This is the real deal.
A permitted 3.2kW standalone solar system powers a small home outright or handles critical loads for a larger home. It’s built to code, inspected, and designed to last 25–30 years.
The utility company will try to complicate this. The permit process is straightforward. The technology is proven. Here’s the complete build guide.
What You’ll Build
A 3,200-watt (3.2kW) solar array with battery storage and a proper electrical infrastructure:
- 8× 400W monocrystalline panels (3,200W total)
- 2× 200Ah lithium battery modules (51.2V, ~20kWh usable)
- Hybrid inverter/charger (5kW capacity)
- Production monitoring
- Critical load subpanel (if grid-tied) or full panel (if standalone)
- All wiring, combiner boxes, disconnects, and overcurrent protection per NEC Article 690
What it powers at full capacity:
- All lighting in a 1,500 sq ft home
- Refrigerator + freezer
- Computers, TVs, entertainment
- HVAC fan (not compressor)
- Washer (not dryer)
- Small water pump
What it won’t power without expansion: Central air conditioning compressors, electric ranges, electric water heaters, or large 240V loads.
System Design
Panel Specification
400W monocrystalline panels (8 panels × 400W = 3,200W)
Array configuration options:
- 2 strings of 4 panels in series: Nominal 200V DC input, good for MPPT efficiency
- 4 strings of 2 panels in series: Lower voltage, requires larger wire gauge
For most installations: 2 strings of 4 panels
Panel specs (verify with specific manufacturer):
- Voc: ~49V per panel
- Isc: ~10A per panel
- String voltage (4 panels × 49V Voc): ~196V at open circuit
- String current: ~10A
Inverter Selection
For a standalone system: a hybrid inverter/charger that handles both solar MPPT and battery management in one unit.
Key specifications:
- Solar input: ≥3,200W, compatible with your string voltage
- Battery voltage: 48V nominal (for LiFePO4 battery bank)
- Output: 5kW continuous (120/240V split-phase for US installations)
- Grid-tie capability: Optional, allows net metering if grid is available
- Pass-through: For grid or generator backup
Popular options in this range: Growatt, Sol-Ark, Victron. Verify UL listing for your jurisdiction.
Battery System
LiFePO4 (Lithium Iron Phosphate) is the standard for new residential installations.
Target: 20kWh usable capacity
- Provides 1.5–2 days of autonomy for the loads listed above
- 2× 10kWh modules at 51.2V nominal
LiFePO4 advantages over lead-acid:
- 3,000–5,000 cycle life vs. 300–500 for lead-acid
- 80–90% usable depth of discharge vs. 50% for lead-acid
- Stable voltage throughout discharge
- No off-gassing; can be installed indoors
Racking and Mounting
For pitched roofs: rail-based mounting systems.
- Unirac, IronRidge, or equivalent for roof-mount
- Lag bolts into rafters — locate rafters before ordering
- Flashing at every penetration — no exceptions
Bill of Materials
| Item | Quantity | Unit Cost | Extended |
|---|---|---|---|
| 400W monocrystalline panels | 8 | $200–$280 | $1,600–$2,240 |
| Hybrid inverter/charger 5kW | 1 | $1,200–$2,000 | $1,200–$2,000 |
| 10kWh LiFePO4 battery module | 2 | $3,000–$5,000 | $6,000–$10,000 |
| Roof mounting system (rail + hardware) | 1 system | $400–$700 | $400–$700 |
| DC combiner box (if >2 strings) | 1 | $60–$120 | $60–$120 |
| AC/DC disconnect switches | 2 | $80–$150 | $160–$300 |
| Wire (PV wire, THWN, various) | Lot | — | $200–$400 |
| Conduit and fittings | Lot | — | $150–$300 |
| Breakers and overcurrent protection | Lot | — | $100–$200 |
| Monitoring hardware | 1 | $100–$200 | $100–$200 |
| Permit fees | — | Varies | $100–$500 |
| Total (DIY, excluding labor) | $3,500–$7,500 |
Professional installation typically adds $6,000–$15,000 for a system this size. The 30% ITC applies to labor costs as well as equipment.
