Running Power to a Detached Garage or Barn: What's Involved
CC0, via Wikimedia Commons
Running power to a detached garage or barn in North Idaho typically runs $3,500 to $15,000 or more. The spread is wide because the job is really three jobs in one: trenching or overhead line work, a new subpanel at the outbuilding, and permitting through the county or city. A short run to a small shed-sized garage on flat ground lands at the low end. A long run across rocky or root-filled soil to a barn with a 100-amp subpanel and its own well pump or shop equipment pushes toward the high end.
What drives the price
| Factor | Effect on cost |
|---|---|
| Distance from main panel to outbuilding | Trenching and wire cost scale directly with linear feet, often $10 to $25 per foot once labor and materials are combined |
| Soil and terrain | Rocky ground, tree roots, or a slope can double trenching time; hand digging near foundations or septic lines costs more than a machine run through open dirt |
| Overhead vs underground | Overhead is usually cheaper to install but needs a pole and clearance from structures and driveways; underground looks better and holds up to weather but costs more upfront |
| Subpanel size | A 60-amp subpanel for lights and a couple outlets costs far less than a 100 or 200-amp panel sized for welders, compressors, or a future apartment |
| Trench depth requirement | Direct-burial cable rated for underground use still needs to meet minimum depth under code, usually 18 to 24 inches depending on the wire type and whether it is under a driveway |
| Permit and inspection | Bonner and Kootenai county permits add a few hundred dollars and require an inspection before the trench gets backfilled |
| Existing panel capacity | If the main house panel is already full, adding a new circuit for the outbuilding may require a panel upgrade first |
A realistic example
A typical case: a homeowner near Sagle wants power to a 24x30 detached garage sitting about 150 feet from the house, on mostly flat ground with a gravel driveway to cross. The plan is a 100-amp subpanel for lights, outlets, a small heater, and eventually a welder.
The work involves trenching roughly 150 feet, most of it by machine but with some hand digging near the house foundation and under the driveway where a sleeve gets bored in rather than trenched. Direct-burial rated cable or conduit runs from the main panel to a new 100-amp subpanel mounted in the garage, with its own breakers, grounding rod, and disconnect. A permit gets pulled through the county, and an inspector checks the trench depth and grounding before backfill and again after the panel is energized.
All in, a job like this commonly lands in the $6,000 to $9,000 range. Rocky soil, a longer run, or a request for 200-amp service instead of 100 can push it higher. A shorter run with a smaller 60-amp panel and no driveway crossing can come in under $5,000.
Where people overpay
The most common overspend is sizing the subpanel wrong in one direction or the other. Some homeowners install a small 30 or 60-amp panel to save money upfront, then find out two years later they can't run a welder and a heater at the same time without tripping breakers. Digging that trench back open to upgrade wire costs more than doing it right the first time. On the other side, some people oversize to 200 amps for a garage that will only ever hold a lawn mower and a workbench, paying for capacity they will never use.
Skipping the permit is another place people think they're saving money and actually aren't. An unpermitted circuit can complicate a home sale, cause problems with insurance after a fire or damage claim, and in some cases requires the whole thing to be dug up and redone to pass inspection later. The permit fee is small compared to that risk.
The third common overspend is paying for overhead line work when underground would have been the better long-term choice, or the reverse. Overhead is often quoted as the cheap option, but if the run crosses a driveway, a parking area, or anywhere a truck or trailer might need clearance, the pole and height requirements can eat up the savings. A contractor who walks the actual site before quoting will catch this. One who quotes over the phone based on distance alone often won't.
How to get an accurate quote
Get someone out to walk the actual route from the main panel to the outbuilding before you get a number. Have a rough idea of what you'll run out there: lights and outlets only, or a shop with tools, a heater, maybe a future bathroom or apartment. That decides subpanel size, which decides wire gauge, which decides most of the cost. Ask whether the quote includes the permit and both inspections, and ask if they've checked whether your soil or driveway crossing will need hand digging or a bore instead of straight trenching. Sageland Electric has handled outbuilding power for homes, cabins, and small businesses across Bonner and Kootenai counties, and a site visit before quoting is standard practice for a job like this.
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