Meter Base Symbol
Definition: The Meter Base symbol represents the utility-owned socket enclosure mounted at the service entrance that accepts a kilowatt-hour (kWh) revenue meter, connecting the incoming service conductors from the utility to the downstream load-side conductors feeding the main panel, used in electrical wiring diagrams to indicate the metering interface between the utility and the customer's electrical system.
Also known as: electric meter socket, meter socket, meter enclosure, kWh meter base, utility meter base, revenue meter socket, EL1 meter can.
What the Meter Base symbol means
The Meter Base symbol denotes the weatherproof socket assembly installed at the service entrance between the utility's service-drop conductors and the building's service-entrance conductors. The Line pins receive the two hot conductors (L1 and L2 at 120 V each, 240 V between them) from the utility, and the Load pins feed the same conductors downstream to the main panel. The revenue meter (kWh meter) plugs into the meter base jaw contacts to measure energy consumption.
In electrical wiring diagrams the meter base symbol marks the point of demarcation between the utility's metered service and the customer's internal distribution system. The meter base is typically utility-owned and must be installed to the utility's specifications, while the building wiring from the meter base to the main panel is the customer's responsibility under NEC Article 230.
How to identify the Meter Base symbol
The symbol is drawn as a rectangular block labelled 'Meter Base' or 'Meter'. Two pins emerge from the top — Line L1 and Line L2 — representing the utility service-entrance conductors feeding into the meter. Two corresponding pins emerge from the bottom — Load L1 and Load L2 — representing the conductors leaving the meter base toward the main panel. A circle within the rectangle may represent the meter dial/disc or the plug-in meter socket.
Function in a circuit
The meter base provides mechanical mounting and electrical connection for a revenue meter (typically a solid-state or electromechanical kWh meter). The line-side jaw contacts carry the full service current to the meter's current transformers (or series-connected current coils). The meter measures energy consumption by multiplying voltage and current (proportional to watts) and integrating over time (watt-hours). The metered current then passes through the meter's load-side jaws to the downstream load conductors. Utility companies read the meter register to bill the customer for energy consumed in kilowatt-hours (kWh).
Standards: IEC vs ANSI
| IEC 60617 | IEC 62053 series governs electricity metering equipment. IEC 60617 does not define a dedicated meter-base glyph; the meter base is represented as a watt-hour meter symbol (circle with 'kWh' label) per IEC 60617-09. |
|---|---|
| ANSI/IEEE 315 | ANSI C12.1 (Code for Electricity Metering) and ANSI C12.10 (Physical Aspects of Watthour Meters) govern meter base socket requirements in North America. NEC Articles 230 and 110 govern service-entrance and meter-base installation. ANSI Y32.2 / IEEE 315-1975 represents the meter as a circle with the letter W or kWh. |
| Key difference | IEC diagrams use the kWh meter symbol (circle with kWh label) per IEC 60617-09; ANSI/IEEE diagrams use a circle with W, Wh, or kWh designator per IEEE 315-1975. The meter base enclosure is a North American concept tied to the ANSI socket meter standard; IEC countries more commonly use DIN-rail mounted meters. |
Terminals / pins
| Pin | Name |
|---|---|
| line | Line |
| load | Load |
Typical values
Service voltage: 120/240 V AC split-phase (North America). Current ratings: 100 A, 150 A, 200 A (residential meter sockets). Number of service conductors: 3 (L1, L2, neutral/ground). Meter socket form factors: ANSI socket Form 2S (single-phase 2-wire), Form 2S3 (single-phase 3-wire, most common residential). Jaw contact rating: 200 A continuous.
