Free · No sign-up · Works offline
An interactive wiring lab that behaves like the real thing. Place a breaker, run the cable, close the switch — and watch current actually flow, trip and fault.
Rated capacity
The simulator is only half of it. Around the canvas sit the modes and references that turn a wiring drawing into something you can learn from, practise on and hand over.
Twenty ready-made templates — protected lamp, two-way staircase, parallel lamps, dimmable lighting, doorbell, RCBO socket, RCD earth-fault demo, Pro SPD consumer unit — each lands on the canvas with an in-app checklist that ticks off as you wire it correctly.
Inject an open circuit, reversed polarity, an earth fault or an arc into any component or wire, then watch the right protective device respond live on the canvas — trip, blow or sit there blind, exactly as the physics says.
Every diagnosis exercise is deterministic from its seed. Copy it, paste it, get the identical circuit — so a lecturer can hand one code to the room and every learner faces the same fault.
Pro mode gates your circuit against the chosen standard before energising, runs Zs / disconnection-time checks, and exports a mini Electrical Installation Certificate style report for print or PDF.
Free calculators on the site: voltage drop and cable sizing against BS 7671 and IEC 60364 limits — each with a live scene, real presets and a shareable result URL. No sign-up, no tracking.
A spotlight Student tour builds your first circuit with you, step by step; the Pro tour walks the standards, diagnostics and fault tooling. Both advance by watching what you actually do.
Full keyboard control, reduced-motion support, a colour-blind canvas preset and a proper dark theme across the app and the site — the interface adapts to how you work, not the other way round.
Your settings travel as a profile backup file; circuits export as schema-versioned JSON, SVG or 2× PNG, or compress into a single share URL. Everything stays on your device — there is no account and no backend.
Every component is modelled — ports, poles, ratings and behaviour. Close a switch and the engine re-solves the Live, Neutral and Earth paths, then shows you what that means.
MCBs, RCDs, RCBOs, AFDDs, SPDs and MCCBs. Sockets for BS 1363, Schuko, US, AS/NZS and BS 546. Contactors, relays, timers, thermostats, transformers, 3-phase boards and motors.
The engine walks the real Live / Neutral / Earth topology. Energised wires animate current direction, bulbs glow to their wattage, fans spin and motors pulse.
Open neutral, missing earth, short to live, reverse polarity, overload. Protective devices trip because the circuit says they should — not because a script fired.
Two clicks and the router lays a tidy orthogonal path around obstacles — L-route in under a millisecond, A* for dense boards. Or draw the run yourself, checkpoint by checkpoint.
Regulatory gating before the simulation starts, Zs checks, and heat / voltage-drop diagnostics banded along the cable route. Teacher override is recorded as an audit event.
Schema-versioned JSON, animated SVG, 2× PNG, a printable title block, or a share URL that carries the whole circuit in the fragment. No backend, ever.
Free-build is where most simulators stop. These are the modes that tell you whether you got it right.
Hand-authored builds judged by an ordered rule checklist — protected lamp, momentary doorbell, RCBO-fed socket. Rules are checked on topology, not coordinates, so any electrically equivalent wiring passes.
The generator breaks a working circuit on purpose and hands it to you. Find the fault, prove it, repair it. Trip messages that would name the fault are withheld so the answer stays hidden.
Opt-in punishment. Compound faults, misleading symptoms and a timer. Electrically honest — never unfair — but it will not hold your hand.
No account, no download, no setup. Open it and start wiring.
Loads straight into the browser and keeps working offline after the first visit. Install it as an app if you want it on the home screen.
electrasim.com/appPick supply, protection, switching and loads from the palette. Everything snaps to the grid, and Pro mode recommends parts that match your standard and plug system.
PaletteClick a port, click the destination, and the router finds a tidy path around whatever is in the way. Port types are validated as you go.
Auto-routerRun the simulation, flip switches, then inject a fault and watch the protective device do its job. Undo is bounded to the last 100 states.
Live solverAnyone who needs to understand a circuit before touching one.
Practise domestic wiring with no shock risk and no consumables. Run the same exercise until the sequence is muscle memory.
Demonstrate live on a projector, then hand out one seed so every learner gets the identical fault to diagnose.
Sketch a board before you cut anything, prove a switching arrangement, or show a customer why the RCD keeps tripping.
Understand what is behind the faceplate. Relays, contactors, timers and PIR sensors, all safe to get wrong.
Regulations, circuit theory and step-by-step installs — the same material the simulator is built on.
A complete UK guide to electrical cable sizes — current ratings, maximum lengths, correct applications for every circuit type, and how to choose the right cable size for sockets, lighting, cookers and EV chargers.
Read article →Beginner GuideLearn how momentary push buttons work, the difference between normally open and normally closed contacts, and how they control doorbells and machinery.
Read article →Electrical SafetyFlickering lights can mean a loose bulb, an LED and dimmer mismatch, or a wiring fault. Learn safe checks, warning signs, and when to call an electrician.
Read article →Wiring GuideReverse polarity, missing earths, overloaded rings — these five wiring mistakes are found in thousands of UK homes. Learn what they are, why they're dangerous, how to spot them, and how to test your own circuits safely.
Read article →Wiring GuideRing circuits and radial circuits are the two ways to wire socket outlets in UK homes. This guide explains how each works, when to use each, cable sizes, spur rules, and how to simulate both topologies in a free browser-based circuit simulator.
Read article →Beginner GuideWhat do the brown, blue and green-yellow wires actually do? This complete guide explains the roles of live, neutral and earth in UK wiring, what happens when they're mixed up, and how to safely explore all three conductors in a free circuit simulator.
Read article →Wiring GuideTwo-way switching lets you control one light from two locations — the classic staircase circuit. This guide explains exactly how two-way switch wiring works, the role of COM, L1, and L2 terminals, strapping wires, and how to simulate the full circuit in a free electrical circuit simulator.
Read article →Beginner GuideThe distribution board is the heart of every electrical installation. This guide explains what's inside a consumer unit, how it distributes power to every circuit in a building, and how to simulate a multi-circuit distribution board using a free electrical circuit simulator.
Read article →Beginner GuideA contactor is an electrically controlled switch built for high-power loads. This guide explains how contactors work, where they're used, how they differ from relays and MCBs, and how to simulate a contactor circuit in a free electrical circuit simulator.
Read article →Beginner GuideAn RCD can disconnect a dangerous earth fault fast enough to save your life. This guide explains exactly how Residual Current Devices work, why they're mandatory in modern wiring, and how to test RCD protection safely using a free electrical circuit simulator.
Read article →How-to GuideNew to ElectraSim? This step-by-step guide shows you how to place components, draw wires, run a simulation, and read the fault log — all in your browser, for free.
Read article →Beginner GuideLearn how household electrical wiring works — from the main circuit breaker panel to your light switch. Understand live, neutral and earth wires, how MCBs protect your home, and what causes common faults.
Read article →Free, instant, and everything stays on your device. No account, no download, no risk.
Launch ElectraSimNow shipping
The learning release is live: Challenge Mode, the Diagnosis Lab and Ohmageddon join Guided Circuits, a live Fault Lab and the Electrical Toolbox — free, offline, no sign-up.
