ADU & DADU Contractor — King County, WA

Add a Legal Dwelling Unit
to Your King County Property

From permit application to final walkthrough — Prolific handles design-build ADU and DADU projects across Federal Way, Issaquah, Renton, Kent, and greater King County.

$180KAverage ADU Cost (King County)
6–12moTypical Timeline Permit to Move-In
$1,800+Monthly Rental Income Potential
3–5yrAverage ROI Payback Period

What We Build

Every ADU project is custom-designed for your lot, your goals, and King County code.

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Detached ADU (DADU)

A standalone dwelling in your backyard. Most flexible for rental or multigenerational living. Requires setback compliance and separate utility connections.

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Attached ADU

Connected to the primary home via a shared wall. Lower cost than detached, faster permitting. Ideal for in-law suites or long-term rental income.

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Junior ADU (JADU)

Converted from existing interior space — garage, basement, or bonus room. Lowest cost entry point. Limited to 500 sq ft per King County code.

The King County Permitting Process

Prolific handles every step. Most homeowners have never pulled a permit — we've done hundreds.

1

Site & Zoning Review

We verify your parcel's zoning, setbacks, lot coverage, and utility capacity before design starts. Catches 80% of project-killers on day one.

2

Design & Engineering

Architectural plans drawn to King County standards. Structural engineering included where required. Typical design phase: 3–6 weeks.

3

Permit Submission

We submit to King County DPER or the applicable city (Federal Way, Renton, Issaquah, Kent). Electronic submission with full plan set.

4

Review & Corrections

County review typically takes 6–12 weeks. We respond to all correction requests and manage the back-and-forth until permit issuance.

5

Build & Final Inspection

Construction with milestone inspections. Final inspection and certificate of occupancy required before the unit can be rented or occupied.

Cost Ranges for King County ADUs

Rough estimates — every project varies by site, size, and finish level. Free estimate available after a site visit.

ADU TypeSize RangeTypical Cost Range
Junior ADU (JADU)Up to 500 sq ft$60,000 – $120,000
Attached ADU400–800 sq ft$120,000 – $200,000
Detached ADU (DADU)400–1,200 sq ft$160,000 – $320,000

Ready to Add a Unit to Your Property?

Free site consultation. We'll tell you what's possible on your lot before you spend a dollar.

Get Your Free ADU Estimate

Prolific's Differentiator

While We're Restoring Your Home, Let's Make It Better Than Before

Most contractors patch the damage and leave. We use the restoration as a launchpad — pairing insurance coverage with a remodel that upgrades what you had.

Storm + Remodel

Federal Way — Hail Damage + Kitchen Upgrade

Insurance covered the roof and siding. While we had the crew on-site, the homeowners financed a kitchen remodel they'd been putting off for years. One mobilization, two wins.

Water + Addition

Renton — Burst Pipe + Primary Bath Expansion

A burst pipe triggered an insurance claim for the subfloor and drywall. We rebuilt the bathroom larger than it was — same timeline, carrier paid the base, owner paid the delta.

Fire + Rebuild

Issaquah — Garage Fire + ADU Conversion

Garage total loss became a permitted two-car garage with a studio ADU above. Insurance rebuilt what burned. The ADU now generates rental income to offset the mortgage.

Insurance Claim? We Handle Everything.

Your Insurance Company Has Adjusters.
Now You Have Us.

STORM DAMAGE RESPONSEthousands more for homeowners just like you.

EV Charger Installation in King County: 2026 Guide to Costs, Permits & Smart Integration for Eastside Homeowners

Electric vehicles aren’t a “someday” trend on the Eastside anymore — they’re parked in driveways from Issaquah to Kirkland. Puget Sound Energy keeps reporting record EV adoption across King County, and homeowners who used to charge in a parking garage at work are now asking the same question: what does it actually take to install a Level 2 EV charger at home in 2026?

This guide walks through the real-world costs, permit steps, panel upgrade triggers, and design choices that come up on almost every install we do at Prolific Design-Build and Restoration. Whether you drive a Rivian, a Tesla, an F-150 Lightning, or you’re just future-proofing your Sammamish home before the next vehicle purchase, this is the homework worth doing before you buy a charger.

