Subpanel Installation in Twin Falls, Idaho — Garages, Shops, Additions & Barns
A subpanel gives a garage, shop, addition or outbuilding its own breakers without overloading your main panel. We size it with a load calculation, pull the City of Twin Falls permit and take the job through inspection.
A second breaker panel, fed from your main panel
A subpanel is a smaller breaker panel connected to your main panel by a heavy feeder cable. It puts circuits close to where you use them — a detached shop, a finished basement, a barn — and leaves your main panel available for the rest of the house.
Detached garage or shop
Lighting, outlets and 240V tools in a separate building need a feeder run from the house and a properly grounded subpanel at the building.
Additions and finished basements
New rooms add circuits your main panel may not have room for. A subpanel avoids crowding or double-tapping breakers.
Barns and farm buildings
Shop, stall and equipment circuits are easier to manage with a subpanel at the building. See our agricultural electrical work.
Hot tubs, welders and compressors
High-draw 240V equipment often needs its own breaker and disconnect. See hot tub wiring.
EV chargers
A subpanel in the garage can serve a Level 2 charger and other garage loads. See EV charger installation.
A main panel that is full
If your main panel has no open spaces — or your service is too small — a subpanel or a panel upgrade is the fix. We tell you which one makes sense.
From load calculation to passed inspection
Load calculation
We add up what you plan to run and confirm your main panel and service can carry it. If not, we tell you before you spend a dollar on the subpanel.
Permit
We pull the permit with the City of Twin Falls Building Department. Details on our electrical permits page.
Feeder and subpanel
We size the feeder for the load and distance, trench or run conduit as needed, and set the subpanel with separate neutral and ground bars and proper grounding at a detached building.
Inspection
We schedule the city inspection and give you the documentation for your records and your insurer.
Choosing a subpanel size
The right size depends on what you will run today and what you may add later. These are common starting points — your load calculation decides.
| Subpanel size | Common uses |
|---|---|
| 60A | Lights, outlets and small tools in a garage or small outbuilding |
| 100A | Workshop with 240V tools, a hot tub, or a garage with an EV charger |
| 125A–200A | Large shop, barn, ADU or building with heat, welders and compressors |
Wire size, breaker size and conduit all follow from the amperage and the distance from your main panel — voltage drop matters on long runs to a shop or barn.
What affects the price of a subpanel
Subpanel jobs vary more than almost any other electrical project, so we price each one in writing after a look at the site. The main factors:
- Feeder length and route — a subpanel in an attached garage is a short run; a shop 150 feet away needs trenching and conduit.
- Amperage — larger feeders and panels cost more.
- Available space in your main panel — if a service or panel upgrade is needed first, that is quoted separately.
- Surface and soil — concrete, rock and landscaping change trenching time.
- Permit — City of Twin Falls permit fees for typical jobs are listed in our cost guide.
You will always receive a written estimate before work starts.
Frequently asked questions
Can I add a subpanel if my main panel is full?
Often yes — a subpanel is fed by a single breaker in the main panel, so you need one available two-pole space (or a breaker that can be rearranged) and enough service capacity. We confirm with a load calculation. If the main panel or service is the limit, a panel upgrade comes first.
Do I need a permit for a subpanel in Twin Falls?
Yes. A subpanel is permitted electrical work. We pull the permit and schedule the inspection — see Electrical Permits in Twin Falls.
How far can my shop be from the house?
There is no fixed limit, but longer feeders need larger wire to limit voltage drop, which adds cost. We size the feeder for your distance and load.
Why are the neutral and ground separated in a subpanel?
In a subpanel the neutral and ground must be kept separate (bonded only at the main service) so that normal current does not flow on grounding conductors and metal parts. It is one of the most common DIY mistakes and one reason inspectors check subpanels closely.
Can I do a subpanel myself?
A subpanel is licensed, permitted and inspected electrical work in Idaho, and mistakes here create shock and fire hazards. See licensed electrician in Idaho and how to verify a license.
Related services & guides
Shop & Garage Electrical
Electrical for detached garages, shops and pole barns in Twin Falls, Idaho: feeder, trenching, subpanel, 240V circuits, lighting and permit.
Wiring a detached garage or shop →Panel Upgrade
Electrical panel upgrades in Twin Falls, ID. 100A to 400A upgrades, Federal Pacific replacement, Idaho Power coordination. City permit included. Get an estimate.
Electrical panel upgrades →Electrical Permits
Everything about electrical permits in Twin Falls, ID. What requires a permit, City Building Dept fees & process. Tervano Electric pulls permits on every job.
How electrical permits work →Cost Guide
Electrician costs in Twin Falls, ID — panel upgrades, wiring, EV chargers & emergency rates. Written estimates before any work starts. Call (208) 719-5016.
Our electrical cost guide →New Service & Power Pole
New electrical service, power pole and temporary power for Twin Falls County: meter base, panel, trenching and Idaho Power or MVEC coordination.
New electrical service and power poles →EV Charger Installation
Level 2 EV charger installation in Twin Falls, ID. 240V/48A EVSE for Tesla, Rivian & all EVs. Panel check included. Idaho Power rebates available. Permitted.
Level 2 EV charger wiring →Panel Replacement
Federal Pacific, Zinsco & Pushmatic panel replacement in Twin Falls, ID. Licensed electrician, city permit included. Idaho Power coordination. Get an estimate.
Electrical panel replacement →Outlet Installation
GFCI & AFCI outlet installation in Twin Falls, ID. Kitchen, bathroom, garage & outdoor outlets. Licensed electrician, 2023 NEC code. Get an estimate.
Adding new outlets and circuits →Get Your Twin Falls Subpanel Installed Right
Load calculation, permit and inspection handled. Written estimate before work starts.
📞 Call (208) 719-5016 Get an Estimate