Calculators
Electrical calculators
Free, no sign up, and every assumption written out underneath. Each one uses a published method and names it, so you can check the result instead of trusting it.
Voltage drop
How much voltage a run loses, in volts and percent, plus the smallest conductor that stays inside your limit. Copper or aluminum, single or three phase.
Available fault current
The point to point method. Transformer and conductor run in, fault current at the panel out, with the interrupting rating your equipment needs.
EV charger load check
Whether your service can carry a charger and what breaker it needs, using the demand your house really draws instead of a guess.
EV charging time
How many hours a charge takes, how much range you gain per hour, and what a normal night on the driveway adds.
Circuit load
Whether an appliance overloads the circuit it is plugged into, plus the classic conversion between volts, amps, watts and ohms.
Solar interconnection
The busbar rule for a backfed inverter breaker, and the largest system your panel accepts without being replaced.
Battery runtime
How long a battery carries your load, with depth of discharge and inverter losses taken into account.
Also on the way. A maximum length mode inside the voltage drop calculator, so you can ask it the other question: how far can I go with this conductor and stay inside the limit. After that, wire size with temperature and bundling correction, and the dwelling load calculation.
How to read a result. These calculators are aids, not design documents. They use simplified published methods, they state their assumptions on the page, and they cannot see your installation. Size for ampacity first, then check voltage drop, and confirm anything that matters with your local authority having jurisdiction.
Something missing? Tell me what you calculate by hand every week and I will look at building it.