Residential Electrification Load Scenario Calculator

The Residential Electrification Load Scenario Calculator estimates the peak demand created when a home adds or replaces electric equipment such as a heat pump, heat-pump water heater, induction range, electric dryer, or EV charger. Its primary planning result is Scenario peak: the existing residential peak plus the proposed coincident peak contribution of each equipment change.

That result is used early in a service or feeder review to compare an electrification package against the project’s available planning capacity. It helps identify whether the proposed package appears to fit within the entered capacity or whether load management, equipment changes, or a more detailed electrical design review may be needed.

The calculator does not use a hidden equipment database. Each load value is entered directly, allowing the scenario to reflect the actual equipment assumptions, operating strategy, and likely simultaneous operation being evaluated.

Planning Capacity and Scenario Peak

Residential electrification can increase connected load substantially without producing an equal increase in probable peak demand. A 9.6 kW EV charger, for example, may be electrically connected at its full rating but may not operate at the same time as every other major household load. Conversely, an unmanaged EV charging period can coincide with heating, water heating, cooking, and existing household demand.

The calculation begins with Existing base peak (kW). This is the estimated peak already present in the dwelling before the proposed package rows are added. It is not the home’s total connected load; it is the existing peak assumed for the planning scenario.

Entered panel or service planning capacity (kW) is the capacity used as the comparison threshold. The calculator does not select, approve, or verify that capacity. Service equipment ratings, feeder ampacity, conductor sizing, terminal ratings, voltage system, meter equipment, utility requirements, and the approved load calculation remain separate design decisions.

Each proposed equipment change is entered under Existing and proposed equipment rows using:

Field	Electrical use
Equipment label	Identifies the appliance, HVAC equipment, charging equipment, or other load change
Existing electric connected load (kW)	Connected electric load being removed or replaced
Proposed electric connected load (kW)	Connected electric load after the proposed change
Proposed coincident peak contribution (kW)	Portion of the proposed load expected to contribute to the scenario peak

Use zero for Existing electric connected load (kW) when replacing fuel-fired equipment or another non-electric baseline. For example, replacing a gas water heater with an electric heat-pump water heater normally uses 0 kW as the existing electric connected load, assuming the gas appliance did not have a comparable existing electric heating load.

Connected Load and Coincident Demand

Proposed connected load total shows the full nameplate-style electrical load entered for all proposed equipment rows. It is useful for seeing the size of the electrification package, but it is not automatically the expected simultaneous demand.

Scenario peak uses Proposed coincident peak contribution (kW) rather than each row’s full proposed connected load. This allows the planning model to recognize an operating assumption such as managed EV charging, staged water heating, or equipment that is unlikely to operate at full output during the same peak period.

The calculator reports the following values:

Result	Formula behavior
Existing connected load total	Sum of all Existing electric connected load (kW) entries
Proposed connected load total	Sum of all Proposed electric connected load (kW) entries
Incremental connected load	Proposed connected load total minus existing connected load total
Scenario peak	Existing base peak plus the sum of all Proposed coincident peak contribution (kW) entries
Capacity margin	Entered panel or service planning capacity minus Scenario peak
Required control or reduction screen	The amount by which Scenario peak exceeds entered planning capacity; 0 kW when Scenario peak does not exceed capacity

The calculation can be written as:

\(\displaystyle \text{Existing connected load total} = \sum \text{Existing electric connected load}\)

\(\displaystyle \text{Proposed connected load total} = \sum \text{Proposed electric connected load}\)

\(\displaystyle \text{Incremental connected load} = \text{Proposed connected load total} - \text{Existing connected load total}\)

\(\displaystyle \text{Scenario peak} = \text{Existing base peak} + \sum \text{Proposed coincident peak contribution}\)

\(\displaystyle \text{Capacity margin} = \text{Entered panel or service planning capacity} - \text{Scenario peak}\)

\(\displaystyle \text{Required control or reduction screen} = \max(0,\ \text{Scenario peak} - \text{Entered panel or service planning capacity}\)

A positive Capacity margin indicates that the entered scenario remains below the entered planning capacity. A negative margin means the scenario exceeds that planning capacity. Required control or reduction screen expresses that excess as a positive kW value.

Calculation Example

Consider an existing residence with an Existing base peak (kW) of 6 kW and an Entered panel or service planning capacity (kW) of 19.2 kW.

The proposed electrification package includes a heat pump, EV charger, and water heater:

Equipment label	Existing electric connected load (kW)	Proposed electric connected load (kW)	Proposed coincident peak contribution (kW)
Heat pump	0	4.8	3.6
EV charger	0	9.6	7.2
Water heater	0	4.5	2.0

The connected-load totals are:

\(\displaystyle 0 + 0 + 0 = 0 \text{ kW Existing connected load total}\)

\(\displaystyle 4.8 + 9.6 + 4.5 = 18.9 \text{ kW Proposed connected load total}\)

\(\displaystyle 18.9 - 0 = 18.9 \text{ kW Incremental connected load}\)

The coincident demand added to the existing base peak is:

\(\displaystyle 3.6 + 7.2 + 2.0 = 12.8 \text{ kW}\)

\(\displaystyle 6.0 + 12.8 = 18.8 \text{ kW Scenario peak}\)

The available planning margin is:

\(\displaystyle 19.2 - 18.8 = 0.4 \text{ kW Capacity margin}\)

Because the calculated scenario peak is below the entered planning capacity:

\(\displaystyle \max(0,\ 18.8 - 19.2) = 0 \text{ kW Required control or reduction screen}\)

The result is a Scenario peak of 18.8 kW, a Capacity margin of 0.4 kW, and a Required control or reduction screen of 0 kW. The narrow margin indicates that changes to the assumed EV charging overlap, heat-pump operation, water-heater operation, or existing base peak could change the planning result.

Field Verification

The calculator compares entered kW assumptions; it does not perform a code load calculation or establish conductor ampacity. A final residential service, feeder, or branch-circuit decision requires the actual electrical design inputs, including voltage, phase, equipment ratings, continuous-load treatment where applicable, overcurrent protective devices, conductor material, AWG or kcmil conductor size, insulation temperature rating, terminal rating, and installation conditions.

A calculated scenario that appears to fit within planning capacity can still require additional review for:

• Service and feeder conductor ampacity
• Main breaker, panelboard, meter, and service-equipment ratings
• Individual branch-circuit ratings for EV charging equipment, HVAC equipment, water heaters, dryers, and cooking equipment
• Voltage drop on long feeders or branch circuits
• Raceway fill, conductor count, and current-carrying conductor adjustment factors
• Ambient-temperature correction factors
• Load-control equipment operating sequence and failure mode
• Utility requirements and AHJ approval

The Proposed coincident peak contribution (kW) must be supported by a real operating assumption. If the scenario depends on managed EV charging, water-heater shedding, HVAC staging, or other control, the field design must verify that the control strategy is installed, reliable, and consistent with the intended electrical load review.