Takeoff & Estimating — Electrical & Low-Voltage

Panelboard

The breaker enclosure that turns a feeder into branch circuits.

Quick Answer

A panelboard is a wall-mounted enclosure holding a bus and circuit breakers that distributes power from a feeder to branch circuits for lighting, receptacles and equipment. Estimators count each panelboard EA from the one-line diagram and panel schedules, then count the breakers and measure the feeder separately.

The Full Picture

A panelboard takes one feeder in and sends many branch circuits out. Inside the enclosure is a bus, a main breaker or main lugs, and a set of branch breaker spaces. It differs from a switchboard in scale and in how it is built: a panelboard is typically a shallower, wall-mounted assembly in a cabinet, while a switchboard is a larger, floor-standing assembly of sections. Under OSHA's electrical rules, panelboards must be in enclosures made for the purpose, and in most installations they are dead-front.

On the drawings, panelboards show up in three places. The one-line diagram shows each panel's name, voltage, bus rating and the feeder that serves it. The floor plan shows its location, usually in an electrical room or closet. The panel schedule lists every circuit, with breaker size, poles, the load served and a space or spare count. The estimator takes the count of panelboards from the one-line and the schedules and cross-checks that every panel on one has a schedule and a location on the other.

The unit is EA for the panelboard, with the size carried in the description: voltage, phases, bus amperage, main breaker or main lugs, number of spaces and enclosure type. Branch breakers are counted from the schedule by pole count and amperage, since they are priced by type. Feeders to the panel, the conduit and wire for each branch circuit, and any surge protection or sub-feed breaker at the source are carried on separate lines. The specifications, under Division 26, set the manufacturer, enclosure rating and any required features such as ground-fault protection on certain breakers.

Panel placement is not just a drawing detail, because code and safety rules give it a physical footprint. OSHA's rules put switchboards and panelboards in dedicated spaces from the floor to 6 ft above the equipment or the structural ceiling, whichever is lower, which affects what else can be drawn above them. A frequent estimating miss is to count the panel but not the housekeeping pad, the backboard or the extra feeder length that a relocated electrical room causes.

Real Examples

→Worked takeoff: panelboards on a three-story building: The one-line shows one lighting panel (LP) and one receptacle panel (RP) on each of 3 floors, plus an emergency panel EM-1 in the basement. Panelboards are 3 + 3 + 1 = 7 EA. The estimator checks that the schedule sheet contains 7 schedules and that all 7 appear on the plans before pricing.

→Breakers from the schedule: LP-1's schedule lists 24 single-pole 20 A breakers and 3 two-pole 30 A breakers. Those are carried as 24 EA and 3 EA on separate lines, because the pole count changes the unit price, even though the panelboard itself is one EA.

→Mismatch between one-line and plans: The one-line shows a panel RP-2, but the floor plans label the same location RP-3. The estimator flags it for an RFI before the count is final, since a missing or duplicate panel changes the feeder and breaker quantities.

Common Misconceptions

People assume: A panelboard and a switchboard are the same thing at different sizes.

Actually: Both distribute power, but a switchboard is a larger, usually floor-standing, assembly that typically sits near the service, while panelboards hang on walls further down the distribution. They are counted and specified separately.

People assume: Pricing the panelboard includes its breakers.

Actually: The enclosure and bus are one item and the branch breakers are another. Panel schedules give the breaker mix, and it is easy to omit them when only the panel count is carried.

Does MeltPlan Solve This?

Partially — adjacent

Counting panelboards and their branch breakers from one-line diagrams and panel schedules is takeoff work. MeltPlan's takeoff service uses AI to pull quantities from PDF plans, and US-based experienced estimators review and adjust them. Setting bus ratings, deciding spare capacity and pricing the equipment remains your estimating team's work.

Get panelboard and breaker counts from your electrical plans →

Frequently Asked Questions

What is a panelboard used for?

A panelboard distributes power from a feeder to branch circuits through circuit breakers, serving lighting, receptacles and equipment in a section of a building.

What unit is a panelboard taken off in?

Each panelboard is counted EA. Branch breakers are counted EA from the panel schedule, and feeder and branch wiring are measured in LF.

Where do I find panelboards on the drawings?

Look at the one-line diagram for the panel name and feeder, the electrical floor plans for its location, and the panel schedule sheets for each circuit.

Does a panelboard need clear space around it?

Yes. OSHA's rule sets working space width at the equipment width or 30 in, whichever is greater, per 29 CFR 1910.303(g), and the local electrical code adds its own requirements.