Electrical load calculation worksheet

What an electrical load calculation worksheet does

A load calculation gives the minimum calculated load a feeder or service has to carry. It isn't a measurement of what the building will draw: Article 220 builds the number from unit loads, outlet counts and nameplate ratings, then applies the demand factors the code allows. Engineers use it to size services and feeders, plan reviewers check it, and estimators run it to sanity check the gear on a design-build job or to price an alternate when the drawings don't show a full panel schedule.

The worksheet above follows the order of Part III of Article 220 (feeder and service load calculations). Every line shows the code section it came from, whether it's added to the total, and the volt-amperes it contributes. The 2023 edition reorganized Article 220, so older worksheets cite different section numbers for the same rules: the non-dwelling lighting unit loads that used to be Table 220.12 are now Table 220.42(A), and the lighting demand factors that were 220.42 are now 220.45³.

How to do a commercial electrical load calculation

1. General lighting. Multiply the floor area, measured from the outside dimensions of the building per 220.5(C), by the unit load for the occupancy in Table 220.42(A). The table note says the 125% continuous-load multiplier is already included, so don't apply it again¹.
2. Lighting demand factors. Table 220.45 only reduces general lighting for dwelling units, hotels and motels (including apartment houses without tenant cooking), and storage warehouses. Every other occupancy is at 100%¹.
3. Receptacles. Count general-use receptacle outlets at 180 VA for each single or multiple receptacle on one yoke (220.14(I)). Table 220.47 lets you take the first 10 kVA at 100% and the remainder at 50%. In office buildings, the receptacle load is the larger of that result and 1 VA/ft² (220.43)¹.
4. Show windows, track and signs. Show windows at 200 VA per linear foot (220.46(A)), lighting track at 150 VA for every 2 ft or fraction (220.46(B)), and each required sign circuit at 1,200 VA (220.14(F))¹.
5. Motors and HVAC. Use the ratings required by 430.24 and Article 440 (220.50), and add 25% of the largest motor. Fixed space heating counts at 100% (220.51). Where heating and cooling won't run at the same time, 220.60 lets you count only the larger¹.
6. Continuous loads. For conductor sizing, 215.2(A)(1) requires the noncontinuous load plus 125% of the continuous load². The worksheet applies 125% to anything you mark as continuous.
7. Amps. Divide the total VA by the voltage (single phase) or by the voltage times 1.732 (three phase). Section 220.5(B) allows rounding to the nearest whole ampere¹.

NEC Table 220.42(A): general lighting loads by occupancy

The informational note under 220.42(A) warns that these values are based on minimum load conditions and 80% power factor and might not cover the installation contemplated. When the lighting design is known, the actual connected load of the luminaires is often higher or lower than the table. Section 220.42(B) allows energy code unit values instead, but only with a power monitoring system that alarms on excess lighting load, no Table 220.45 demand factors, and the 125% multiplier applied¹.

Demand factors used in the worksheet

The hotel factors don't apply to feeders serving areas where all the lighting is likely to be on at once, such as ballrooms and dining rooms. Demand factors also never reduce the number of branch circuits for general illumination: 220.45 says so directly¹.

Worked example: a 12,000 ft² office

These are the calculator's default inputs. The equipment ratings are illustrative, not from a real project.

Commercial electrical load calculation worksheet in Excel

Most commercial electrical load calculation worksheet Excel files do the same thing as the calculator: a row per load, a column for the basis, a column for VA. "Download as CSV" writes the worksheet with four columns (step, basis, VA, counted in total) followed by the total and the amps for each system. Excel, Google Sheets and Numbers open it directly, so you can add your own rows, insert it into a submittal, or keep it with the bid. "Copy worksheet" puts the same table on the clipboard as tab-separated text that pastes into spreadsheet cells.

Nothing is sent to a server. The page does the arithmetic in your browser, which also means it doesn't remember your inputs after you close it: download the CSV if you want to keep them.

Dwelling unit standard method

Switch the building type to "Dwelling unit" for the standard method. General lighting and general-use receptacles are 3 VA/ft² (220.41), and no separate receptacle load is added. Add 1,500 VA for each small-appliance circuit (210.11(C)(1) requires two or more) and 1,500 VA for each laundry circuit (220.52), then apply the Table 220.45 dwelling demand factors. A 2,000 ft² unit with two small-appliance circuits and one laundry circuit has 10,500 VA before demand and 5,625 VA after¹.

Then add the rest: electric dryers at 5,000 VA or the nameplate, whichever is larger (220.54); EV chargers at 7,200 VA or the nameplate (220.57); 75% of the nameplate for four or more fastened-in-place appliances, which excludes cooking equipment, dryers, space heating, air conditioning and EV chargers (220.53). Ranges and cooktops use Table 220.55, which depends on the number and rating of the appliances; enter the demand load from the table¹. The optional method in Part IV isn't covered here.

What this NEC load calculation leaves out

• Kitchen equipment in other than dwelling units (220.56), health care facilities, marinas and farm loads have their own rules in Article 220. Enter those loads at the value the rule gives.¹
• Multioutlet assemblies (220.14(H)) and specific appliances are entered as other loads at their calculated VA.
• The neutral load (220.61) is calculated separately and can differ a lot from the phase load.¹
• The worksheet doesn't balance loads across phases or size conductors. Check ampacity, terminal ratings and voltage drop afterward.
• Local amendments and the edition your jurisdiction enforces win over this page. The full code is readable online at NFPA⁴.

Where the load calculation meets the estimate

The receptacle count in a commercial load calculation comes from the same place as the receptacle count in your bid: the plans. On a design-build job you'll count devices for the electrical takeoff anyway, so the number you enter here should match. After the service and feeders are sized, the voltage drop calculator and the conduit fill calculator check the runs, and the electrical estimate calculator turns the counts into material and labor.

Keep the receptacle and fixture totals on one electrical takeoff sheet and enter them here from that sheet, so a revision that adds outlets changes both numbers at once. Before you price the gear, compare the calculated service size with your own electrical cost per square foot history for the building type; a big gap usually means a load was missed or entered twice.

On a design-build bid, the load calculation is part of what you are selling, so the assumptions behind it belong in the proposal: occupancy, equipment ratings you assumed, and which loads you treated as noncoincident. The guide to bidding electrical jobs covers writing those clarifications. Shops that send design-build takeoffs out instead of doing them in house can compare what electrical estimating services deliver and what they cost.

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