Manuall Trade Library Run your shop on Manuall

Generator Codes + Permits Reference

Reference Process Updated Jul 4, 2026 ยท Generator

Overview

Generator installation involves multiple code areas (electrical, gas/plumbing, building, environmental) + multiple permits. Cutting corners on permits creates legal liability + insurance problems. This reference covers the basics.

Applicable codes

National Electric Code (NEC)

Article 700 - Emergency Systems

  • Hospitals, life-safety equipment
  • Generally not applicable to residential standby

Article 702 - Optional Standby Systems

  • Most residential standby generators
  • Requirements for transfer switches, conductor sizing, etc.

Article 705 - Interconnected Electric Power Production Sources

  • For generators that interact with PV/grid
  • Solar + generator hybrid systems

Article 250 - Grounding + Bonding

  • Generator grounding requirements
  • Bond at generator OR at first overcurrent device

NFPA Codes

NFPA 110 - Standby Power Systems

  • Comprehensive emergency power standard
  • Levels (1: highest, 2: lower)
  • Class (length of run capacity)
  • Annual + monthly testing requirements

NFPA 70 - National Electrical Code

  • Same as NEC

NFPA 37 - Combustion Engines + Gas Turbines

  • Placement: 5 ft from openings; 25 ft from combustible buildings (or rated wall)
  • Refueling, fire protection

NFPA 54 - National Fuel Gas Code

  • Gas piping for generators
  • Pressure regulators

NFPA 58 - LPG Code

  • Propane tank placement + installation

International Codes (jurisdiction-specific)

IFGC - International Fuel Gas Code

  • Adopted by most US jurisdictions
  • Gas piping standards

IRC - International Residential Code

  • Residential building code
  • Construction details

Local amendments

  • Many municipalities have stricter requirements
  • Always check local building department

Typical permits required

Electrical permit

Required for:

  • Installing transfer switch
  • Running conduit
  • Connecting to main panel

Inspections:

  • Rough (before drywall, if applicable)
  • Final (post-install, transfer switch tested)

Cost: Varies by scope of electrical work; get a quote from the electrician.

Gas permit (or plumbing permit)

Required for:

  • New gas line to generator
  • Tee-off existing gas line
  • Increased gas demand requiring pipe upsizing

Inspections:

  • Pressure test
  • Final visual inspection

Cost: Varies by jurisdiction and pipe run length.

Building permit

Required for:

  • Concrete pad (in some jurisdictions)
  • Generator enclosure (if not pre-fab)
  • Wall reinforcement for cord connection box

Cost: Varies by jurisdiction and scope (pad, enclosure, wall reinforcement).

Air quality permit (some jurisdictions)

Required for:

  • Diesel generators (most cases)
  • Large gas generators in restricted air zones
  • Generators near hospitals/schools

Cost: Varies by jurisdiction; some areas charge ongoing fees.

HOA approval

Many HOAs have requirements:

  • Generator must be screened
  • Location restrictions
  • Color/aesthetic requirements
  • Noise limits

Always get HOA sign-off before scheduling work.

Placement requirements

Distance from house

  • NFPA 37: 5 ft minimum from openings (windows, doors)
  • Most local: 5-10 ft minimum
  • Quieter installations: position to minimize noise to bedrooms

Distance from combustibles

  • 5 ft from non-fire-rated wall (typical)
  • 3 ft from fire-rated wall
  • 20-25 ft from combustible structures separately

Distance from property line

  • 5-10 ft minimum (local code)
  • Some jurisdictions require fence/screening

Distance from gas meters / propane tanks

  • 10 ft minimum from gas meter
  • Specific to NFPA 58 for propane

Foundation / platform

  • Code requires solid, level base
  • Concrete pad: 4-6 inch thickness, slightly larger than generator footprint
  • Pre-fab composite pads acceptable in most jurisdictions

Noise codes

Generators are noisy (60-75 dB at 10 ft for residential).

Common limits:

  • Daytime: 60-65 dB at property line
  • Nighttime: 45-55 dB at property line

Mitigation:

  • Sound-attenuating enclosure (factory option, $$$ extra)
  • Position with intake/exhaust facing away from neighbors
  • Don't run during prohibited hours (some areas: 10pm-7am)

Customer should know noise expectations; some are surprised.

Air quality / emissions

EPA regulations:

  • Generators > 50 hp must meet specific emissions standards
  • Most residential standby below this threshold
  • Some states have stricter rules

State / local:

  • California has aggressive emissions rules
  • Air quality management districts (AQMD) regulate larger units

For most residential: standard manufactured-certified generators comply automatically.

Manufacturer compliance

Reputable manufacturers ship units meeting:

  • UL certification (electrical safety)
  • EPA emissions certification (most categories)
  • ANSI standards

Verify on data plate. Generator without certification may fail inspection.

Inspection checklist

When inspector arrives:

Electrical:

  • Conduit + wire sized correctly
  • Transfer switch wiring per NEC
  • Grounding adequate
  • Working clearance maintained
  • Labeling proper

Gas:

  • Pipe sized correctly
  • Pressure test results
  • Drip leg + shutoff installed
  • No buried valves
  • Leak test passed

Generator placement:

  • Distances met
  • Pad solid + level
  • Adequate clearance for service
  • Exhaust direction acceptable

Documentation:

  • Permits visible
  • Manufacturer literature on-site
  • Test results available

Common permit/inspection failures

  • No permit: red tag, work stops
  • Wrong conduit size: rework required
  • Inadequate working clearance: 30" wide, 36" deep at panel
  • Improper grounding: must be separately grounded if a derived system
  • Failed pressure test: re-pressure + retest
  • Wrong placement: too close to opening; move + repermit
  • Missing GFCI / breakers: install correctly

Working with the inspector

  • Be present at inspection
  • Have all paperwork ready
  • Have completed install ready to demonstrate (verify auto-start)
  • Be honest about anything not yet complete
  • Reschedule if needed (no surprises)

When permits aren't needed

  • Portable generators: typically no permit
  • Small standby (under 7 kW some areas): possibly no permit
  • Camp / rural areas: varies

Check local code; don't assume.

Maintaining permit records

For each install, retain:

  • Permit numbers
  • Plans submitted
  • Inspection reports
  • Pressure test certificates
  • Receipts of permit fees

These records can save legal trouble if generator-related fire OR accident occurs years later.

Code updates

Codes change every 3-6 years:

  • NEC updated every 3 years
  • NFPA codes updated periodically
  • Local adopts changes on different schedule

Stay current; what was code-compliant 5 years ago may not be today.

Penalty for non-compliance

  • Red tag (work stops)
  • Permit revocation
  • Insurance: policies often deny claims for unpermitted work
  • Fines: vary by jurisdiction, higher for major violations
  • Legal liability if accident occurs

References

  • NFPA 70, 110, 37, 54, 58
  • NEC Articles 700, 702, 705
  • IFGC, IRC, IFC
  • Local building department resources
  • Manuall internal: Whole-House Standby Generator Installation SOP, Transfer Switch Installation

Related articles