Electrical capacity and utility service glossary

An estimate of how much additional load or generation specified equipment can accommodate under stated conditions. Its meaning depends on the equipment, operating limits, load assumptions and assessment date; a published value is not capacity reserved for a particular customer. Check which metric it describes before comparing sites.

An estimate of additional generation that can connect without exceeding the limits used in a utility’s assessment, such as voltage, thermal or protection limits. It addresses power supplied into the network. It cannot be used directly to determine how much additional customer demand the same location can serve.

The ability of a network or item of equipment to supply customer demand under specified operating conditions. A published figure may describe a total capability or the remaining allowance for additional load; establish which before comparing it with a project’s demand. The entire connection path can matter, including equipment downstream of the published asset.

The sum of the electrical input ratings of the equipment connected, or proposed to be connected, to an installation. It describes the equipment inventory, not necessarily the greatest simultaneous demand. Use consistent input ratings and units: a motor’s mechanical output rating is not its electrical input.

The rate at which a facility draws electrical energy, usually reported as average power over a specified interval. It is commonly expressed in kW, although some metering and billing use kVA. The averaging interval matters when interpreting peaks or comparing data.

The highest demand within a stated period and measurement interval. An observed annual peak, a forecast winter peak and an estimate for a new building are different inputs. For a connection assessment, establish how the project’s demand coincides with loading on the equipment that would serve it.

An estimate of combined demand that accounts for individual loads not reaching their maxima at the same time. Equipment schedules, cycling and seasonal use can make it lower than the sum of individual ratings or peaks. Utility forms can use the term differently, so document the assumptions and confirm the required calculation.

The expected cumulative demand at successive dates as a project enters service or expands. It lets the utility assess the initial connection separately from later requirements. State whether each figure is a total or an increment, and include the operating assumptions behind it.

The rated capability of the electrical service, commonly stated in amps at a specified voltage and phase configuration. It does not reveal existing demand, the permissible additional load within the installation or spare utility capacity upstream. Those require separate assessments; see what a building’s electrical service rating tells you.

Current is the rate at which electric charge flows; an ampere, or amp, is its unit. Cables and equipment have current limits because carrying current produces heating and other electrical effects. An amp rating alone does not establish a power rating: the voltage and supply configuration are also needed.

Voltage is the electrical potential difference between two points, measured in volts. It describes the energy transferred per unit of charge. The same current at different voltages represents different power levels, so an electrical service description needs both values and its phase configuration.

Real power is the rate at which electrical energy is transferred into uses such as heat, light and mechanical work, including losses. A kilowatt (kW) is 1,000 watts; a megawatt (MW) is 1,000 kW. A project’s kW requirement describes its demand at a given operating condition, rather than its energy use over a month.

Energy is the quantity delivered or consumed over time. A kilowatt-hour (kWh) is the energy used by a steady one-kilowatt load over one hour; a megawatt-hour (MWh) is 1,000 kWh. Monthly energy consumption does not show the peak demand that the connection must accommodate.

Apparent power expresses the combined voltage and current loading of an AC supply. It includes current associated with energy that moves back and forth between the supply and equipment, rather than being consumed as net energy; distorted current can also affect the relationship to real power. Equipment must carry the total current, which is why apparent-power ratings matter when assessing electrical capacity. It is measured in volt-amperes (VA), with 1,000 VA in a kVA and 1,000 kVA in an MVA.

The ratio of real power to apparent power for the same load and operating condition. At a given voltage, a load with a lower power factor draws more current to obtain the same real power, using more of the equipment’s current capacity. Use a supported value for the relevant load; do not assume every MVA figure converts to MW using the same factor.

Single-phase supply uses one alternating-voltage waveform; three-phase supply uses three waveforms offset by one-third of a cycle. This affects equipment compatibility and the relationship between voltage, current and power. A three-phase calculation must identify whether voltage is measured between lines or from a line to neutral; conductor count alone is not a sufficient description.

An initial request for the utility to assess a proposed location, load and service date. “Step Zero” is a name used in some utility processes, not a universal stage. The response can identify further work without reserving capacity or establishing a construction schedule.

A written utility response concerning its willingness or ability to serve a described project. Its wording may range from confirmation of service territory to a conditional assessment of a specified load. Check what it actually establishes about capacity, required work, timing and validity; the title alone does not establish a reservation or delivery commitment.

The submission that starts a defined utility service-request process, using the required forms and supporting information. It gives the utility a basis for review and any subsequent studies. An accepted application is not the same as an approved connection or an agreed delivery date.

An analysis of whether and how the utility system can accommodate a proposed connection or additional load. Depending on scope, it examines equipment loading, voltage, protection and other operating constraints, and identifies required changes. Its findings inform connection requirements and project planning, but a study result does not by itself reserve capacity, fix final costs or commit an energization date.

An allocation of capacity to a project under specified utility terms. Its amount, duration, conditions, required payments and treatment of project changes need to be established explicitly. A favorable screening result or nearby published headroom does not demonstrate that a reservation exists.

A load form is the utility’s template for describing the project’s electrical requirements. A load letter provides that information in a written statement, often prepared by an electrical professional. Both should distinguish equipment ratings, expected demand and timing; the utility determines the required format and supporting detail.

A simplified electrical drawing that represents circuits and equipment using single lines and symbols, rather than drawing every conductor. It shows how supplies, transformers, protection and loads connect. Reviewers use it to assess the proposed arrangement; it is not a substitute for a physical site layout.

A drawing showing the property and the physical arrangement of buildings, access, proposed electrical equipment and other relevant features. Utilities use it to assess routes, equipment locations and access requirements. The required detail, professional certification and municipal approvals vary by project and utility.

A right to use another party’s land for a specified purpose, such as installing, accessing and maintaining utility equipment. For a connection project, the location and permitted activities need to match the proposed works. An unresolved land right can affect whether and when the connection can be built.

A distribution circuit carrying power from a substation to an area or group of customers. Different sections and downstream equipment can have different constraints. A feeder-level capacity estimate does not establish the capability of every connection along it.

A facility containing equipment that switches, controls and often transforms electricity between voltage levels. A distribution substation can supply several feeders through one or more transformer banks. Those feeders can share an upstream constraint, so their individual capacity estimates cannot automatically be added into a deliverable total.

Equipment that transfers AC electrical energy between circuits, usually changing voltage. Its rating and operating limits affect how much load it can supply. A nameplate kVA or MVA rating is not a measure of spare capacity: existing load, operating conditions and other equipment limits also matter.

An additional utility supply path intended to maintain or restore service when the normal path is unavailable. The two paths can still share a transformer, substation, route or upstream supply, and transfer can involve an interruption. Assess the failures it protects against and the load it can restore; see redundant utility feeds: reliability, availability and cost.

The preferred source is the supply normally selected to serve the load; the alternate is the supply available for transfer under the agreed arrangement. These labels describe operating roles, not independence or guaranteed backup capacity. Confirm the alternate source’s capability and restrictions under the relevant outage conditions.

Equipment that transfers a load between power sources using a defined switching sequence. Its design determines whether transfer is automatic, the interruption involved and how the sources are isolated or briefly paralleled. The switch alone does not ensure that the alternate supply has sufficient capacity.