Electrical Load and Wire Sizing Calculation Report

Voltage drop is calculated by multiplying the wire resistance by the current and the length of the run. For a single-phase circuit, you multiply two by the material resistivity, the current in amperes, and the one-way distance, then divide by the circular mil area of the conductor. Keeping this total drop under 3% for branch circuits prevents equipment damage and energy waste.

Aluminum has higher electrical resistance than copper, meaning it requires a larger wire gauge to safely carry the same amount of current. For example, a 100-amp service typically requires a #3 AWG copper wire but requires a larger #1 AWG aluminum wire. You must also use terminals specifically rated for aluminum to prevent oxidation and fire hazards.

The National Electrical Code limits conduit fill to 40% of its internal cross-sectional area when routing three or more conductors to prevent dangerous heat buildup. If you are pulling only two wires, the maximum fill limit is 31%, and for a single wire, it is 53%. You must calculate the total outer area of all your specific wires combined to select the correct conduit trade size.

Adding up individual breaker sizes results in an oversized, unnecessarily expensive electrical service because not all appliances run at maximum capacity simultaneously. Applying code-approved demand factors scales the service size down to reflect actual real-world peak usage patterns. This ensures your system is safe and fully compliant without wasting thousands of dollars on oversized panels and heavy-gauge conductors.