The question that decides the job is not how many amps you want out there — it is how far away it is. Why distance sizes the wire, sub-feed versus a new service, and what to get right before the trench closes.
The question people ask is “can I get 100 amps out to the new shop?” The question that actually decides the job is “how far away is it?”
On a town lot, running power to a detached garage is a short job and the wire size falls out of the breaker size. On an acreage, where the shop sits two hundred feet from the house and the barn is further again, distance stops being a detail and becomes the thing that sizes everything. Get that wrong and you end up with a shop that has the right breaker and still cannot run a welder properly.
Two separate things govern conductor size, and people only think about the first.
Ampacity is how much current a conductor can carry safely without overheating. That is the number most people have in mind, and over a short run it is usually what decides the size.
Voltage drop is how much voltage you lose getting to the far end. It climbs with distance and with current. Over a long run it becomes the governing factor, and the conductor ends up noticeably larger than ampacity alone would suggest.
The practical consequence: the feeder to a shop a couple of hundred feet out is sized by the length of the run, not by the breaker on the end of it. Sizing it from an ampacity table and nothing else is the single most common way these installations disappoint.
It is worth saying plainly: none of this shows up on day one with a drill and a radio. It shows up the first time you use the shop for what you built it for, by which point the trench is closed.
Two ways to get power out there, and the right answer depends mostly on what your existing service has left in it.
A feeder from the main panel out to a sub-panel in the shop. Usually cheaper, no second meter, no utility involvement.
The catch is that the shop is now sharing whatever capacity the house service has. If the house is on an older service already carrying heat, water, a well pump and everything else, adding a shop with a welder and a compressor may not leave much room. That is a load question worth answering honestly before the trench rather than discovering it in February.
Its own meter and its own capacity, fed from the utility. Costs more up front and involves the distribution utility, but it does not eat into the house service and it suits a shop that is genuinely going to work.
Whether it makes sense depends on what the utility can bring and what they charge to bring it, which varies entirely with your location and what is already on the line. It is one phone call to find out, and it is worth making that call before committing to the other route.
The cheapest amps you will ever buy are the ones that go in the trench the first time.
Worth sizing for what the building will eventually hold, not what you are putting in it this year:
Upsizing a feeder later means a second trench. Upsizing it while the first trench is open costs the difference in wire.
The part that looks simple and holds most of the regret.
A detached building fed from another building is not just a longer circuit. A few things change at that end.
Specifics on all of the above depend on the installation and are worth confirming against the current code and your inspection authority.
The cheapest time to do anything in a shop is before it is full of benches and machines.
Lighting and layout work is covered under shop and garage electrical.
A feeder to a new building, a sub-panel and the circuits inside it is installed electrical work and generally requires a permit, with inspection by the authority having jurisdiction. Underground work gets inspected before it is backfilled, which is another reason the sequence matters — burying it first and asking afterwards is how a trench gets opened twice.
There is no single distance. It is the combination of distance, the current you want at the far end and the conductor size you are willing to pay for. Long runs are entirely workable — they just need to be sized for the length rather than for the breaker, and that calculation is worth doing before anyone buys wire.
Often yes, and it is a real saving on a long run. The things to agree first are the route, the depth, what goes in it and when it gets inspected, because backfilling before inspection means opening it again. Book locates before the machine arrives.
It is a legitimate method and it is used constantly. The question is whether you would rather spend more now for conduit and keep the ability to pull new conductors later without a second trench. On a long run to a building you expect to add load to, that flexibility is usually worth the difference.
Sometimes, and it is worth measuring before assuming the worst. Voltage under load at the shop panel compared with at the house tells you quickly whether you are looking at voltage drop on the feeder or at something local like a connection. If the feeder is genuinely undersized, the options are a larger feeder or reducing what you ask of it.
A detached building generally needs its own grounding electrode, yes — the house having one does not cover it. This is one of the more frequently missed items when a feeder is run by someone without an electrical ticket.
The useful time to involve an electrician is while the building is a plan and the trench is a line on the ground. Measurements, a realistic load, and a decision between a sub-feed and a new service take one visit and save the expensive version of this job.
Call 403-872-8698 or send the details through the service request form. Distance from the panel and a photo of your existing service are the two things that move it forward fastest.
Related work is covered under panels and equipment power, agricultural electrical and farms and acreages, with local detail on the Red Deer County page.
Grasse Electric serves Red Deer, Red Deer County, Blackfalds, Sylvan Lake, Penhold, Springbrook, Innisfail, Lacombe, Ponoka and Morningside.
Written by Todd Grasse, Red Seal Journeyman Electrician, Grasse Electric — Red Deer, Alberta. Published October 21, 2026.
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