Where the Meter Base symbol is used
- Residential service entrance diagrams showing the utility-to-customer connection point
- Commercial building electrical one-line diagrams identifying the metering location
- Solar PV and net-metering interconnection diagrams showing bi-directional meter placement
- Multi-tenant sub-metering systems where each unit has an individual meter base
- Temporary power service diagrams for construction sites requiring utility metering
- Electric vehicle service equipment (EVSE) dedicated service diagrams requiring separate metering
Example
In a residential service entrance diagram, the meter base symbol shows Line L1 and L2 entering from the utility service drop at the top, connected through the revenue meter to Load L1 and L2 exiting the bottom. The load pins feed the main panel symbol below, which shows a 200 A main breaker and branch-circuit positions. A grounding electrode conductor connects the main panel ground bus to a copper ground rod driven 8 ft into the earth, per NEC 250.52.
Key facts
- The Meter Base symbol represents the utility meter socket that accepts a plug-in kWh revenue meter, connecting utility service-entrance conductors (Line) to customer load conductors (Load).
- Four pins define the symbol: Line L1 and Line L2 (utility supply side, entering from the top), and Load L1 and Load L2 (customer distribution side, exiting from the bottom).
- The revenue meter measures electrical energy in kilowatt-hours (kWh) by integrating instantaneous power (watts) over time.
- ANSI C12.10 defines the physical socket standard for North American residential meter bases; utility meters must be ANSI Form 2S3 compatible for split-phase 120/240 V service.
- The meter base is typically utility-owned and installed to the utility's specification; tampering with the meter seal is a criminal offence in most jurisdictions.
- In solar net-metering systems, a bi-directional or dual-element meter is installed in the same meter base socket to record both import (consumption) and export (generation) energy.
- IEC 62053 governs kWh meter accuracy classes; Class 1 meters have ±1% accuracy, Class 0.5 meters ±0.5% accuracy.
Diagrams that use this symbol
- single phase meter connection
- single phase energy meter diagram
- ct connection diagram
- electric meter connection diagram
- electric meter wiring diagram
- single phase meter wiring diagram
- residential electric meter box wiring diagram
- 3 phase energy meter connection diagram with ct
Frequently asked questions
What does the meter base symbol mean in a circuit diagram?
The meter base symbol represents the utility meter socket at the service entrance, where the utility's revenue kWh meter plugs in. It shows the physical and electrical interface between the utility's service conductors (Line L1, L2) and the customer's building wiring (Load L1, L2 feeding the main panel), marking the metering and demarcation point.
What do the Line and Load pins mean on the meter base symbol?
The Line pins (L1 and L2) are the utility supply side of the meter base, connected to the incoming service-drop conductors from the utility transformer. The Load pins are the customer side, connected to the service-entrance conductors feeding the main panel. Current flows from the utility through the meter (where consumption is measured) to the Load pins and into the building distribution system.
What is the difference between a meter base and a main panel?
The meter base is the utility-owned metering socket at the service entrance; it only measures energy and passes current through to the downstream wiring. The main panel (load centre) is the customer-owned distribution board that contains the main breaker and individual branch-circuit breakers. In most residential installations, the meter base is mounted outside the building and the main panel is inside.
What size meter base do I need for 200 A service?
A 200 A meter base socket (rated for 200 A continuous) with ANSI Form 2S3 socket type is the standard for modern 200 A residential service in North America. The meter base must be rated to match or exceed the service ampacity, and the specific socket form must match the utility's standard meter plug (most utilities use Form 2S or 2S3 for single-phase three-wire service).
Can the meter base be used for net metering with solar panels?
Yes. Net metering uses a bi-directional kWh meter installed in the standard meter base socket. When solar generation exceeds consumption, current flows backward through the meter, registering exported energy as a credit. Some utilities require a two-channel meter (net meter) that separately records import and export rather than simply spinning backward.
What standard governs the meter base in North America?
ANSI C12.10 (Physical Aspects of Watthour Meters) defines the socket dimensions and jaw-contact specifications for North American meter bases. ANSI C12.1 governs electricity metering code requirements. NEC Articles 230.66 and 110.14 govern service-entrance metering enclosure installation. Internationally, IEC 62053 governs electricity meter accuracy and performance.
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