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Service size, as a conversation, not a shopping list

“You need 200 A” is sometimes a diagnosis and sometimes an upsell. This tool runs a simplified optional calculation so you can tell which. It is not the load calculation an electrician stamps, and it is not a reason to open a panel yourself.

NEC 220.82 shape, not a stamp 100% of the first 10 kVA of general load, 40% of the remainder, HVAC at 100%, EVSE at 125% as a continuous load. Your jurisdiction adopts an edition of the NEC. This page does not declare your house illegal.

Enter floor area, nameplate VA for range, dryer, water heater and HVAC, optional EV amps, and the existing service size if you know it. The output is an ampere figure at 240 V and whether that figure overshoots the existing service on these inputs. Live work is not DIY. HyreElectrical does not perform electrical work.

Nameplates in, amps out

Not a stamp. Nothing is emailed. Do not open the panel to read this.

3 VA per sq ft general lighting, NEC shape.

0 if the heater is gas.

The larger of heating and cooling, as on the nameplate.

0 if none. Treated as continuous (×1.25).

0 if unknown. 60, 100, 150, 200 are the common residential sizes.

— Calculated demand
— Volt-amperes
— Against existing service
— The conversation

What this assumed —

A simplified optional calculation, not a stamped load calc. Live work is not DIY. HyreElectrical does not perform electrical work.

Questions this calculator answers

What size electrical service do I need?
A licensed electrician calculates it from the adopted NEC edition and the actual nameplates in the house. This tool is a neighbourhood check in the shape of the optional calculation in 220.82, so a “you need 200 A” pitch has something to be compared against.
Is 100 A enough for a heat pump and an EV charger?
Often not, once both are treated as large continuous loads. Run the numbers with your nameplates. Spare capacity on this page is illustrative.
Can I DIY a service upgrade?
No. Service work is licensed work. This page will not walk you through it.

Sources and methodology

Figures dated 23 August 2026. Last reviewed .

  • NFPA 70, National Electrical Code, Article 220 (NFPA, retrieved 2026-08-23. Cited as the model code. The optional-calculation shape used here is a simplification, not a reproduction of the article. Confirm the edition your jurisdiction adopted.)

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