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Dwelling Load Calculator
Run a standard NEC Article 220 dwelling load calculation to size a residential service.
Recommended service
150 Aat 240 V
Calculated load is 35,950 VA, or 149.8 A.
- Total calculated loadAfter all Article 220 demand factors
- 35,950 VA
- Calculated currentTotal VA ÷ 240 V
- 149.8 A
- Load on your existing service100 A service
- 150%
- Headroom at the recommended sizeSpare capacity for future load
- 0.2 A
A 100 A service is not adequate
The calculated load of 149.8 A exceeds a 100 A service, and the standard method points to 150 A. Before committing to an upgrade, price the Article 220 Part IV optional method — it frequently yields a smaller calculated load — and look at load management under NEC 625.42 and Article 750, which can shed EV or water heater load rather than force a service change.
Non-coincident loads handled
Heating at 10,000 VA and cooling at 5,000 VA cannot run together, so NEC 220.60 counts only the larger — 10,000 VA from electric heating.
| Load | Code basis | Connected VA | Demand factor | Calculated VA |
|---|---|---|---|---|
| General lighting group after demand factors | Table 220.45 — 100 / 35 / 25% | 10,500 | 53.6% net | 5,625 |
| Electric range | Table 220.55 Column C | 12,000 | 67% | 8,000 |
| Electric clothes dryer | 220.54 — 5,000 VA minimum | 5,000 | 100% | 5,000 |
| Water heater | 220.53 — fastened in place | 4,500 | 75% | 3,375 |
| Dishwasher | 220.53 — fastened in place | 1,200 | 75% | 900 |
| Disposal | 220.53 — fastened in place | 900 | 75% | 675 |
| Built-in microwave | 220.53 — fastened in place | 1,500 | 75% | 1,125 |
| Larger of heating or cooling — electric heating | 220.60 — non-coincident loads | 15,000 | Larger only | 10,000 |
| Largest motor, additional 25% | 220.50 with 430.24 | 5,000 | 25% | 1,250 |
| Total calculated load | 35,950 VA |
| Component | Code basis | Calculation | VA |
|---|---|---|---|
| General lighting and receptacles | 220.41 — 3 VA/ft² | 2,000 ft² × 3 | 6,000 |
| Small-appliance circuits (2) | 220.52(A) — 1,500 VA each | 2 × 1,500 | 3,000 |
| Laundry branch circuit | 220.52(B) — 1,500 VA | 1 × 1,500 | 1,500 |
| First 3,000 VA | Table 220.45 demand factor | 3,000 VA × 100% | 3,000 |
| 3,001 through 120,000 VA | Table 220.45 demand factor | 7,500 VA × 35% | 2,625 |
| General lighting group, calculated | 10,500 VA connected | 5,625 VA |
| Service size | Capacity at 240 V | Load on service | Status |
|---|---|---|---|
| 100 A | 24,000 VA | 150% | Undersized |
| 125 A | 30,000 VA | 120% | Undersized |
| 150 A | 36,000 VA | 100% | Recommended |
| 200 A | 48,000 VA | 75% | Adequate |
| 225 A | 54,000 VA | 67% | Adequate |
| 400 A | 96,000 VA | 37% | Adequate |
What this assumes
- Uses the NEC Article 220 Part III standard method for a single dwelling unit.
- General lighting load is 3 VA per square foot of habitable area, with Table 220.45 demand factors applied.
- The larger of heating or cooling is counted, per NEC 220.60, since they do not run simultaneously.
Important
A service upgrade requires a permit, a utility coordination appointment and an inspection everywhere in the United States. Use this to understand the scope before you call — not to perform the work.
Understanding the result
Why 100 amps is often not enough anymore
A 100A service was sized for a house with gas heat, gas cooking and no air conditioning. Add a heat pump, an induction range, a heat pump water heater and a Level 2 EV charger and the calculated load routinely exceeds 100A, which is why panel upgrades have become one of the most common residential electrical jobs.
Standard method versus optional method
Article 220 Part III is the standard method used here. Part IV offers an optional method for dwellings that often yields a smaller calculated load by applying a single demand factor to the total connected load. Electricians commonly run both and use whichever legitimately produces the smaller service.
Load management as an alternative
NEC 625.42 and 750 permit energy management systems that shed load rather than forcing a service upgrade. A managed EV charger or a smart panel can frequently avoid a five-figure service upgrade, and is worth pricing before you commit.
Square footage alone does not size a service
A 3,000 square foot home with gas heat and no EV may calculate under 100 amps. The same home with a heat pump, electric range, and Level 2 charger can exceed 200 amps calculated. The appliances and fuel types matter far more than floor area.
Common questions
Do I need a 200 amp service?
It depends on your calculated load, not your house size. A 2,000 square foot home with gas heat and no EV often calculates under 100A. The same home with a heat pump, induction range and EV charger usually exceeds it.
Can I avoid a service upgrade for an EV charger?
Often yes. A load-managed charger, a lower charging amperage setting, or a smart panel that sheds other loads can keep you inside your existing service. The NEC explicitly allows these approaches.
How many amps does a house need?
A modern 2,000 square foot home with gas heat calculates at 80 to 120 amps using the NEC standard method. Add a heat pump, electric range, and Level 2 EV charger and the calculated load exceeds 150 amps — requiring a 200-amp service. A 100-amp service is insufficient for most new construction.
What size service for a 2000 sq ft house?
A 2,000 square foot home with standard appliances typically calculates at 100 to 150 amps. With electric heat, heat pump, or EV charging, it exceeds 150 amps and needs a 200-amp service. The calculated load — not the square footage — determines service size.
How many amps does an EV charger add?
A Level 2 EV charger at 40 amps (9.6 kW) adds 40 amps to the calculated load. A 48-amp charger adds 48 amps. Under NEC 625.42, a load-managed charger can be counted at its managed rate rather than full nameplate — often 20 to 32 amps.
What is the general lighting load per square foot?
NEC 220.12 requires 3 VA per square foot of dwelling unit floor area for general lighting and receptacles. A 2,000 square foot home has a 6,000 VA lighting load before demand factors. Table 220.45 reduces this: the first 3,000 VA at 100%, the remainder at 35%.
How do you calculate electrical load for a house?
Sum: general lighting (3 VA/sq ft with demand factors), fixed appliances at nameplate (with 75% demand if four or more), largest heating or cooling load, and other loads (EV, pool, workshop). Apply demand factors per NEC Table 220.45 and 220.53. The result is the minimum service size.
Is 100 amp service enough for a house?
For a home with gas heat, gas cooking, and no EV charger, 100 amps may suffice. Add an electric dryer, heat pump, induction range, or EV charger and the calculated load typically exceeds 100 amps. Most new construction and panel upgrades use 200-amp service.
How much does a 200 amp service upgrade cost?
A 200-amp panel upgrade runs $2,000 to $4,000 including the panel, breakers, labor, and permit. A full service upgrade with new meter base and service line runs $3,500 to $6,000. Utility fees for the meter upgrade add $500 to $1,500 in many areas.
What is the demand factor for a dryer?
A dryer is counted at 5,000 watts (or nameplate, whichever is greater) in the standard method. If four or more fixed appliances are present, NEC 220.53 allows a 75% demand factor on the combined appliance load. A single dryer is counted at 100%.
How many amps does a heat pump use?
A typical 3-ton heat pump draws 15 to 25 amps on a 240V circuit (3.6 to 6 kW). The backup heat strips add 15 to 30 amps additional. NEC 220.60 counts the larger of heating or cooling, not both simultaneously. A heat pump with 20 kW strips can add 83 amps to the calculated load.
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