200 amp vs 100 amp panel
A 200 amp service has twice the rating of a 100 amp one. For all-electric additions like an EV charger and a heat pump, that extra room can change the result from over to fits.
The same home on both
Illustrative home, not yours: 1,800 sq ft, electric range (12,000 VA), electric dryer (5,000 VA), electric water heater (4,500 VA), 2,000 VA of other fixed appliances and a 4,000 VA central A/C.
EV charger (40 A) and 3-ton heat pump, on a 100 A service:
| General loads: lighting at 3 VA per sq ft, two 1,500 VA small-appliance circuits, 1,500 VA laundry, plus range, dryer, water heater and other fixed appliances, plus the charger (40 A x 240 V x 125% = 12,000 VA) | 45,400 VA |
| First 8,000 VA at 100%, the rest at 40% | 22,960 VA |
| Heat pump (3 tons at about 1,200 VA per ton) in place of central A/C | 3,600 VA |
| Total, divided by 240 V | 110.7 A |
| Against a 100 A service | 111% (over, above 100%) |
The same home and equipment on a 200 A service:
| General loads: lighting at 3 VA per sq ft, two 1,500 VA small-appliance circuits, 1,500 VA laundry, plus range, dryer, water heater and other fixed appliances, plus the charger (40 A x 240 V x 125% = 12,000 VA) | 45,400 VA |
| First 8,000 VA at 100%, the rest at 40% | 22,960 VA |
| Heat pump (3 tons at about 1,200 VA per ton) in place of central A/C | 3,600 VA |
| Total, divided by 240 V | 110.7 A |
| Against a 200 A service | 55% (fits, 80% or less) |
What to weigh
- Whether you plan to add more electric equipment later.
- Your current result with the equipment you want today.
- Quotes: an upgrade can involve the panel, the service and the utility, so get written quotes.
How Panel Check estimates it
Panel Check uses an NEC-style optional method for existing homes. It adds general loads, counts the first 8,000 VA in full and the remainder at 40%, adds the larger of cooling or heating, then divides by 240 V to get amps. An EV charger is treated as a continuous load, so its breaker size is multiplied by 125%. A result at or under 80% of the service rating reads as fits, up to 100% as tight, and above that as over. The heat pump figure is a rule of thumb; the nameplate on your equipment is the real number.
Frequently asked questions
Is 200 amps always enough?
Not always, but it has far more room. Run your numbers to see.
How do I find my current service size?
It is usually printed on the main breaker. A licensed electrician can confirm it.
Should I upgrade just in case?
That is a cost and planning decision. Use the estimate to see how close you are, and discuss it with an electrician.
Try it on your own numbers
This is a planning estimate, not an electrical design. A licensed electrician must confirm your actual panel, wiring and local code requirements before any work. Nothing here is a guarantee of safety or code compliance.