Six questions. Same NEC Article 220 math a licensed electrician uses — just with typical Wake County defaults filled in. Refine any number in the full worksheet below.
Tap anything you're planning. Each one is counted at its nameplate rating (NEC 220.14 / 220.57) and added to the result above in real time.
Pre-filled from your quick check. Edit any line — the result band follows the worksheet once you change something here.
Two service sizes come out of the calculator. Here is why they differ, and what to do if you land in the red.
NEC Article 220 adds up your general lighting and receptacle load, applies demand factors (100% of the first 3,000 VA, 35% of the rest; 75% on fixed appliances when you have four or more), then adds heating, cooling and major appliances at nameplate. Divide by 240 V and round up to the next standard size — 100, 150, 200 or 400 A. That is the minimum an inspector will accept.
We add 25% headroom to the calculated amps before picking a size. It is not a code rule — it is what keeps the next project (a second EV, a heat-pump water heater, a finished attic) from turning into a second service upgrade. If the two figures match, you are in good shape either way.
Why guessing is expensive. An overloaded service does not just trip breakers. It is one of the most common reasons an EV charger or hot tub permit gets flagged at inspection — after the hardware is bought and the wire is pulled. A calculation first costs nothing; a re-do costs a second visit and a second permit.
Typical nameplate values we see in Wake County homes. Your equipment’s label wins — type the exact figure into the full worksheet if you have it.
| Project | Typical rating | Adds to calculated load | Worth knowing |
|---|---|---|---|
| Level 2 EV charger | 32–60 A | 7,680–14,400 VA (32–60 A) | NEC 220.57 counts the charger at 7,200 VA or nameplate, whichever is larger. A 48 A charger is the most common install; Duke Energy’s credit covers the circuit work. |
| Hot tub / spa | 40–60 A | 9,600–14,400 VA | Heater plus pumps on one GFCI-protected circuit. Most 6-person tubs are 50 A. |
| Electric tankless water heater | 18–36 kW | 18,000–36,000 VA (75–150 A) | The single biggest load you can add to a house. A 27 kW unit alone is 112 A — it pushes most 200 A homes over. |
| Whole-home standby generator | — | 0 VA | A generator does not add load; it is sized from this calculation. Use the number here on our generator page. |
| Pool pump | 1–2 HP | 1,500–2,800 VA | Variable-speed pumps draw far less most of the day but are still counted at nameplate. |
| Pool heat pump / electric pool heater | 25 A / 18 kW | 6,000 / 18,000 VA | A resistance pool heater is the second-biggest residential load after tankless water heating. |
| Sauna | 6–9 kW | 6,000–9,000 VA | Usually a dedicated 40 A circuit. |
| Mini-split / second HVAC | 15–30 A | 3,600–7,200 VA | Counted at nameplate alongside your main system. |
| Finished basement / addition | 500 sq ft | 1,500 VA gross, ~525 VA after demand factor | Square footage is cheap on the calculation; the kitchenette, mini-split and bathroom heater in it are not. |
| Switching gas range / dryer to electric | 40 A / 30 A | 8,000 / 5,000 VA | Induction ranges are counted the same as conventional electric. |
Values are typical nameplate ratings for planning, not a substitute for the label on your equipment. VA at 240 V: amps × 240.
Most Level 2 home EV chargers draw between 7,200 and 11,500 VA (30–48 amps at 240V) continuously (3hrs or more). If your panel is already near its rated capacity from existing lighting, HVAC, and appliances, adding a charger can push you over the limit — that’s exactly what this calculator estimates before you buy the hardware.
It depends on your home’s total calculated load, not just the number of devices. Many mid-size Wake County homes run fine on a 100A panel, but homes adding several large loads at once — a generator, an EV charger, and an electric range, for example — often need 150A or 200A service. Run your specifics through the calculator above for a personalized estimate.
It follows the standard method in NEC Article 220 — the same load-calculation approach licensed electricians use, including demand factors for general lighting and fixed appliances. It’s built for planning purposes; a licensed electrician still verifies the final numbers before any permit is filed.
A few, depending on your situation: a full on-site load calculation and panel upgrade (commonly to 150A or 200A), adding a subpanel, or a load-management device for the new equipment. ARC Electric provides a free in-home quote with no trip charge to work out which one fits.
If your calculated load is at or near your panel’s limit, don’t find out the hard way. A licensed ARC electrician comes out, reads the nameplates, runs the calculation you just ran with exact figures, and gives you a firm flat-rate price on whatever it turns out you need — or tells you that you need nothing.
Mon–Fri 8:00–5:00 · NC Licensed & Insured #29565 · Serving Raleigh, Cary, Apex, Holly Springs, Fuquay-Varina and all of Wake County.
Tell us what you’re planning to add and we’ll get back to you.