What size electrical panel do I need for my house?

Most modern homes need a 200-amp electrical panel. To determine the exact size, calculate your total electrical load using the NEC 220 Standard Method: multiply square footage by 3 VA, add small appliance and laundry circuit loads, apply demand factors, then add all major appliance loads. Divide the total by 240V to get the required amperage, and select the next standard panel size above that number (100A, 125A, 150A, 200A, or 400A). Homes under 1,500 sq ft with gas appliances may get by with 100A, while large homes with EV chargers, heat pumps, and electric ranges often need 200A or 400A service.

How do you calculate electrical load for a house?

Calculate residential electrical load using the NEC Article 220 Standard Method. First, multiply the living area square footage by 3 VA per square foot for general lighting (NEC 220.12). Add 1,500 VA for each small appliance circuit (minimum 2) and each laundry circuit (minimum 1). Apply NEC Table 220.42 demand factors: first 3,000 VA at 100%, remainder at 35%. Then add all major appliance nameplate loads, applying a 75% demand factor if you have 4 or more appliances (NEC 220.53). The total divided by 240V gives your service amperage.

What wire gauge do I need for a 200 amp service?

A 200-amp residential service requires 2/0 AWG copper conductors or 4/0 AWG aluminum conductors per NEC Table 310.16. The service entrance cable typically includes two hot conductors, one neutral, and one ground. For underground service (USE cable), the same wire sizes apply. The grounding electrode conductor for 200A service must be at least 4 AWG copper per NEC Table 250.66. Always verify with your local utility and building department, as some jurisdictions have additional requirements.

What is the NEC demand factor for residential loads?

The NEC demand factor for residential general lighting and receptacle loads is defined in Table 220.42: the first 3,000 VA at 100% and the remainder at 35%. This means a home with 12,000 VA of general load would have a demand-adjusted load of 3,000 + (9,000 × 0.35) = 6,150 VA. For fastened-in-place appliances, NEC 220.53 allows a 75% demand factor when you have 4 or more qualifying appliances. These demand factors recognize that not all loads operate simultaneously.

How many circuits can a 200 amp panel handle?

A 200-amp panel can physically hold 30 to 42 circuit breaker spaces depending on the model, but the total connected load on all circuits combined must not exceed the panel rating when demand factors are applied. In practice, a 200A panel can comfortably serve a 3,000+ sq ft home with central A/C, electric range, dryer, water heater, and multiple general circuits. The NEC demand factor calculations ensure that even when the sum of all breaker ratings exceeds 200A, the actual simultaneous load stays within the panel’s capacity.

What is the difference between 100 amp and 200 amp service?

A 100-amp service provides up to 24,000 watts (100A × 240V) of simultaneous power, while a 200-amp service provides up to 48,000 watts. A 100A panel is adequate for small homes under 1,500 sq ft with gas heating and cooking, but most modern homes require 200A to handle electric ranges, dryers, central A/C, and modern electronics. If you plan to add an EV charger (40A circuit), heat pump, or hot tub, you almost certainly need at least 200A service. Upgrading from 100A to 200A typically costs $1,500–$3,000 installed.

Do I need a permit to upgrade my electrical panel?

Yes, an electrical panel upgrade requires a permit in virtually all jurisdictions. The work must be performed by a licensed electrician and inspected by the local building department. The permit process ensures the installation meets NEC requirements and local code amendments. Your utility company must also be notified to disconnect and reconnect service. Unpermitted electrical work can void your homeowner’s insurance, create safety hazards, and cause problems when selling your home.

Electrical Load Calculator — Panel Size & Wire Gauge

How to Use the Electrical Load Calculator

How to Calculate Residential Electrical Load

Calculating your home's electrical load is the first step in determining the right panel size and service entrance capacity. The National Electrical Code (NEC) Article 220 provides a standard method for residential load calculations that electricians, inspectors, and homeowners can follow. This electrical load calculator implements the NEC 220 Standard Method, giving you an accurate estimate of your total service load in volt-amperes (VA), recommended panel size, and wire gauge requirements for each circuit. While this tool provides professional-grade estimates, always consult a licensed electrician before making changes to your electrical system.

Step 1: General Lighting Load (NEC 220.12)

The NEC assigns a unit load of 3 VA per square foot of living area for general lighting and general-use receptacles. This covers all permanently installed lighting fixtures, plug-in lamps, and standard convenience outlets throughout the home. Simply multiply your total finished living area (in square feet) by 3 to get the general lighting load in VA. For a 2,000 sq ft home, that's 2,000 × 3 = 6,000 VA of general lighting load.

Step 2: Small Appliance and Laundry Circuits (NEC 220.52)

The NEC requires a minimum of two 20-amp small appliance circuits for kitchen, dining, and pantry areas (NEC 220.52(A)), and at least one 20-amp laundry circuit (NEC 220.52(B)). Each circuit is rated at 1,500 VA for load calculation purposes, regardless of actual connected load. Two small appliance circuits contribute 3,000 VA, and one laundry circuit adds 1,500 VA to the total general load.

Step 3: Apply Demand Factors (NEC Table 220.42)

Not all lights and receptacles run simultaneously, so the NEC applies demand factors to reduce the calculated load to a realistic level. For residential lighting and receptacle loads, NEC Table 220.42 specifies: the first 3,000 VA at 100% and the remainder at 35%. For a home with 10,500 VA of total general load, the demand-adjusted load is 3,000 + (7,500 × 0.35) = 5,625 VA. This demand factor significantly reduces the apparent load, which is why a 200A panel can serve a home with far more than 200A of connected circuits.

Step 4: Add Major Appliance Loads

Major appliances — electric range, dryer, water heater, central A/C, heat pump, EV charger — are added at their nameplate rating in watts. Each gets its own dedicated circuit with the appropriate breaker size and wire gauge. If you have four or more fastened-in-place appliances (other than ranges, dryers, A/C, and space heating), NEC 220.53 allows a 75% demand factor on the combined appliance load. This reflects the statistical improbability of all appliances running at full load simultaneously.

Step 5: Determine Panel Size and Wire Gauge

The total service load (demand-adjusted general load + appliance loads) divided by the 240V service voltage gives the required service amperage. The recommended panel size is the next standard panel rating above the calculated amps: 100A, 125A, 150A, 200A, or 400A. Most new construction uses 200A panels as the baseline. The service entrance wire gauge is determined by NEC Table 310.16 based on the panel amperage — for example, 200A service requires 2/0 AWG copper conductors. Each branch circuit also has specific wire gauge requirements based on its breaker size: 15A circuits use 14 AWG, 20A use 12 AWG, 30A use 10 AWG, and so on.

When to Upgrade Your Electrical Panel

Consider upgrading your panel if your calculated load approaches or exceeds your current panel's capacity, if you're adding major appliances (especially EV chargers, heat pumps, or hot tubs), if your panel uses obsolete breaker types (Federal Pacific, Zinsco), or if you notice frequent breaker trips. A panel upgrade from 100A to 200A typically costs $1,500 to $3,000 installed by a licensed electrician, and it's one of the best investments for both safety and home value.

Disclaimer: This calculator provides estimates based on NEC standard methods for educational and planning purposes. Actual electrical work must be performed by a licensed electrician and comply with all local codes and regulations. Always obtain required permits before modifying your electrical system.

Free Electrical Load Calculator — Panel Size & Wire Gauge