Electrical Load Calculator (Panel Size & Amps)
Enter the home’s square footage and its major fixed loads to estimate the total calculated load, the resulting amperage, and a recommended panel size using the standard (simplified) dwelling load method. The math updates as you type.
Electrical Load Calculator
Enter square footage and appliance loads in VA (volt-amps). Defaults reflect a typical single-family home.
Educational estimate only. This uses the standard (simplified) dwelling load calculation method and is not a substitute for a licensed electrician’s load calculation, NEC Article 220 compliance review, or approval from your local Authority Having Jurisdiction (AHJ). Always have panel upgrades and service sizing verified and permitted by a licensed electrician.
How the load calculation works
Dwelling load calculations start with a general lighting and receptacle load based on square footage, plus small-appliance and laundry circuits, then apply a demand factor because not every circuit runs at once. Fixed appliances and HVAC are added on top at full (or largest-of) value.
| Step | Example: 2,000 sq ft home |
|---|---|
| General load (sq ft × 3 + circuits × 1500 VA) | 2000×3 + 3×1500 = 10,500 VA |
| Demand factor (first 3,000 VA at 100%, rest at 35%) | 3,000 + (7,500×0.35) = 5,625 VA |
| + Fixed appliances (water heater, dryer, range, other) | 4,500+5,000+8,000+1,200 = 18,700 VA |
| + Larger of AC or heat | +3,600 VA |
| Total VA ÷ 240V | 27,925 ÷ 240 = 116.4 amps → 150A panel |
Panels are sized in standard steps — 100A, 150A, 200A — and it is normal practice to size up rather than run at the edge of a panel’s rating, especially with EV chargers or future additions in mind.
Contractor Estimate Calculator (Excel & Google Sheets)
Turn the load calc into a priced, itemized estimate — panel, breakers, labor, and markup, auto-totaled. The estimate you hand the client after the load calculator tells you the service size.
When to upsize the panel
If the calculated amperage lands near or over a panel’s rating (80A on a 100A panel, 120A on a 150A panel), upsizing is usually cheaper done once than twice. EV chargers, hot tubs, workshops, and heat-pump conversions all add meaningful load — account for planned additions before the calculated amps push you to the ceiling.
Once the panel is sized, send a clean invoice
The calculator gives you the load and panel size; your bid turns it into a price. When the job is done, bill it with an itemized electrical invoice that separates panel, breakers, and labor — and quote new work from an electrical estimate template so your margin is in the number before you ever open the panel.
Frequently asked questions
Is this a substitute for a licensed electrician’s load calculation?
No. This calculator uses the standard simplified dwelling load method for educational estimating only. A licensed electrician must perform the official NEC Article 220 load calculation and file it with your local Authority Having Jurisdiction (AHJ) before any panel upgrade or new service is approved.
What panel size do most homes need?
Most modern single-family homes land on a 150A or 200A panel. Smaller homes with gas heat and gas water heating sometimes get by on 100A, while larger homes, electric heat, or EV charging usually push toward 200A or larger.
Why isn’t AC load just added to heat load?
Air conditioning and electric heat are not used at the same time, so the standard method only counts the larger of the two rather than adding both.
Is this electrical load calculator free?
Yes — free, no sign-up. Enter square footage and appliance loads and read the estimated amps and recommended panel size. Estimates only; confirm with a licensed electrician.