If you are planning an ADU, converting a garage into a workshop, or adding a Level 2 EV charger in a detached structure, the question that comes up almost every time is whether you actually need a subpanel installation or something bigger. In Camarillo, where ADU construction has picked up steadily since the state loosened permitting rules, this question is worth answering correctly before you get quotes, because it changes both the scope of the electrical work and the price.
Here is how to tell which one you need, what a subpanel actually costs in Camarillo by amperage and location, and what California code specifically requires for ADU and detached-structure electrical work.
Why This Question Keeps Coming Up in Camarillo
Camarillo has seen a steady wave of garage conversions, backyard ADUs, and workshop buildouts over the past few years, driven largely by state-level changes that made ADUs faster and cheaper to permit almost everywhere in California. Older Camarillo neighborhoods with larger lots, particularly around the east side of town and toward Santa Rosa Valley, tend to have more room for a detached ADU or workshop, which is exactly the situation where the subpanel-versus-full-upgrade question matters most.
At the same time, many of these same homes were built with 100-amp electrical service that was perfectly adequate decades ago but leaves little room for a new structure’s electrical needs without either careful planning or a main panel upgrade first.
What a Subpanel Actually Does
A subpanel is a secondary breaker box fed by a single circuit from your main panel. Instead of running eight or ten individual circuits back to the house for a garage workshop or an ADU, one feeder circuit runs to the subpanel, and all the branch circuits, outlets, lighting, and equipment for that space are wired from there.
The advantage is efficiency. A subpanel uses only one or two spaces in your main panel instead of a dozen, and it keeps all the new wiring for the addition organized in one place rather than scattered across your existing panel. For most garage, workshop, and ADU projects in Camarillo, a subpanel is the more practical and often less expensive path compared to running everything as separate long circuits from the main panel.
When You Need a Subpanel vs. a Full Panel Upgrade
These are two different projects that solve two different problems, and it is easy to conflate them when you are getting quotes.
- You need a subpanel if your main panel has enough spare capacity to support one more circuit, and the new space (garage, workshop, ADU) needs its own set of branch circuits.
- You need a full panel upgrade first if your main panel is already near its rated capacity, which is common in older Camarillo homes still running on 100-amp service. In that case, the subpanel gets added after the main service is upgraded, not instead of it.
A licensed electrician can tell you which situation you are in with a load calculation, which looks at your home’s existing circuits, appliances, and planned additions against what your main panel can actually support. Skipping this step is the most common reason a subpanel project stalls partway through, once the electrician discovers on-site that the main panel cannot feed it safely.
What You Can and Cannot Do Yourself
Trenching the feeder run itself is one of the few parts of this project some homeowners handle themselves, since digging a trench to the correct depth does not require a license, only a shovel, a rented trencher, or in some cases a contractor willing to let the homeowner handle that portion separately. Everything else, from running the actual feeder cable to landing wires in the panel to setting the ground rod, needs to be done by a licensed electrician and inspected before it is buried or closed up.
This split can meaningfully reduce cost on a detached subpanel, but it only works if you coordinate directly with your electrician on trench depth and routing before digging, since a trench that is too shallow, too narrow, or in the wrong location will need to be redone. Conduit and direct burial requirements differ, and your electrician will specify which one your project needs based on the feeder cable and local soil conditions.
Subpanel Costs by Amperage in Camarillo
Amperage is the biggest driver of both hardware cost and what the subpanel can actually run once installed.
- 50 to 60 amp subpanel: handles a two-car garage with lighting, outlets, and a standard garage door opener. This is the lightest and least expensive tier.
- 100 amp subpanel: the most common choice for a workshop with power tools, a dust collector, or a small ADU with modest electrical needs.
- 200 amp subpanel: generally required for a full ADU that includes an electric range, an electric water heater, a mini-split system, and an EV charger, since those loads add up quickly under California’s all-electric building trend.
Attached vs. Detached Installation Cost Differences
Where the subpanel lives matters almost as much as its amperage. A subpanel mounted inside an attached garage, right next to or near the main panel, is the simplest and least expensive version of this job. A subpanel feeding a detached garage, workshop, or ADU requires trenching a feeder run underground, which means conduit, a longer 4-wire feeder cable, and a dedicated ground rod at the detached structure itself, since National Electrical Code Article 250 requires separate grounding at a detached structure fed by a subpanel.
Trenching depth and distance both affect price directly. A short run of twenty or thirty feet across a Camarillo backyard costs meaningfully less than a run of eighty or a hundred feet to a detached structure at the back of a long lot, which is common on some of the larger parcels around Camarillo and unincorporated areas like Santa Rosa Valley.
