EV Load Management
Splitvolt: EV Load Management Charger Size
The Splitvolt Splitter Switch is a circuit-share device. This is the charger it enables and the branch it needs, with the NEC basis declared by us and the manufacturer named only for how the device behaves.
How the Device Works
The device function: an automatic one-at-a-time interlock that time-shares a single existing 240V branch (a dryer outlet) between the appliance and the EV, so only one runs at a time. The Splitvolt Splitter Switch time-shares one existing 240V branch (typically a 30A dryer outlet) between the appliance and the EV through an automatic interlock; only one runs at a time. The EV output is capped at 24A (80% of the 30A branch) by its integrated breaker. This is not a service-level EMS - it is a branch-sharing device. An interlock guarantees the car and the appliance never draw at once, so the two are a noncoincident load under NEC 220.60, which permits counting only the largest of them. This tool does not ask which appliance is on the shared branch, so it does not know which is larger and does not compute that netting: the charger stays in the service calculation at its full NEC 220.57 value, which is the conservative end.
Adjustable range / setpoint: integrated 24/25A breaker; 24A continuous output on a 30A dryer branch.
Precondition: the existing shared branch (the 30A dryer circuit) must already be code-compliant for its own breaker (a 30A branch on #10 Cu) before a Splitvolt reuses it. A branch-sharing device does not fix an undersized existing circuit; confirm the host circuit with your electrician and the AHJ.
Charger & Branch by Rating
| existing shared-branch (dryer) breaker rating | Charger (80%) | Branch conductor | Branch breaker | Ground |
|---|---|---|---|---|
| 30A | 24A | #10 Cu | 30A | #10 Cu |
The branch is always 125% of the full EVSE hardware output (NEC 210.20(A) / 625.41). An external device never shrinks the branch. The one route the NEC gives for a smaller branch is the EVSE's own restricted-access adjusted setting under NEC 625.42(B), and it is a route a calculator cannot take for you: the conditions it attaches, under 750.30(C) and the manufacturer's instructions, are facts about installed equipment. The 4 this tool can name are not a full compliance checklist. Size from the full rating unless a qualified person has verified them, and 625.42(B) itself, on site.
Listing & Source
Listing: cETLus Intertek 5021938 / UL 60730-1
Device function transcribed from the manufacturer: Splitvolt documentation, accessed 2026-07-11. TYPE = circuit-share: an automatic one-at-a-time interlock on ONE existing branch. Output is 24A on a 30A dryer host ONLY (integrated 24/25A breaker). The 50A host / 40A output row does NOT ship (both sourcing passes) and is excluded - printing it would be a fire defect.
Frequently Asked Questions
How big an EV charger does the Splitvolt allow?
The Splitvolt time-shares one existing 240V branch (a dryer outlet) between the appliance and the EV, one at a time. On a 30A branch the EV output is 24A (80% of the branch breaker), on the existing #10 Cu / 30A circuit. An interlock guarantees the car and the appliance never draw at once, so the two are a noncoincident load under NEC 220.60, which permits counting only the largest of them. This tool does not ask which appliance is on the shared branch, so it does not know which is larger and does not compute that netting: the charger stays in the service calculation at its full NEC 220.57 value, which is the conservative end.
Does the Splitvolt let me use smaller wire?
No. The branch conductor and breaker are always sized to 125% of the full EVSE hardware output (NEC 210.20(A) / 625.41), never the circuit-share setpoint. The switch time-shares one existing branch through an automatic interlock; the branch it shares is sized as it always was. An interlock guarantees the car and the appliance never draw at once, so the two are a noncoincident load under NEC 220.60, which permits counting only the largest of them. This tool does not ask which appliance is on the shared branch, so it does not know which is larger and does not compute that netting: the charger stays in the service calculation at its full NEC 220.57 value, which is the conservative end. The one route the NEC gives for a smaller branch is the EVSE's own restricted-access adjusted setting under NEC 625.42(B), and it is a route a calculator cannot take for you: the conditions it attaches, under 750.30(C) and the manufacturer's instructions, are facts about installed equipment. The 4 this tool can name are not a full compliance checklist. Size from the full rating unless a qualified person has verified them, and 625.42(B) itself, on site.
What NEC sections cover the Splitvolt?
The load-management basis is our own derivation: NEC 220.70 permits an EMS-controlled maximum in the service or feeder load calculation, 625.42(A) relaxes the service and feeder for a listed EMS in accordance with 750.30, and 750.30 requires the EMS to keep load within conductor ampacity. The branch stays at 125% of the charger output (210.20(A) / 625.41). Splitvolt states the device function; the NEC basis is declared here, not attributed to the manufacturer.
Compute Your Biggest Charger
Enter your service and measured demand for the base NEC 220.87 answer, then compare it against what a circuit-share device unlocks.
Other Load-Management Devices
DCC (Thermolec / RC Devices / RVE)
shed (disconnect). EV charging-station pass-through breaker rating.
Emporia
throttle (current-modulating). EVSE hardware output (48A hardwired / 40A plug-in).
Wallbox
throttle (current-modulating). EVSE hardware output (48A / 40A models).
With vs Without Load Management
The same service, both ways: the biggest charger with and without a device.
Related Tools
EV Load Management Hub
The inverse 220.87 solve and all three device types.
Load Calculator (NEC 220)
The forward direction: 220.82 sizing and the 220.87 existing-load check.
EV Charger Calculator
Wire, breaker, and panel capacity for a Level 2 charger per NEC Article 625.
Wire Size Calculator
The correct conductor per NEC 310.16 with the 110.14(C) terminal cap.