Wiring a Duplex, Triplex, or Fourplex: What Changes as You Add Units?

If you’re diving into the world of multi-family real estate—whether you’re converting a large basement into a second unit or building a brand-new fourplex—you’ve probably realized that the electrical needs are a lot different than a standard single-family home.

As you add units, you aren’t just adding more outlets; you’re scaling an entire system. Here is what property owners and investors need to know about the electrical side of “middle housing” development.

How Electrical Service Scales With Unit Count

A standard single-family home usually runs on a 200-amp service. While that’s plenty for one family, it quickly becomes inadequate when you have two, three, or four families all running their ovens, HVAC systems, and dryers at the same time.

When Is Single-Family Service No Longer Enough?

The moment you move from one unit to two, the National Electrical Code (NEC) changes the game. You have to consider:

• Multi-Tenant Metering: Each unit needs its own way for the utility company to track power usage.
• Common Area Lighting: Hallways, stairwells, and exterior security lights must be on a separate “house” circuit so one tenant isn’t paying for the light in a shared space.
• Panel Labeling: Every single breaker must be perfectly labeled. This isn’t just for convenience; it’s a legal requirement to ensure emergency responders can cut power to a specific unit quickly.

Utility-Side vs. Contractor-Side Upgrades

Adding units often triggers a utility-side service upgrade. This means the power company might need to bring a thicker wire from the street to your building. On the contractor-side, your electrician will need to install a much larger “meter pack”—the hub where all the individual meters live.

Sub-Panel Strategy for Multi-Family Properties

In a multi-family setup, you want every tenant to have easy access to their own breakers. You don’t want a tenant in Unit A having to knock on the neighbor’s door in Unit B just because they tripped a kitchen breaker.

Sizing for the Future

When sizing sub-panels for each unit, we don’t just look at today’s needs. We think about the future. Will your tenants want to charge an Electric Vehicle? Will you eventually install mini-split heat pumps? Sizing those panels correctly now prevents a very expensive “do-over” later.

Layout for Clean Billing

A “meter pack” layout allows for tenant isolation. This means if Unit 2 doesn’t pay their bill, the utility company can shut off power to just that unit without affecting the rest of the building. It keeps the billing clean and keeps you, the landlord, out of the middle of utility disputes.

The Power of Proper Labeling

Proper labeling is your best protection as a property owner. Clear, professional labels at the main service and every sub-panel prevent “crossed wires” (where one tenant accidentally pays for another’s water heater) and make maintenance much faster and cheaper for any electricians you hire in the future.

Keeping Your Investment Safe and Profitable

Wiring a multi-family property is a complex job that requires a clear plan from day one. Whether you are building from scratch or converting an existing home, getting the electrical service right ensures your tenants are happy, your billing is accurate, and your property meets all safety codes.

At Electric Avenue LLC, we specialize in helping investors and property owners throughout the Portland metro area, including Clackamas, Multnomah, and Washington County. We’re a family-owned team that understands the unique challenges of local building codes and multi-unit developments.

Planning a multi-family project? If you need a professional to look at your layout, handle the utility coordination, or get your units wired correctly, we’re here to help. Reach out to us for an estimate, and let’s make sure your investment is powered the right way.