This free split-screen designer pairs a 3D model of a two-story dwelling with a live one-line diagram of its electrical system, so you can see how power flows from the service entrance through the main panel to every branch circuit. Click any device — receptacle, breaker, smoke detector, or EV charger — in either view to cross-highlight it across the model and the one-line. It's a visual learning tool for homeowners, electricians, designers, and students learning residential wiring per NEC 2020.
The designer covers the whole dwelling electrical system, paired live with the one-line:
• Service entrance and meter — the utility drop or lateral, meter socket, and service-entrance conductors feeding the home. • Main panel (load center) — the main breaker and bus that distributes power to all branch circuits. • AFCI and GFCI breakers — protection devices that interrupt arc faults and ground faults at the panel. • Branch circuits — the individual lighting, receptacle, and appliance circuits routed to each room. • Lighting and devices — fixtures, switches, and receptacles placed throughout the dwelling. • Smoke and CO alarms — interconnected life-safety devices. • EV charger — a dedicated 240V circuit for electric-vehicle charging per NEC 625. • Low-voltage — doorbell, thermostat, and data/comms wiring.
Utility power reaches the home through the service entrance and meter, then lands on the main panel (load center). The main breaker protects the service, and a bus distributes the two 120V legs (240V across them) to branch-circuit breakers. Each breaker feeds one circuit sized to its load — 15A or 20A for general lighting and receptacles, larger circuits for the range, dryer, HVAC, and EV charger. AFCI breakers protect most living-area circuits against arcing faults, while GFCI protection guards wet-location and outdoor receptacles. Smoke and CO alarms are interconnected so that any one triggering sounds them all, and low-voltage systems run alongside the line-voltage wiring.
1. Drag to orbit the house, scroll to zoom, and pan to move around the 3D model. 2. Click any device, fixture, or breaker to highlight it and cross-reference it on the live one-line diagram. 3. Trace each circuit from the service entrance → meter → main panel → breaker → branch circuit to the device it serves, and note which circuits carry AFCI or GFCI protection.
Under NEC 2020, AFCI protection is required for most 120V, 15A and 20A branch circuits serving living areas — bedrooms, living rooms, kitchens, hallways, and similar spaces. GFCI protection is required for receptacles in wet or damp locations: bathrooms, kitchens (countertop receptacles), garages, outdoors, crawl spaces, unfinished basements, laundry areas, and near sinks. Many circuits now use dual-function AFCI/GFCI breakers to meet both.
The service entrance is the point where utility power enters the building — the service drop (overhead) or lateral (underground), the meter, and the service-entrance conductors that run to the main panel. It includes the main service disconnect, which is the single switch that cuts all power to the dwelling.
Panel (service) size is found with an NEC Article 220 load calculation: sum the general lighting and receptacle load (based on square footage), small-appliance and laundry circuits, fixed appliances, and the largest of heating or cooling, then apply NEC demand factors and divide by 240V. Most modern single-family homes land on a 200A service, though smaller homes may use 100A or 150A and large all-electric homes more.
A branch circuit is the wiring between the final overcurrent device (the breaker in the panel) and the outlets or devices it serves. The breaker rating sets the circuit — a 20A breaker protects a 20A circuit wired with 12 AWG copper, for example — and one circuit may serve several receptacles or a single dedicated load like the range or EV charger.
A Level 2 home EV charger is a dedicated 240V branch circuit installed per NEC Article 625, typically 40A–60A wired with appropriately sized conductors, often on a GFCI-protected breaker. The circuit is sized to the charger output (commonly continuous load at 125%), and the panel must have spare capacity confirmed by a load calculation.