Spark Services Subpanel Installation

Subpanel Installation in California

Feed a garage, a shop, an addition or an accessory unit.

A garage or shop subpanel costs 1,200 to 3,500 dollars in Los Angeles, and most of that is the trench and the feeder run.

The short version

A subpanel keeps ground and neutral separate, unlike the main.
Detached buildings need a ground rod of their own.
Four wires go out to a separate building, not three.
Accessory dwelling units almost always need one.

When a subpanel makes sense

When a part of the property needs several circuits, feeding one larger cable out to a small panel beats running four or five separate circuits. A garage shop, a pool area, an addition or an accessory dwelling unit all fit that shape.

It also puts breakers where the work is, so a tripped circuit in the shop does not mean a walk back to the house.

The rule people get wrong

In the main panel the neutral bar and the ground bar are bonded together. In a subpanel they must be separate, with the neutrals floating on their own insulated bar. A bonded subpanel puts current on the ground wire and on anything metal that touches it.

This is the single most common error in work done without a permit, and it is the first thing an inspector looks for.

Feeding a detached building

A separate structure gets four conductors, two hot, one neutral and one ground, in conduit rated for burial. It also needs its own ground rod or rods, and a way to shut off power at the building.

Trenching depth depends on the conduit used and the local rules. Get the depth right the first time, because the inspector looks before it is covered.

Questions people ask

How big should a garage subpanel be

Sixty amps covers a serious hobby shop. A hundred amps is common when an accessory unit or a car charger is in the plan.

Can I run it in the same trench as water

Often yes with separation and the right conduit. The local inspector is the authority.

Do I need a permit

Yes. New circuits and panels are permitted work everywhere in the county.

Electricians who list subpanels work

Google tells us very little about most businesses, so no listing names this work directly. Almost every electrician in the state does it. Start with the highest rated ones.