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

480Y/277V three-phase (commercial): the same wye shape one step up. 277V is measured hot-to-NEUTRAL, which is what the lighting runs on, and 480V is hot-to-hot, which is what the motors run on. 277 is not taken across two hots; getting that backwards is how a 277V ballast ends up on 480.

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 keep the calculated service below the arithmetic sum of every nameplate, because not everything runs at once: the optional dwelling calculation in NEC 220.82 is the one to reach for on a single dwelling, 220.84 covers multifamily, and 220.61 handles the neutral load separately.

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: two documents apply and you dig to the deeper one. NEC Table 300.5 sets the code minimum by wiring method and by what is on top of it, and the serving utility's own service manual routinely requires more on a lateral it will own or splice. Get the utility spec before you trench, because re-digging a lateral is the single most avoidable callback on a service upgrade. 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