Service Entrance + Meter Base Reference

Why this matters

Service entrance is the link between the utility + the customer's electrical system - the conductors, mast / pipe / cable, meter base, + main disconnect. Failure here = no power to the whole house + a utility-coordination service call that costs more than the work itself. Knowing the configurations, code requirements, + utility coordination saves customers from preventable outages + saves you from the awkward "I'll need to call the utility" phone call mid-job. This is the foundation for service upgrades, generator interconnections, + solar interconnections - three of the highest-margin specialty electrical jobs.

Service entrance components

Service drop / service lateral - utility-owned conductors from the pole / underground to the customer's weather head OR meter base.

Weather head (overhead service) - fittings at the top of the service mast where utility connects.

Service mast (overhead) - rigid metal conduit OR pipe going from weather head down to the meter base on the side of the house.

Service entrance conductors (SEC) - wires from the weather head OR meter to the main disconnect.

Meter base / meter pan - utility-owned device that measures consumption; the customer's electrical service connects through this point.

Main disconnect / service disconnect - breaker that disconnects all power to the dwelling. Could be on the meter base OR a separate panel.

Grounding electrode + bonding - covered in detail in Grounding + Bonding Fundamentals.

Overhead vs underground service

Overhead (older + rural):

• Utility drop from pole to weather head on house
• Mast or pipe down through the eaves to meter base
• More exposed to weather + wildlife
• Easier to access for utility maintenance
• Lower install cost

Underground (lateral):

• Conduit from utility-side pad / transformer underground to meter base
• Safer + more reliable
• More expensive to install + repair
• Common in new construction + suburban subdivisions

Service voltages

120/240V single-phase (typical residential):

• Two hot conductors at 120V from each to neutral
• 240V between the two hots
• Neutral provides return for 120V loads
• 100, 125, 150, 200, 320, 400 A service sizes

120/208V three-phase (light commercial, some condos):

• Three hot conductors + neutral
• 120V hot-to-neutral
• 208V hot-to-hot (or 277V single-phase off two hots in 480 systems)

240/120V high-leg delta (older commercial):

• Three hots; one "high leg" at 208V to neutral, two at 120V
• Less common; replaced by 120/208Y

Service sizing

Sized per NEC 220 calculation. Standard residential: 1,500 sq ft typically 100A, 2,500 sq ft 150A, 3,500 sq ft 200A; custom home with electric heat + multiple EVs + solar/battery: 320A, 400A, or paired services. Calculation: general lighting 3 VA/sq ft + small appliance circuits (2 × 1,500 VA) + laundry (1,500 VA) + specific appliances at nameplate + larger of heating/cooling + continuous loads at 125%; total VA / voltage = amperes. Demand factors per NEC 220.61 + 220.84 allow undersizing actual peak.

Meter base types

100A pedestal/pad (small home), 150A (mid-size), 200A (most common modern), 320A or 400A (large home + EV + electrification). Combination meter/breaker (CSED) integrates meter + main breaker + sub-bus in one enclosure (100 - 320A typical, common in retrofits). Meter/main + separate sub-panel: meter outside, main disconnect + branch panel inside (common in commercial + larger residential).

Service mast / pipe (overhead service)

Conduit: RMC (most jurisdictions require), IMC also common, PVC schedule 80 jurisdiction-dependent; EMT NOT permitted. Size 2" or 2.5" for 200A residential typical. Bracing: angle iron bracket bolted to roof rafter; mast cannot move under wind or utility-wire load. Through-roof: extends 18" above roof for clearance, sealed flashing (lead, neoprene, rubber boot). Weather head: bell-shape at top, conductors exit sealed against precipitation, drip loop prevents water following into mast.

Service lateral (underground)

Conduit: PVC schedule 40 or 80 most common (cheaper); RMC for short distances. Depth: 24" min residential; 36" under driveways/parking. Sweeps: 90° large-radius elbows; one per conduit run. Pull rope through during install for future pulls.

Meter base installation

Location: 4 - 6 ft above grade (utility-spec varies), accessible without ladder, within 6 ft of property line or per utility easement. Mounted to support meter pull-out forces; weather-sealed. Service-side conductors are utility's (sized + protected); customer's side starts after meter base. Customer conductors: sized per service rating, outdoor wet-location insulation (XHHW-2, USE-2, RHW-2), red + black hots + white/identified neutral + ground.

Main disconnect

Required for every dwelling. Location: within sight of meter base OR indoors immediately adjacent to where service conductors enter. Type: standard breaker (Square D QO, Eaton CH, Cutler-Hammer); fused less common in residential; lockable for safety + utility shutoff. Size matches service rating.

Utility coordination

Service upgrade sequence: customer permit with AHJ, plan reviewed by AHJ, plan submitted to utility for service approval, utility coordinates new transformer/drop, electrician mechanical install (mast + meter base + wiring), utility shut-off scheduled (4 - 8 hrs), customer + utility on-site for swap, AHJ inspection, utility re-energizes. Coordination is the slow part - utility may take 4 - 12 weeks for service-side work. Set customer expectations.

Common service-entrance issues

Loose connection at meter base - utility-side (call utility, not customer responsibility) vs customer-side (tighten + verify). Corroded connections typically utility-side first; customer can request utility inspection. Water intrusion at weather head/mast: re-seal flashing + drip loop. Inadequate clearance over roof/driveway per NEC 230.24 - usually utility's issue. Service capacity exceeded: main breaker trips on whole-house load; need service upgrade or smart panel.

References

• NEC 230 (Services)
• NEC 240 (Overcurrent Protection)
• NESC (National Electrical Safety Code - utility side)
• Utility-specific service rules (varies by utility)
• Manuall internal: Service Panel Upgrade, Grounding + Bonding Fundamentals