Rough Electrical Installation
Rough electrical is your one chance to get wiring right before walls close up. This phase includes installing the subpanel, running circuits for all appliances and outlets, and ensuring proper safety protection. Think ahead—adding outlets now costs almost nothing, but adding them after drywall is expensive and messy.
Quick Summary
Time needed
2-4 days
Cost range
$3,000-$8,000
Professional
Licensed electrician
Why Rough Electrical Matters
Your ADU's electrical system needs to handle kitchen appliances, HVAC, bathroom ventilation, lighting, and everyday electronics. A properly planned electrical system ensures safety, meets code requirements, and provides enough capacity for your needs. Common issues from poor planning include:
- Tripping breakers when running multiple appliances
- Not enough outlets, leading to extension cord overuse
- Failed inspections due to missing GFCI/AFCI protection
- Expensive retrofits to add circuits after drywall
Step-by-Step Rough Electrical Guide
Size and Install the Subpanel
Most ADUs need a 60-100 amp subpanel fed from the main house panel. Your electrician will determine the exact size based on your load calculations:
- • 60 amp: Basic ADU with gas appliances, mini-split
- • 100 amp: All-electric ADU, electric range, heat pump
- • 200 amp: Large ADU with EV charging, multiple heat pumps
Pro tip: Size up if budget allows. A larger panel costs only $200-400 more but provides flexibility for future needs like EV charging.
Run Dedicated Circuits for Major Appliances
Code requires dedicated circuits for certain appliances. Plan for:
- • Kitchen: Refrigerator (20A), dishwasher (20A), microwave (20A)
- • Range/Oven: Electric range (40-50A) or gas range (15A)
- • Bathroom: Bathroom receptacles (20A GFCI)
- • HVAC: Mini-split or furnace (varies by unit)
- • Water heater: Electric tank (30A) or tankless (varies)
- • Washer/Dryer: Washer (20A), electric dryer (30A)
Install GFCI Protection in Wet Areas
Ground Fault Circuit Interrupter (GFCI) protection is required in areas with water exposure:
- • Kitchen counter receptacles within 6 feet of sink
- • All bathroom receptacles
- • Laundry area receptacles
- • Outdoor receptacles
- • Garage receptacles (if applicable)
Note: You can use GFCI breakers at the panel or GFCI outlets. GFCI breakers protect the entire circuit; GFCI outlets protect downstream outlets.
Install AFCI Protection in Living Spaces
Arc Fault Circuit Interrupter (AFCI) protection prevents electrical fires and is required in most living areas under current code:
- • Bedrooms (required since 1999)
- • Living rooms, family rooms
- • Dining rooms
- • Hallways, closets
- • Most other habitable rooms
AFCI breakers cost $30-50 each vs. $5-10 for standard breakers, but they're required by code and significantly reduce fire risk.
Plan Outlet and Switch Locations Generously
Now is the time to add outlets liberally. Code minimums are often not enough for modern living. Consider:
- • Living areas: Outlet every 6 feet on walls (code minimum: 12 feet)
- • Kitchen: Counter outlets every 4 feet, plus islands
- • Bedroom: Outlets on each side of bed location, plus desk area
- • Bathroom: Outlet near vanity, consider separate for electric toothbrush
- • USB outlets: At nightstands, kitchen counter, home office
- • Outdoor: Front and back of ADU minimum
Money saver: Adding an outlet during rough-in costs $20-50. Adding one after drywall costs $150-300. Be generous now.
Install Lighting Circuits and Boxes
Plan your lighting layout carefully. Include:
- • Ceiling boxes for overhead lights (recessed can locations)
- • Switch locations at room entries (3-way for multiple entrances)
- • Under-cabinet lighting circuits in kitchen
- • Bathroom vanity light and exhaust fan circuits
- • Outdoor lighting circuits (porch, pathway)
- • Consider dimmer-compatible wiring throughout
Run Low-Voltage Wiring
Don't forget communication and data wiring:
- • Ethernet: Cat6 to living room, bedroom, office areas
- • Coax: If cable TV service is planned
- • Smart home: Consider wiring for smart switches, thermostats
- • Doorbell: Video doorbell wiring at entry
- • Security: Conduit for future security system if desired
Typical ADU Circuit Requirements
| Circuit | Amperage | Wire Size |
|---|---|---|
| General receptacles | 15A or 20A | 14 AWG or 12 AWG |
| Kitchen counters | 20A (2 circuits min) | 12 AWG |
| Refrigerator | 20A dedicated | 12 AWG |
| Electric range | 40A or 50A | 8 AWG or 6 AWG |
| Bathroom | 20A GFCI | 12 AWG |
| Mini-split HVAC | 15A-30A | Per manufacturer |
| Electric water heater | 30A | 10 AWG |
| Electric dryer | 30A | 10 AWG |
Rough Electrical Inspection Checklist
Your work must pass inspection before drywall can be installed. Inspectors will verify:
Frequently Asked Questions
Can I do rough electrical myself?
In most jurisdictions, only licensed electricians can perform permitted electrical work. Even where homeowner work is allowed, the subpanel connection typically requires a licensed professional. DIY electrical work can void insurance and create safety hazards. This is one trade where hiring a pro is strongly recommended.
How much does rough electrical cost for an ADU?
Typical range is $3,000-$8,000 depending on ADU size, number of circuits, and local labor rates. A 400-500 sq ft ADU with standard electrical might cost $3,000-4,500. A larger ADU with all-electric appliances and extensive lighting could be $6,000-8,000+. Get 3 quotes from licensed electricians.
What's the difference between GFCI and AFCI?
GFCI (Ground Fault Circuit Interrupter) protects against shock by detecting current leakage to ground—required in wet areas. AFCI (Arc Fault Circuit Interrupter) protects against fires by detecting dangerous electrical arcs—required in living spaces. Modern code often requires combination AFCI/GFCI protection in some locations.
Do I need to upgrade my main panel?
Possibly. If your main house panel is already near capacity (common in older 100A panels), you may need to upgrade to 200A before adding an ADU subpanel. Your electrician will perform a load calculation to determine if an upgrade is needed. Budget $2,000-4,000 for a panel upgrade if required.
Ready for the Next Step?
Once rough electrical passes inspection, you'll move on to rough plumbing—installing water supply lines, drain pipes, and vent stacks before the walls close up.