Introduction
This Electrical Load Calculator tells you how much power your home uses and if your electrical panel can handle more. Enter your home's size, your heating type, and your big appliances. The tool applies NEC (National Electrical Code) rules and shows your total load in VA and amps.
Use it before you add something big, like an EV charger, a hot tub, or a heat pump. You will see if your 100, 150, or 200 amp panel has room left, or if you need a service upgrade.
There are three modes:
- Quick Check: a fast answer in about one minute.
- Full NEC 220 Worksheet: a line-by-line load calculation with demand factors.
- Panel Capacity Checker: see how many amps are left in your panel.
Every result comes with step-by-step math, so you can check the work or show it to your electrician. This tool is for planning only. Always have a licensed electrician confirm the numbers and pull the right permits before any work starts.
How to use our Electrical Load Calculator
Enter your home's size, your main breaker size, and the appliances you use. The calculator shows your total electrical load in VA and amps, the smallest service size the NEC allows, and how much room is left in your panel.
Quick Check
Heated Floor Area: Type the living space you heat and cool. Skip the garage and unfinished basement. Pick ft² or m².
Main Breaker Size: Pick the amp number printed on the biggest breaker in your panel. Choose "I'm not sure" if you can't check it.
Heating & Cooling: Pick the system you have, like a gas furnace with AC, a heat pump, or a mini-split.
Cooking Appliance: Pick electric range or gas range.
Clothes Dryer: Pick electric dryer or gas dryer.
Water Heater: Pick electric tank, electric tankless, or gas.
Small-Appliance Branch Circuits: Enter how many kitchen circuits you have. Code asks for at least 2.
Laundry Branch Circuits: Enter how many laundry circuits you have. Most homes have 1.
Bathroom Exhaust Fans: Enter how many fans are in the home.
HVAC Nameplate VA: Change this number if you know the real rating on your unit's label.
Wall Oven: Pick none, single, or double.
Kitchen Fixed Appliances: Check the boxes for your dishwasher, disposal, and built-in microwave.
Planning to Add: Check any new load you want, like an EV charger, hot tub, pool pump, sauna, or a room addition. The chart and totals update right away.
Full NEC 220 Worksheet
Section A: Enter floor area, small-appliance circuits, and laundry circuits to get your general lighting load.
Section B: Enter bathroom fan count, then check each fixed appliance and type its VA. Use "Add Another Fixed Appliance" for anything else.
Section C: Enter how many HVAC systems you have, then type the VA for each one.
Section D: Pick electric or gas for the range and dryer, add a wall oven, tankless heater, or EV charger, and type their VA.
Section E: Add any other loads, like a well pump, with a name and VA.
Panel Capacity Checker
Panel Size: Pick your panel's amp rating.
System Voltage and Phase: Pick 240 V single phase for most homes. Pick other options for commercial work.
Current Panel Utilization: Pick how full your panel is now. Or list your breakers in the table for a better number.
New Load to Add: Type the amps of the new circuit you want. Leave it blank to just see free space.
New Load Type: Pick continuous if it runs 3 hours or more. The tool then sizes it at 125%.
Equipment Load Builder
Voltage and Phase: Set the supply for the circuit you are building.
Equipment Rows: Name each load, pick continuous or non-continuous, type the watts or kW and the quantity. The tool gives total watts, amps, the smallest breaker, and the smallest wire size.
What Is an Electrical Load Calculation?
An electrical load calculation adds up all the power your home uses. It tells you how many amps your house needs so you can pick the right panel and service size. Electricians do this math before adding a new circuit, upgrading a panel, or wiring a new home. Most building departments ask for it before they give you a permit.
Watts, VA, and Amps
Power is measured in watts or VA (volt-amps). For most home loads, they are close enough to the same thing. Amps tell you how much current flows through a wire. In a normal U.S. home, you find amps by dividing VA by 240 volts. So a 9,600 VA EV charger pulls about 40 amps.
How the NEC Rules Work
The National Electrical Code (NEC) Article 220 sets the rules. It does not make you add every appliance at full power, because you never run everything at once. Instead it uses demand factors:
- 3 VA per square foot for general lighting and outlets (NEC 220.41).
- 1,500 VA for each kitchen small-appliance circuit and each laundry circuit.
- First 3,000 VA at 100%, the next part at 35%, and anything over 120,000 VA at 25% (NEC 220.45).
- 75% demand factor when you have four or more fixed appliances like a dishwasher, disposal, or microwave (NEC 220.53).
- Only the bigger load counts for heating or cooling, never both (NEC 220.51).
- Dryers count at 5,000 VA or nameplate, whichever is larger (NEC 220.54).
- EV chargers count at 7,200 VA or nameplate, whichever is larger (NEC 220.57).
The 80% Rule
A breaker panel should not carry more than 80% of its rating for long periods. A 200-amp panel gives you about 160 usable amps. The other 20% is a safety buffer that keeps wires and breakers from getting hot. Loads that run three hours or more, like EV chargers and electric heat, get sized at 125% for this same reason.
Common Home Service Sizes
Older homes often have 60 or 100 amps. Most homes built today use 200 amps. Large homes with electric heat, a hot tub, or two EV chargers may need 400 amps. If your calculated load is close to your panel size, you likely need a service upgrade before adding anything new.
Signs Your Panel Is Too Small
- Breakers trip often, even when nothing is broken.
- Lights dim when the AC or dryer starts.
- The panel has no open slots left.
- You want to add an EV charger, heat pump, hot tub, or finished basement.
- The panel is a fuse box or an old brand known to fail.
Typical Load Sizes
Here is what common items draw. Always check the nameplate on your own equipment, since real numbers vary.
- Electric range: 8,000 to 12,000 VA
- Electric dryer: 5,000 VA
- Tank water heater: 4,500 VA
- Tankless water heater: 18,000 to 27,000 VA
- Heat pump: 5,000 VA
- Electric furnace: 10,000 to 20,000 VA
- Level 2 EV charger: 7,680 to 14,400 VA
- Hot tub: 8,000 to 12,000 VA
Use this math to plan your project and talk with your electrician. A licensed electrician and your local inspector have the final say, and local codes can be stricter than the NEC.