What Size Electrical Panel Do I Need?
Most homes need either a 100A or 200A panel, and the real answer depends far more on what you plug in than on how big your house is. A 1,200 sq ft home with an electric range, electric water heater, and an EV charger can need more capacity than a 3,000 sq ft home heated and cooked with gas. This guide covers the rule-of-thumb numbers, what each panel size can actually handle, the breaker-slot question people often confuse with amperage, and the one way to get a real answer instead of a guess.
⚡ Key Takeaways
- Square footage is a rough starting point only — what you actually plug in matters more
- 100A ≈ 24,000W total, 200A ≈ 48,000W total, but the NEC 80% rule caps continuous load at 80A / 160A respectively
- Breaker slot count (physical space) and amperage rating (current limit) are two separate specs — a panel can run out of either one independently
- 100A panels commonly offer 20-42 slots; 200A panels commonly offer 30-42+, varying by manufacturer
- The only reliable sizing method is an actual NEC Article 220 load calculation, not a square-footage guess
The Quick-Answer Table by Home Size
Electricians and panel manufacturers commonly cite square-footage ranges as a rough starting point for what size electrical panel a house needs. Treat this as a first guess, not a final answer — the section after it explains why.
| Panel size | Typical home profile | Rough sq ft range |
|---|---|---|
| 100A | Mostly gas appliances, minimal electric heating or cooling load | Under ~2,000 sq ft |
| 150A | Mixed gas/electric, moderate appliance load | ~1,500-2,500 sq ft |
| 200A | Standard for new construction; needed for EV charging, heat pumps, electric appliances | ~2,000-3,500 sq ft, or any size with heavy electric loads |
| 400A | Large or all-electric homes, multiple heavy loads (pool, multiple EV chargers, large HVAC) | 3,000+ sq ft, or smaller homes that are fully electrified |
⚠️ Square footage is a weak predictor on its own. Electrician forum consensus and manufacturer guidance agree that what you actually run — gas vs. electric heat, electric vs. gas range, how many large 240V appliances — changes the real number far more than home size does. Use the table above to get oriented, then use the load calculator below for your actual answer.
How Many Amps Does a House Actually Need?
"How many amps does a house need" does not have one number, because it is really two separate questions: how much your panel can supply (its rating — 100A, 200A, etc.) and how much your home actually draws at once (your demand load, calculated under NEC Article 220). A small, all-gas home might have a real demand load under 40-50A even sitting on a 100A panel — plenty of headroom. A similarly sized all-electric home with a heat pump, electric range, electric water heater, and an EV charger can push demand load past 150A, which is why that home needs 200A service even though the house itself is not larger.
This is also why two neighbors in identical houses can get different answers from an electrician: the panel size question is really an appliance-mix question wearing a house-size costume.
How Much Power a 100A vs 200A Panel Can Handle
| 100A panel | 200A panel | |
|---|---|---|
| Total theoretical capacity | ~24,000W (100A × 240V) | ~48,000W (200A × 240V) |
| NEC 80% continuous-load cap | ~80A continuous (~19,200W) | ~160A continuous (~38,400W) |
The NEC's 80% continuous-load rule is why electricians do not simply multiply amps by volts and call it your usable capacity. Code requires that continuously-operating loads (3 hours or more, like HVAC or EV charging) not exceed 80% of the breaker or panel rating — the other 20% is safety headroom against heat buildup. Short-duration loads can briefly use more, but your working planning number for a 100A panel is closer to 80A of continuous draw, not the full 100A.
If you are specifically wondering whether your panel can take on one more thing — an EV charger, a heat pump, an induction range — this math is exactly what our free load calculator runs for your specific home instead of a rule of thumb.
How Many Breakers Can a Panel Have? (A Different Question)
People often assume "200A panel" tells you how many circuits it supports, but breaker slot count and amperage rating are two independent specifications set by the panel's physical design, not its amp rating:
| Panel rating | Typical full-size slot range |
|---|---|
| 100A | Roughly 20-24 slots on common models, with some compact or expanded models ranging 12-42 |
| 200A | Roughly 40-42 slots on common models, with some compact or expanded models ranging 30-60+ |
Two practical consequences follow from this:
- A panel can run out of slots before it runs out of amperage, or the reverse. A 200A panel that is physically full of breakers can still be well under its 160A continuous-load cap — the fix there is a subpanel, not a bigger main panel. See our subpanel installation guide if that's your situation.
