Electrical Panel Load Calculator
Calculate your home's total electrical panel load and remaining capacity in volt-amperes, so you know whether your panel can support new appliances, an EV charger, or a home addition. Use it before calling an electrician for a panel upgrade assessment.
About this calculator
A residential electrical panel's total capacity equals its amp rating multiplied by the system voltage (240 V in North America), giving capacity in volt-amperes (VA). The actual load is calculated by summing general lighting and outlet loads, appliance loads, and HVAC loads, then multiplying by a demand factor. The demand factor (typically 0.75–1.0) recognizes that not all circuits operate simultaneously at full load—the NEC allows reduced demand factors for certain load categories. Subtracting actual load from panel capacity gives the available headroom. Formula: Available Capacity (VA) = panel_rating × 240 − (general_lighting + appliance_loads + hvac_loads) × demand_factor. A positive result means spare capacity; a negative result means the panel is overloaded.
How to use
Example: 200 A panel, general lighting = 5,000 VA, appliances = 8,000 VA, HVAC = 6,000 VA, demand factor = 0.80. Step 1 — Panel capacity: 200 × 240 = 48,000 VA. Step 2 — Total connected load: 5,000 + 8,000 + 6,000 = 19,000 VA. Step 3 — Apply demand factor: 19,000 × 0.80 = 15,200 VA. Step 4 — Available capacity: 48,000 − 15,200 = 32,800 VA. This panel has 32,800 VA (~136 A) of remaining capacity for new loads.
Frequently asked questions
How do I know if my electrical panel needs an upgrade?
Signs that an upgrade may be needed include frequently tripping breakers, flickering lights when large appliances start, a panel rated below 100 A (common in older homes), or available capacity near zero on this calculator. Adding a major load like an EV charger (typically 7,200–11,500 W) or central AC unit requires confirming sufficient headroom exists. A licensed electrician should perform a formal load calculation per NEC Article 220 before any upgrade, but this calculator gives you a reliable preliminary estimate.
What is a demand factor and how is it used in electrical load calculations?
A demand factor reflects the statistical reality that not every electrical load in a building operates at full capacity simultaneously. The NEC assigns specific demand factors to load categories—for example, the first 3,000 VA of lighting is taken at 100%, the next 117,000 VA at 35%. Using a blended demand factor between 0.75 and 1.0 for residential calculations prevents over-sizing panels while maintaining safety. A demand factor of 1.0 is the most conservative and is used when loads are expected to run simultaneously, such as in commercial kitchens.
What size electrical panel does a modern home need?
Most modern homes require a minimum 200 A service panel, providing 48,000 VA of capacity at 240 V. Homes with electric vehicles, electric dryers, electric ranges, electric water heaters, and central HVAC may need 320 A or even 400 A service as electrification increases. Older homes built before 1970 often have only 60–100 A panels, which are typically insufficient for today's loads and may be uninsurable. Use this calculator to assess your current load and compare it to your panel's rated capacity to determine whether an upgrade is warranted.