Electrical & Solar Tools
Wire sizing, voltage drop and solar planning, with the code rules that decide the answer.
AWG size from load, distance and voltage using the NEC ampacity tables — including the termination rule that makes the 90 °C column the wrong answer.
Three-Phase Power CalculatorkW, kVA, kVAR and amps for three-phase or single-phase, with power factor correction and the line-to-line voltage trap made explicit.
Solar Panel and Array Size CalculatorTurn your monthly kWh into an array size, panel count and roof area, using real peak sun hours and a loss stack that compounds properly.
Conduit Fill and Box Fill CalculatorNEC Chapter 9 conduit fill and 314.16 box fill, including Note 7 rounding and the separate ampacity derate that fill alone never warns you about.
Home Battery Backup Runtime CalculatorHow long a home battery really lasts, using appliance duty cycles rather than nameplates — plus the surge check that decides whether it stays up at all.
Electrical Service Load CalculatorWhat size service a house needs, worked both NEC ways side by side — because the standard and optional methods are both legal and disagree.
Transformer kVA Sizing CalculatorTransformer size, primary and secondary current, NEC 450.3(B) protection and the available fault current that decides every rating downstream.
Motor Circuit and Breaker CalculatorNEC 430 motor full-load current, conductor size, breaker or fuse and overload setting — with the table-not-nameplate rule made unmissable.
Solar Payback and Net Metering CalculatorWhat solar actually saves you, worked separately for retail net metering, net billing and no export credit — because the tariff decides more than the sun.
Solar Panel Tilt and Azimuth CalculatorWhat your roof angle and bearing actually cost you — usually far less than people fear — with magnetic declination handled properly.
EV Charger Circuit and Charge Time CalculatorCharge time, circuit size and cost for a home EV charger — including the onboard charger limit that usually decides your speed, not the wall unit.
Appliance Energy Cost CalculatorWhat each appliance really costs you per year, ranked — and why phantom load is a fraction of what the folklore claims.
Generator and Transfer Switch SizingWhat size generator your house actually needs — sized on starting watts, derated for altitude and heat, with the backfeeding warning it deserves.
Room Wiring Requirements GuideReceptacle spacing, required circuits, GFCI and AFCI by room and code edition — with the difference between the two protections made plain.
Panel Schedule and Phase BalancerLay out a load centre and balance the legs — with the slot pattern and the per-leg capacity rule that most people have backwards.
About these electrical & solar tools
The single most common error in wire sizing is reading the 90 degree column. Almost all modern building wire is rated 90 degrees Celsius and that column of NEC Table 310.16 gives generous ampacities, but NEC 110.14(C) limits you to the temperature rating of the terminations, and breakers, panels and receptacles rated 100 amps or less are 60 degrees unless the equipment is specifically marked otherwise. Most residential equipment is not. The 90 degree column exists so there is a starting point to derate from when correcting for ambient heat or for bundling several conductors in one raceway, and those corrections multiply rather than compete: six conductors in a hot attic can leave you 70 per cent of the table figure. Two further rules catch people regularly. Conductors of 14, 12 and 10 AWG carry a hard overcurrent cap of 15, 20 and 30 amps under NEC 240.4(D) whatever the ampacity table says, and continuous loads — anything running three hours or more, which includes EV chargers and most lighting — are sized at 125 per cent, which is why a 48 amp charger needs a 60 amp circuit. Voltage drop, by contrast, is not enforceable at all: it appears only as an informational note recommending 3 per cent on a branch circuit and 5 per cent overall. It is nonetheless what decides the conductor on any long run, because a circuit can be entirely legal and still leave a motor stalling. Everything here is a planning aid; local amendments, the equipment listing and the inspector govern.