Choosing the Right Equipment
Once amperage and location are settled, the actual subpanel hardware is a smaller decision than most homeowners expect. Square D, Eaton, and Siemens are the three brands most licensed electricians in Ventura County stock and install regularly, and all three are code-approved and widely available if a breaker ever needs replacing years down the line. The bigger equipment decision is usually breaker spaces, not brand: an ADU subpanel that will eventually feed a kitchen, laundry, HVAC, and an EV charger needs enough open slots from day one, since adding a tandem breaker or a sub-subpanel later is a workaround, not a clean solution.
For garage workshops specifically, it is worth flagging any equipment with a motor start-up surge, like a table saw, air compressor, or welder, since that briefly draws more current than its running rating suggests. A subpanel sized only for steady-state loads can trip unexpectedly the first time a compressor kicks on, which is a common and avoidable mistake in workshop wiring.
“The number one thing that turns a simple subpanel job into a bigger one is finding out mid-project that the main panel doesn’t actually have room. That’s why we always run the load calculation first, before anyone commits to a price. It protects the homeowner from a surprise change order halfway through.”
Victor, High Voltage Electrical
ADU-Specific Subpanel Requirements Under California Code
California has made it dramatically easier to build an ADU over the past several years, and construction has followed. More than 80,000 ADUs have been permitted statewide since the first major ADU reform law passed in 2016, and that pace has only picked up as later legislation removed owner-occupancy requirements and capped how much cities can charge in impact fees for smaller units.
The electrical requirements for an ADU are not optional extras. Under current California ADU law, jurisdictions must approve a complete ADU application within 60 days without a discretionary hearing, but the electrical work inside that application still has to meet full code, which for most ADUs means:
- A dedicated subpanel or, for larger ADUs, a full second electrical service sized for the unit’s kitchen, laundry, HVAC, and any EV charging.
- Grounding and bonding at the ADU structure that meets National Electrical Code requirements for a separately fed building.
- Compliance with California’s Title 24 energy code, which affects lighting type, control requirements, and in many cases pushes ADUs toward all-electric appliances rather than gas.
Impact fees are waived entirely for ADUs under 750 square feet, which helps offset some of the electrical cost, but the subpanel or service upgrade itself is not fee-exempt and should be budgeted as part of the ADU’s core construction cost, not an afterthought once the structure is framed.
This is also where separate metering becomes relevant. If you plan to rent out the ADU, a separately metered subpanel makes it possible to bill the tenant directly for their own usage rather than absorbing it into your main utility bill. Not every ADU needs this, but it is a decision worth making before the electrical rough-in, since retrofitting separate metering after the fact means additional utility coordination and cost that is easy to avoid by planning for it up front.
Permit and Inspection Process in Camarillo
Subpanel work in Camarillo, whether for a garage, workshop, or ADU, requires a permit in essentially every case, and skipping it creates a real liability. Unpermitted electrical work is one of the most common issues that surfaces during a home sale inspection, and it can delay or derail a sale entirely if a buyer’s inspector flags a subpanel with no record of a permit or final sign-off.
The typical sequence looks like this: your electrician submits the permit application with the load calculation and a wiring diagram, the city or county reviews and approves it, the subpanel is installed and the feeder run completed, and a final inspection confirms grounding, bonding, breaker sizing, and labeling before the job is closed out. Most straightforward garage or workshop subpanels move through this process in a matter of weeks; ADU-related electrical work often runs in parallel with the broader ADU permit timeline, which can take longer depending on the overall project scope.
It is worth confirming your contractor’s license status before signing anything, which you can do directly through the California Contractors State License Board. A properly licensed contractor pulling the permit protects you twice over: it means the finished work will pass inspection cleanly, and it means the subpanel will not become a red flag on a future home sale the way unpermitted electrical work often does.
Planning Ahead for What You Will Actually Run
The most common regret homeowners have after a subpanel installation is undersizing it. A 60-amp subpanel installed for “just a workshop” often turns out to be too small once a welder, a second EV charger, or a mini-split gets added a year or two later, and upsizing after the fact means redoing the feeder run rather than simply adding a breaker.
Before finalizing amperage, it is worth listing out everything you might reasonably add within the next five years, not just what you need on day one. If an EV charger is even a possibility, sizing the subpanel to support a dedicated 50-amp circuit for it now is almost always cheaper than adding capacity later. High Voltage Electrical’s EV charging team frequently coordinates directly with subpanel installations for exactly this reason, since a garage or ADU subpanel is often the most practical place to feed a Level 2 charger.
If you are still deciding between a subpanel and a full panel upgrade, the safest starting point is a load calculation from a licensed electrician rather than guessing based on what a neighbor’s project cost. Camarillo’s mix of older tract homes and newer ADU-friendly lots means the right answer varies more from property to property than most homeowners expect, and getting it right the first time is what keeps a subpanel project on budget and on schedule.
The projects that go smoothest tend to share one thing in common: the homeowner brought the electrician in before finalizing the ADU floor plan or workshop layout, not after. A quick conversation about what the space will eventually need, not just what it needs on move-in day, is the cheapest insurance against a redo a year or two down the road.
