Connected load, demand, peak and ramp-up

Connected load is the sum of the nameplate ratings of everything wired into a building. A nameplate is the label on a piece of equipment giving its rated power. Add every fixture, rooftop unit, motor and charger and the total, usually stated in kW, is the connected load.

Demand is the power the building actually draws, averaged over a short interval. Peak is the highest demand recorded over a stated period, such as a month or a year. For a building that does not yet exist, a form asks for an estimate of that highest figure, so the number is stated by the applicant and has not been measured. National Grid’s Load Sheet separately requests total diversified load without defining the calculation. Confirm the intended treatment rather than assuming it is identical to an expected-peak figure.

Connected load can exceed coincident peak demand for two reasons. Equipment seldom all runs at once, and running equipment often draws less than its nameplate. Dock doors, conveyors and chargers each have their busy hours, and heating and cooling units cycle on and off.

For a hypothetical warehouse, assume electrical input ratings of 120 kW of lighting, 300 kW of HVAC (heating, ventilation and air conditioning), 250 kW of dock and conveyor equipment, and 180 kW of forklift battery chargers. The sum is 850 kW. Assume an independently assessed coincident peak of 520 kW, about 61 percent of the connected total (520 divided by 850).

Forms ask for load by type because each type behaves differently across a day. National Grid's Load Sheet lists inside lighting, outside lighting, electric heating, air conditioning, water heating, refrigeration, additional equipment and motors, each with kW and hours of use per year. Lighting follows occupancy, HVAC follows weather, process equipment (machinery that makes or moves the product) follows the production schedule, and chargers can often be set to run at night. A reader of the breakdown can see when the peak is likely to fall and which parts of it could shift. If the individual peaks occur at different times, their sum exceeds the building’s coincident peak. That relationship must be assessed from the proposed operating profile.

Ramp-up

A ramp-up schedule lists when a site's load arrives in stages. For a phased project, initial demand may be below the eventual peak. A warehouse fills racking and adds conveyor lines. A manufacturer commissions one production line, then a second. A charging depot energizes a few stalls and adds more as vehicles arrive.

For the same hypothetical project, assume the following commissioning schedule. In January 2028 the building opens with an expected peak of 200 kW. In July 2028 the freezer wing is commissioned and the expected peak rises to 350 kW. In March 2029 the charging room is complete and the expected peak reaches the full 520 kW. Each figure is cumulative, and each date is the applicant's estimate.

A utility asks for the dates because its own work is scheduled against them. Include the cumulative load schedule in the inquiry so the utility can distinguish initial requirements from later expansion. Equipment is ordered ahead and construction takes time, so a request for 520 kW in January 2028 can be planned differently from 200 kW then and 520 kW fourteen months later (January 2028 to March 2029). A single in-service date implies the whole load at once.

Dates an applicant lists are requested dates. Read the utility’s response for its scope and conditions before using those dates in a project schedule.