Service Upgrade for a 1,500 sq ft Dwelling Adding an EV Charger

Step 1 - 220.82(B) general loads

• General lighting: 1,500 sq ft x 3 VA = 4,500 VA
• Small appliance: 2 x 1,500 VA = 3,000 VA
• Laundry: 1,500 VA
• Other fastened-in-place/appliance loads: 12,000 + 5,500 + 4,500 + 1,200 + 900 + 1,500 = 25,600 VA
• Subtotal = 4,500 + 3,000 + 1,500 + 25,600 = 34,600 VA

Apply the 220.82(B) demand factor: 100% of the first 10 kVA plus 40% of the remainder.

• 10,000 + 0.40 x 24,600 = 10,000 + 9,840 = 19,840 VA

Step 2 - 220.82(C) heating/cooling

• Cooling: 5,600 VA
• Heat pump compressor at 100% plus 65% of supplementary heat: 5,600 + 0.65 x 8,000 = 10,800 VA

Use the larger: 10,800 VA.

Step 3 - Total

19,840 + 10,800 = 30,640 VA

30,640 / 240 V = 127.7 A

The next standard rating per 240.6 is 150 A, so the minimum is a 150 A service. The existing 100 A service is already inadequate for the existing dwelling load, independent of the EV charger, which is why the utility will not simply reconnect.

With the EVSE

The EV charger is added at 100% (it is a continuous load; 625.41 requires the branch circuit to be sized at 125% of the EVSE rating, and the load itself is not subject to the 220.82(B) 40% factor):

30,640 + 9,600 = 40,240 VA -> 40,240 / 240 = 167.7 A

Next standard size above 167.7 A is 175 A; practically the answer is a 200 A service, since 175 A residential equipment and metering are not commonly stocked and the panel needs spare spaces anyway.

Alternatives to a service change

1. Derate the EVSE. A 16 A (3,840 VA) setting gives (30,640 + 3,840) / 240 = 143.7 A, which fits a 150 A service. A 24 A setting (5,760 VA) gives 151.7 A and does not fit 150 A. Load calculations, not nameplate charger size, drive this - a smaller setting is a legitimate design choice.
2. NEC 220.87 existing-load calculation. Record the actual maximum demand over 30 days (utility interval data or a recording meter). If 125% of the measured demand plus the new load fits the existing service, the calculation may be used instead of 220.82. Flickering lights or an undersized panel do not disappear, though.
3. Energy management / load control per 625.42(B), which permits a listed EMS to control the EVSE so it cannot operate simultaneously with the largest other loads, with the service sized to the controlled load.

Any of these must be documented for the inspector; the service rating itself is not reduced by conductor sizing rules such as 310.12.

Licensing

• The work must be performed by or under an electrical contractor licensed through the Building Codes Division, using a licensed journeyman (or a properly supervised apprentice). A handyman, a general contractor, or a homeowner's helper cannot legally do it (ORS chapter 479; OAR chapter 918, division 282).
• An apprentice may not work alone on a service change; supervision and ratio requirements apply.

Permit and inspection

• An electrical permit is required before the work starts, obtained from the local jurisdiction, or from BCD where no local electrical program exists. The permit must be posted and the inspection requested.
• Because the service conductors are being replaced, the utility must be coordinated with for the disconnect and reconnect. The electrician does not cut the service drop, pull the meter, or re-energize the service - that is utility work, and energizing ahead of inspection is prohibited.
• The service equipment inspection includes the grounding electrode system (250.50, 250.66), main bonding jumper (250.28), separate grounded/equipment grounding terminals in the panel (408.41 / 200.85), working clearance (110.26), and the load calculation supporting the new rating. A final inspection must be approved before the utility reconnects.

Owner exemption

Oregon's owner exemption is narrow: it covers the owner of a single-family dwelling the owner occupies, and a permit and inspection are still required. It does not extend to a rental property, a relative's house, or work done for hire.