EMS Load CalculatorService capacity planning with energy management NEC 2023
What This Tool Checks:
Evaluates whether an existing electrical service can support additional loads (EV chargers, heat pumps, water heaters, or HVAC) using an Energy Management System (EMS) without a service upgrade, or determines the required service size for new dwellings with EMS.
NEC 2023 §§220.70, 220.82, 625.42(A), and 750.30. Subject to equipment listing and AHJ approval.
1Existing/New Electrical Service
2New loadsMajor loads
3EMS configuration
4Evaluation
1. Existing Electrical ServiceNew Electrical Service
Check whether the existing service can take the new loads with EMS.Find the service size needed with EMS and without EMS.
Enter the calculated demand or 125% of the qualifying peak demand from 12-month data or a 30-day recording (NEC 2023 §220.87).
Enter the NEC 2023 Article 220 calculated demand for the new dwelling, without the major loads entered in Step 2. (§220.87 measured demand applies only to existing services.)
NEC 2023 §220.82 — Single Dwelling Optional Method. Existing or new dwelling; enter EMS-managed loads in Step 2. General loads (3 VA/sf, small-appliance and laundry circuits, appliances and motors at nameplate): first 10 kVA at 100%, remainder at 40%. Heating/cooling: larger of the §220.82(C) options. EV charger: 100%.
Unit Details
Use the dwelling floor area applicable under NEC 220.5(C).
Existing Fixed AppliancesDwelling Fixed Appliances — Nameplate VA
Dwelling EV charger (nameplate). Add EMS-managed chargers in Step 2. Counted at 100% (no demand factor), as in the Single Dwelling Unit calculator.
Existing Heating and CoolingHeating and Cooling
The larger of heating or cooling is used (NEC §220.82(C)).
Condensing unit or heat pump. 0 if none.
AHU/FCU fan motor only (excludes supplemental heat).
2. Proposed New Electrical LoadsMajor Loads for EMS Management
Add multiple EV chargers, water heaters, HVAC equipment or other new loads. Input actual operating nameplate current, not just the breaker size.
Load
Type
Qty
Voltage
Operating A (each)
EMS controlled?
Load Calculation Without EMS
Review the existing demand plus all new loads before selecting an EMS configuration.Review the dwelling demand plus all major loads before selecting an EMS configuration.
Existing demandDwelling demand
—
New loadsMajor loads
—
Total demand without EMS
—
Existing service capacityRecommended service
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3. ZigTech EMS Configuration
A
19.2 kVA80% of 100 A service
Maximum: 80A (80% of the 100A service rating).
NEC 2023 §220.70: the EMS setpoint is treated as a continuous load in the load calculation, so the service must be rated at least 125% of the setpoint. The setpoint therefore may not exceed 80% of the service rating.
AHJ Approval: The proposed ZigTech EMS installation and load-management approach must comply with applicable NEC 2023 requirements and are subject to review and approval by the Authority Having Jurisdiction (AHJ).