The Permit Process
Pull the permit. No exceptions.
Unpermitted solar:
- Can void your homeowner’s insurance if there’s a fire
- Creates problems when you sell the home
- May require expensive removal if discovered
The permit process for residential solar is standardized in most jurisdictions:
Step 1: Prepare plan set
- Site plan showing panel location and dimensions
- Single-line electrical diagram (most jurisdictions accept standard format)
- Equipment cut sheets for all major components
Step 2: Submit permit application
- Local building department (not utility — that’s a separate step)
- Typical processing: 1–4 weeks
- Some jurisdictions have online permit portals and expedited solar review
Step 3: Install
- Install per approved plans
- Don’t deviate from plans without an amendment
Step 4: Inspection
- Call for inspection after rough-in and after final
- Inspector verifies NEC Article 690 compliance
- Common failure points: labeling, disconnect accessibility, conduit fill, grounding
Step 5: Interconnection (if grid-tied)
- Submit interconnection application to your utility
- Timeline varies: 2 weeks to 6 months depending on utility
- Utility installs bidirectional meter
Wiring Topology
[8× 400W Panels]
↓ (2 strings × 4 panels)
[DC Combiner] → [Disconnect]
↓
[Hybrid Inverter/Charger]
↓ ↓
[Battery Bank] [AC Output]
(2× 10kWh LiFePO4) ↓
[Main Panel / Subpanel]
↓
[Critical Loads]Required Labeling (NEC 690)
The inspector will fail you without proper labels. Required at minimum:
- AC disconnect: “PV SYSTEM DISCONNECT”
- DC disconnect: “CAUTION — SOLAR ELECTRIC SYSTEM — DISCONNECT BEFORE SERVICING”
- Main panel: “CAUTION — DUAL POWER SOURCE — THIS BUILDING HAS A SOLAR ELECTRIC SYSTEM”
- Meter: Warning label per local utility requirements
- Rapid shutdown: Rapid shutdown label per NEC 690.56
Get pre-printed NEC-compliant labels — they’re inexpensive and inspectors know the difference.
Inspection Checklist
- All equipment is UL or equivalent listed
- Panels are grounded per NEC 690.43
- Array wiring uses PV-listed wire (not standard THWN) in exposed runs
- Conduit used wherever wire is accessible
- Conduit fill does not exceed NEC limits
- AC and DC disconnects accessible and labeled
- All required warning labels installed
- Rapid shutdown system installed (required for buildings per NEC 690.12)
- Inverter output breaker matches inverter specs
- Battery installed per manufacturer specs (ventilation if required)
- Single-line diagram posted at main panel
Safety
Solar systems produce lethal DC voltages. A fully lit 4-panel string produces ~196V DC — enough to kill. A 48V battery bank can deliver enough current through a short to cause severe burns or fire.
Work with the array covered whenever you’re making connections. Tarps or cardboard on the panels.
Never work on the system live. Disconnect all sources — grid, battery, array — before touching wiring.
Use insulated tools. Invest in proper electrician’s tools rated for the voltage you’re working with.
If you’re not comfortable with electrical work at this scale, hire a licensed electrician for the DC wiring. The permit process is the same regardless of who does the work.
What’s Next
You just built a real system. You’re generating your own power, independent of the monopoly’s meter, on equipment that will outlast most car loans.
From here:
- Understand your incentives: Federal ITC & State Credits →
- Buy American: Domestic Content Bonus →
- Know your rate: Why Rate Calculators Matter →
The utility company still charges your neighbor $150/month. You know how this works now.
DATA SOURCED FROM: National Electrical Code (NEC) Article 690 — Photovoltaic Systems; NREL — PVWatts system sizing; Manufacturer specifications for listed equipment. Individual results vary by location, system size, and local rates.