Frequently asked questions
Why is the calculated load lower than my breakers add up to?
Breakers are sized to protect wires, not to describe what runs at once. The NEC® load calculation starts from floor area, kitchen and laundry circuits and appliance nameplates, then applies demand factors.
Where do I find my service size?
On the handle of the main breaker, usually the large breaker at the top of the panel or next to the meter outside. The label inside the door shows the panel rating, which can be higher.
How accurate is this estimate?
It follows the NEC® 220.83 method with the numbers you enter. Defaults stand in for unknown nameplates, so treat it as an estimate; a licensed electrician and your inspector make the final call.
What do green, yellow and red mean?
Green means the calculated demand is up to 80% of your service, yellow 80–100%, red over 100%. The 80% line is our margin for future loads, not a code rule.
Does the NEC edition change my result?
It can. The 2026 edition moves this method to 120.83 and counts some new loads differently. We use NEC® 2023 by default; your building department can tell you which edition your permit follows.
Do I need a permit to add a large appliance?
Usually, yes — new 240 V circuits for heat pumps, EV chargers, ranges and hot tubs typically need an electrical permit, and inspectors often ask for a load calculation.
Do you store my data?
No. The calculation runs in your browser. Results live in the link itself (after the #), which browsers never send to a server.
Does a heat pump replace my air conditioner in the calculation?
Yes, in our tool a new heat pump takes over from an existing central AC or heat pump, since one system does both jobs. Electric backup heat strips still count separately.
What size breaker does a heat pump need?
Whatever the outdoor unit’s nameplate says: the MCA sets the wire size and the MOCP is the largest breaker allowed. Tonnage alone isn’t enough to know.
How is an EV charger counted in the load calculation?
Under NEC® 2023 220.57 at 7,200 VA or the charger’s nameplate, whichever is higher. A 40 A charger counts as 9,600 VA.
Can a load management device avoid a panel upgrade?
Often. A listed energy management system pauses or slows the charger when the house is busy, and NEC® 2023 lets the calculation use its setpoint instead of the full load.
Does an induction range use more power than an electric range?
For the load calculation they’re treated the same: by nameplate, or 12,000 VA by default. Replacing an electric range with induction usually changes little; replacing gas adds a new load.
Can I get induction without a 240 V circuit?
Some 120 V induction ranges with built-in batteries exist and plug into a standard outlet. Check the manufacturer’s circuit requirements before you buy.
Should I pick a 120 V or 240 V heat pump water heater?
A 120 V unit plugs into an outlet and adds little load, but recovers slower. A 240 V hybrid recovers faster and counts like a 4,500 VA electric water heater.
How much power does a hot tub add?
Most 240 V spas are on a 40–50 A circuit; we count 7,200 VA when the nameplate is unknown. Heater and pumps vary widely, so check the spec sheet.
Still unsure? Run the free check or read the guides.