Electrical Panel Calculator

Calculate total circuit load and determine if your panel needs an upgrade.

By Konstantin Iakovlev · Updated April 2026 · Source: HomeAdvisor

Total Amps

420A

Panel Size Needed

200A

Panel Analysis

Total Circuit Amps420A
Derated Load (80%)336A
Recommended Panel200-Amp
Estimated Upgrade Cost$2,500 - $4,500

Use the Electrical Panel Calculator above to calculate your results. Enter your values and see instant results — all calculations run in your browser.

Disclaimer: This calculator is for informational purposes only and does not constitute tax, financial, or legal advice. Results are estimates based on the information you provide and current rates. Always consult a qualified tax professional or financial advisor for advice specific to your situation.

How It Works

Knowing whether your service panel can carry everything your home draws is a safety question as much as a planning one. The tool totals your household electrical load and checks it against your existing panel's capacity. As electric vehicles and smart-home devices push demand higher, that capacity check has become essential in 2026.

The calculation adds up the continuous load (such as HVAC and the water heater) and the non-continuous load (such as lighting and small appliances) across each circuit. A diversity factor, typically 0.8 for residential panels, is then applied to the total non-continuous load because not every device runs at once.

Final panel assessments and upgrades belong in the hands of a licensed electrician, so treat these numbers as a starting point for that conversation. Where people most often go wrong is underestimating future demand, particularly the heavy dedicated circuits new EV chargers need, for example 50A for Level 2 charging.

Example: Home with EV Charger

  1. 1 Enter the amperage and voltage for each major appliance (e.g., Electric Range: 50A/240V, Central AC: 30A/240V, EV Charger: 40A/240V). Also, input the number of general-purpose 15A and 20A circuits.
  2. 2 The calculator sums the wattage for all continuous loads (e.g., AC, EV charger) and non-continuous loads (e.g., lights, outlets). It then applies the diversity factor to the non-continuous load and adds it to the continuous load to get the total estimated peak demand in Amps at your service voltage.
  3. 3 Based on your inputs, the calculator determines your total estimated electrical load is 175 Amps. If your current panel is 150 Amps, the result will indicate your panel is undersized and an upgrade is recommended.
  4. 4 A 175 Amp load on a 150 Amp panel poses a significant risk of tripping breakers and potential electrical hazards. Upgrading to a 200 Amp or 225 Amp panel would provide sufficient capacity for your current needs and future expansions like additional EV charging or solar integration.

Source: HomeAdvisor · Last updated: April 2026

Frequently Asked Questions

How do I know if my electrical panel needs an upgrade?
Signs include frequent breaker trips, flickering lights, warm or discolored panel, a fuse box instead of breakers, or a panel with less than 200 amps. If you are adding an EV charger, hot tub, or major addition, you likely need a panel upgrade.
How much does an electrical panel upgrade cost?
Upgrading from 100 to 200 amps typically costs $1,500-$4,000 including permits and inspection. A 400-amp upgrade runs $4,000-$8,000. Costs vary by region and whether the utility needs to upgrade the service drop to your home.
How do I calculate my total electrical load?
Add up the wattage of all circuits and major appliances. Use the NEC load calculation: 3 watts per square foot of living space for general lighting and receptacles, plus nameplate ratings for major appliances like the range, dryer, A/C, and water heater.

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