-mount racking — Set posts/footings, level the racking rails. Follow manufacturer’s specs for spacing and tilt angle (latitude tilt is a good default).
Mount panels — Attach panels to racking with mid-clamps and end-clamps. Torque to manufacturer specs. Install grounding clips on each panel.
Run conduit — Install conduit from array to equipment location. Use outdoor-rated conduit (rigid or EMT) with proper fittings and weather heads.

Phase 3: Electrical — DC Side

Wire panel strings — Connect panels in series within each string. Use MC4 connectors (properly crimped, not the screw-on type). Verify string voltage with multimeter before proceeding.
Install DC disconnect — Mount fused disconnect between array and inverter. Land DC conductors on line side. Leave load side disconnected.
Run DC home runs — Pull PV wire through conduit from array to DC disconnect, then from disconnect to inverter location.

Phase 4: Rough-In Inspection

Schedule rough-in — Call your building department. Inspector will verify: conduit fill, wire gauge, grounding conductors, mounting integrity, disconnect rating. Do not energize the system before this inspection.

Phase 5: Electrical — AC Side and Battery

Install inverter — Mount inverter per manufacturer’s specs (ventilation clearances, orientation). Land DC conductors from disconnect.
Install battery — Position battery per manufacturer clearance requirements. Connect to inverter with properly sized cables and fused disconnect.
Wire AC output — Install sub-panel or breaker enclosure. Wire GFCI breaker, run to receptacle(s). Install all required labels.
Commission system — Close DC disconnect. Verify inverter startup, battery charging, AC output voltage. Test GFCI trip.

Phase 6: Final Inspection

Schedule final — Inspector will verify: labeling, GFCI operation, grounding/bonding continuity, overcurrent protection, voltage readings, overall workmanship. System must be energized.

Inspection Checklist

Use this checklist to self-inspect before calling for your official inspection:

Grounding and Bonding

Ground rod installed and accessible
Equipment grounding conductor connected to all frames and racking
Bonding jumper from equipment ground to grounding electrode
Panel grounding clips properly installed

Overcurrent Protection

DC fuses/breakers sized correctly for string current
Battery fuse sized per inverter manual
AC GFCI breaker installed and functional

Wiring

All connections torqued to spec
No exposed conductors outside rated enclosures
Conduit properly supported and sealed
Wire gauge matches circuit requirements

Labeling

All required labels in place (see labeling section)
Labels are engraved or UV-resistant
Labels legible and permanently attached

Safety

DC disconnect accessible and operational
Battery disconnect accessible
GFCI trips on test
No tripping hazards on conduit runs

Documentation

Permit posted at job site
Equipment spec sheets available for inspector
Single-line diagram available
Photos of covered work (rough-in)

Safety

This system operates at voltages that can injure or kill. Treat it with the same respect as any electrical system.

DC voltage is always present when panels are exposed to light. You cannot turn off the sun. Use opaque covers on panels when working on DC circuits.
Battery banks store significant energy. A short circuit across battery terminals can produce thousands of amps and cause arc flash. Always install and use the battery disconnect.
Work on one circuit at a time. Verify de-energized state with a multimeter before touching any conductor.
Wear appropriate PPE — insulated gloves rated for the voltage, safety glasses, closed-toe shoes.
Never work alone. Have someone nearby who knows where the disconnects are and how to call 911.

What’s Next

After this system is running:

Monitor your production — Track daily kWh output vs. expectations
Calculate your actual payback — Use the Rate Calculator to determine your real per-kWh grid cost
Consider expansion — Adding panels or battery capacity to an existing system is straightforward once the infrastructure is in place
Share what you learned — The best way to break the utility monopoly is to show your neighbors it works