- Tandem (twin/half-height) breakers can add circuits without adding amperage, where the panel and breaker manufacturer both support them — but they do not increase your panel's total current limit, only its circuit count.
Your panel's exact slot count and amp rating are both printed on the label inside the door — see our how to read your electrical panel guide for exactly what to look for.
The Real Way to Size a Panel: Load Calculation
Every method above is a shortcut. The method a licensed electrician actually uses — and the one required for a permitted panel upgrade — is a load calculation under NEC Article 220. In broad strokes, it works by:
- General lighting and receptacle load: 3 volt-amps per square foot of living space (NEC 220.12)
- Small-appliance and laundry circuits: a fixed 1,500W allowance for each required kitchen/laundry circuit (NEC 220.52)
- Fixed appliance nameplate loads: actual rated watts for your range, water heater, dryer, HVAC, EV charger, and similar
- Demand factors: the code allows counting only a portion of some loads at full value, since not everything runs at once (NEC 220.42, 220.45)
- Convert to amps and compare to your panel: total volt-amps ÷ 240V gives your real demand load in amps, which you then compare against your panel's rating
Run the Real Numbers for Your Home
Our free calculator follows this same NEC Article 220 method — enter your home size and appliances, get your actual answer in under a minute.
⚡ Run Free CalculatorIf the calculator shows you are already close to your panel's limit, or you are planning a project that will push you over it, see our panel upgrade cost guide for what the next step actually costs, and our 100A vs 200A comparison for a deeper look at which size fits your situation.
Frequently Asked Questions
Q: What size electrical panel do I need for a house?
A: Most homes under roughly 2,000 sq ft with mostly gas appliances do fine on a 100A panel. Homes over 2,000 sq ft, or any size with significant electric loads — electric heat, an electric range, an EV charger, a heat pump — typically need 200A, which is also the standard choice for new construction. These are starting points, not a substitute for an actual load calculation, since appliance mix matters more than square footage alone.
Q: How many amps does a house need?
A: There is no single number — it depends on what is actually drawing power, not just the home's size. A small home with all-gas appliances might run comfortably under 60A of actual demand even on a 100A panel. A similarly sized all-electric home with a heat pump, electric range, and EV charger can approach or exceed 150A of demand, which is why that second home needs 200A service even though the house itself isn't larger.
Q: Can I add an EV charger to a 100-amp panel?
A: Often yes, if your existing load leaves enough headroom under the NEC 80% continuous-load rule — roughly 80A of usable capacity on a 100A panel. A 40A EV charger circuit (common for Level 2 home charging) needs real headroom to fit safely alongside your existing appliances. The only reliable way to know is to run the numbers for your specific home, which is exactly what a load calculator is for.
Q: Is a 150-amp panel a real option, or just 100A and 200A?
A: 150A panels exist and are sometimes used as a middle-ground upgrade, but they are less common than 100A and 200A and not every manufacturer offers every breaker type for them. Most electricians default to recommending 200A for any upgrade, since the incremental cost over 150A is usually small and it leaves more future headroom for electrification.
Q: Does a bigger panel mean more breaker slots?
A: Not directly — amperage rating and breaker slot count are two separate specifications. A 100A panel is commonly available with anywhere from about 20 to 42 slots depending on the model, and a 200A panel commonly ranges from about 30 to 42 slots, with some models offering more. A panel can run out of physical slots for new circuits long before it runs out of amperage, or vice versa — check your specific panel's slot count and amp rating separately.
Sources
Panel capacity and NEC continuous-load figures were checked against NEC code-reference sourcing and manufacturer documentation. Typical breaker slot-count ranges and square-footage sizing guidance were cross-checked against multiple current home-improvement cost guides, including The Home Depot, and against electrician discussion on Mike Holt's electrical forum, which was the basis for the square-footage caveat above — appliance mix is the more reliable predictor across that sourcing, not home size alone. Slot counts and amp ratings vary by manufacturer and model; always confirm against your specific panel's label.