Changelog

Every correction that changes a calculated result is listed here with what was affected, so a result you saved earlier can be re-checked. Found something wrong? Use the error report form — each fix ships with a test that cites its source.

1. 2026-10-26CorrectionVoltage Drop, Cable Sizing

   NEC voltage drop at power factors other than 1.0 and 0.85

   Effective impedance was linearly interpolated between the Table 9 1.0-PF and 0.85-PF columns, and held at the 0.85 value below 0.85. It is now R cosθ + X sinθ (Table 9 Note 2); below 0.85 the result is never lower than the 0.85 column. Found by re-running a published example: 500 kcmil copper at 0.9 PF gave 4.50 V instead of 4.92 V.

   Who was affected: NEC mode at PF other than exactly 1.0 or 0.85. Between 0.85 and 1.0, large conductors were understated: 4/0 copper by up to 10 %, 500 kcmil by up to 20 % and 1000 kcmil by up to 29 % (worst near 0.97 PF); 4 AWG and smaller by about 3 % or less. Below 0.85, copper 250 kcmil and larger (aluminum 400 kcmil and larger) were understated by up to 24 % at 0.5 PF; smaller sizes are unchanged. The voltage-drop check in Cable Sizing uses the same calculation, so a recommended size may now be larger.

2. 2026-10-12ClarificationVoltage Drop, Cable Sizing

   Impedance data is the steel-conduit column

   The assumptions said PVC conduit, but the data has always been Table 9’s steel-conduit column. The text now says steel (the conservative case). Numbers did not change.

3. 2026-10-12AddedVoltage Drop, Cable Sizing

   347 V single-phase and 600 V three-phase systems

   Canadian 600Y/347 V systems can be selected. Conductor data is still NEC Table 9 / 310.16, not the Canadian Electrical Code.

4. 2026-10-11CorrectionVoltage Drop

   Single-phase conductor loss counted three conductors

   Single-phase systems were tagged as three-phase in the loss calculation, so the watts lost were 50 % too high (for example 222 W instead of 152 W). DC resistance for 14 – 8 AWG copper and 12 – 8 AWG aluminum now uses Table 8 stranded values.

   Who was affected: The “conductor loss” figure for single-phase systems. The voltage drop itself was not affected.

5. 2026-10-11AddedElectrical Load

   EV charger as its own input

   EVSE is entered separately at the larger of 7,200 VA or nameplate (220.57), with a choice between the 220.82 general load (default) and 100 % where the AHJ requires it. The rule used is shown with the result.

6. 2026-10-09AddedAll

   Cable Sizing, Electrical Load, Power Factor and Transformer calculators

   Four calculators added alongside Voltage Drop, each with a basis line, shareable link and FAQ.

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