Detached Studio or Home Office Wiring: What You Need to Know

October 16, 2026 · Family-owned electricians in North Idaho

Public domain, via Wikimedia Commons

If you're converting a shed into a studio or building a standalone office, the electrical work is usually bigger than people expect. It's rarely a single extension cord run. Most detached buildings need their own subpanel, dedicated circuits for lighting and outlets, and enough capacity to run a heater through a North Idaho winter. Budget for a permitted subpanel installation, trenching for underground feed, and likely a load calculation to size it right. Costs vary a lot by distance from the main panel and how much heat you plan to run, but a basic detached office setup often lands in the range of a few thousand dollars once trenching and permits are included.

This post is for homeowners, cabin owners, and small business owners in Bonner and Kootenai counties planning a detached studio, office, or workshop. It's not a full how-to for pulling your own permit and doing the work solo. It's here so you know what's actually involved before you call someone or pick up a shovel.

What you need

• A subpanel sized for the building's actual load, not just what fits in the box. Common sizes are 60, 100, or 125 amp depending on heating and equipment plans.
• Feeder cable or conduit rated for underground use (UF cable or conduit with THWN conductors), sized for the amperage and the distance from the main panel. Longer runs need larger wire to avoid voltage drop.
• A disconnect at the detached structure if local code requires it, which is common for any outbuilding with its own panel.
• Dedicated circuits: at minimum one for general lighting and outlets, often two or more if you're running a kiln, welder, mini-split heat pump, or multiple workstations.
• GFCI protection on all outlets, since detached buildings are treated like garages and outdoor spaces under current code.
• A heating plan with real numbers. Electric baseboard, a wall heater, or a ductless mini-split all draw different amperage, and that load has to be in the calculation from the start.
• A permit and inspection. Detached structures with their own power source almost always require one in Idaho.

Step by step

1. Calculate the load first. Add up lighting, outlets, and any heat or equipment you plan to run, including future additions like a mini-split or power tools. This number determines subpanel size, wire gauge, and trench depth requirements. Guessing low here is the most common and most expensive mistake.
2. Plan the route and trench depth. Direct-burial cable in Idaho typically needs to be at least 24 inches deep, sometimes 18 inches if it's in conduit with GFCI protection, but local frost depth and soil conditions matter. Mark utilities before digging. A shallow trench that gets nicked by a shovel or a post hole digger later is a real and recurring problem.
3. Install the subpanel and feeder. The feeder size depends on both the load and the distance. A 100 amp subpanel 150 feet from the house needs noticeably larger wire than the same panel 30 feet away, because voltage drop increases with distance. This is where a lot of DIY jobs undersize the wire and end up with dimming lights or underperforming heaters.
4. Rough in circuits and finish with an inspection. Separate circuits for lighting, general outlets, and any heavy equipment. Once everything is roughed in, a licensed inspector checks it before the walls close up. Skipping this step is common on shed conversions and it's the one that causes problems at resale or insurance claims later.

Where this goes wrong

The most common failure is sizing the subpanel for today's plan instead of a realistic future one. Someone wires a 60 amp subpanel for lights and a space heater, then a year later wants to add a mini-split or a kiln, and there's no room left. Upsizing after the fact means redoing the feeder and sometimes the trench, which costs far more than sizing it right the first time.

Voltage drop from an undersized feeder over a long run is another frequent issue. Symptoms show up as lights that dim when a heater kicks on, or a mini-split that struggles to hit temperature. It's not always obvious right away, and it's expensive to fix after the fact because it usually means pulling new conductors through conduit or re-trenching.

Heating load gets underestimated more than anything else out here. A detached studio with single-pane windows or minimal insulation can need a surprising amount of heat to stay usable through a North Idaho winter, and if the panel and circuit weren't sized with that in mind, the heater either trips breakers constantly or just can't keep up. This is especially common with electric baseboard heat added as an afterthought to a shed conversion that was originally wired just for lights and a few outlets.

Burial depth is another one. Trenches that end up shallower than code, whether from rocky soil, impatience, or just not knowing the requirement, create a real hazard for anyone digging a fence post or garden bed later. It's not visible until someone hits it, and by then it's a repair and sometimes a safety incident.

Finally, skipping the permit is tempting on a small outbuilding, but it creates problems later. Unpermitted electrical work can complicate home insurance claims, and it can come up during a home sale inspection, sometimes requiring the work to be opened up and reinspected.

When to stop and call someone

Running a single extension cord for a light in a small shed is a low-risk project. Installing a subpanel, trenching a feeder, or wiring circuits for heat is not. Here's where it makes sense to bring in a licensed electrician instead of handling it yourself:

• Any time you're adding a subpanel. This involves main panel work, breaker sizing, and grounding/bonding rules that are easy to get wrong and dangerous when they're wrong.
• Any underground feeder run. Depth requirements, conduit type, and conductor sizing for distance all affect safety and performance, and mistakes are buried and hard to diagnose later.
• Sizing for electric heat or a mini-split. These loads are large relative to typical lighting circuits, and undersizing creates both a performance problem and, in some cases, a fire risk from an overloaded circuit.
• Anything that needs a permit, which in most of Bonner and Kootenai counties includes any new subpanel or detached structure with its own electrical service.

If you're planning a detached studio or office and want the load calculation and panel sizing done right the first time, Sageland Electric handles this kind of work regularly across North Idaho and can walk through the heating and equipment plans with you before anything gets trenched in.