Why Home EV Charger Installs Are Surging in King County in 2026

A few forces are colliding at the same time. Washington state’s clean-vehicle incentives, federal tax credits revived through 2032, and rebates from Puget Sound Energy and Seattle City Light have lowered the out-of-pocket cost of going electric. At the same time, EV pricing has come down enough that mainstream Eastside families — not just early adopters — are switching.

The result: more homeowners across Issaquah, Bellevue, Redmond, Kirkland, Sammamish, and Renton are calling for a Level 2 charger as part of a larger remodel. We see it bundled into garage conversion projects, included in energy-efficient remodel ROI plans, and added during whole-home renovations when the electrical panel is already being touched.

The 2026 design trend everyone keeps mentioning — wellness-forward, low-friction homes — extends to the garage too. Charging your car should feel like plugging in your phone, not running an extension cord across a wet driveway in November.

Levels of EV Charging: Which One Belongs in Your Garage?

Before pricing, it helps to know what you’re buying. EV charging falls into three tiers:

Level 1 (120V Standard Outlet)

This is the cord that comes in the box with most EVs. It plugs into a regular household outlet and adds roughly 3 to 5 miles of range per hour. Fine for plug-in hybrids or homeowners who drive less than 30 miles a day, but painfully slow for a battery-electric vehicle in a typical King County commute.

Level 2 (240V Hardwired or NEMA 14-50)

This is what 95% of King County homeowners actually want. A Level 2 charger runs on a dedicated 240V circuit (the same voltage as your dryer or oven) and adds 25 to 40 miles of range per hour. Most cars can fully charge overnight. Level 2 is the sweet spot for cost, speed, and resale value.

Level 3 (DC Fast Charging)

Forget it for residential. DC fast chargers are commercial-grade, require three-phase power, and cost tens of thousands of dollars. They live at Electrify America stations, not in your Bellevue garage.

EV Charger Installation Cost in King County: 2026 Numbers

Pricing varies dramatically depending on your existing electrical panel, the distance between the panel and your parking spot, and whether trenching or wall fishing is required. Here are realistic 2026 ranges we see across the Eastside:

  • Simple install (panel in attached garage, charger within 10 feet): $900 to $1,800 all-in, including permit and a quality Level 2 charger.
  • Standard install (panel and charger on different walls, 20 to 40 feet of conduit): $1,800 to $3,500.
  • Complex install (panel upgrade required, long runs, detached garage, exterior mount): $3,500 to $8,500+.
  • Detached ADU/DADU charger (separate sub-panel, trenching from main): $5,000 to $12,000+.

The single biggest cost variable is whether you need a panel upgrade. Many older Issaquah and Renton homes still run on 100-amp service. A 48-amp Level 2 charger draws 60 amps on a 240V circuit — meaning the panel needs spare capacity, a load-management device, or a full upgrade to 200 amps.

What a Panel Upgrade Adds

A 100-to-200-amp service upgrade in King County typically runs $2,500 to $5,500 depending on the utility tie-in, meter base, and whether the service entrance cable needs replacement. If you’re already planning a kitchen remodel, an ADU build, or a heat pump installation, bundling the panel upgrade into that scope saves significant money. We discuss similar bundling logic in our project bundling guide.

Choosing the Right EV Charger Hardware

The charger market has matured. In 2026, three categories dominate Eastside garages:

Hardwired Chargers

Brands like Tesla Wall Connector, ChargePoint Home Flex, Wallbox Pulsar Plus, and Emporia EV Charger. Hardwired units allow up to 48 amps (11.5 kW) of charging power, integrate with home energy management, and look cleaner on the wall. Required for outdoor installs in the Pacific Northwest’s wet climate when going above 40 amps.

Plug-In NEMA 14-50 Chargers

Units that plug into a 50-amp 240V outlet (the same kind RV parks use). Limited to 40 amps of continuous charging, but portable — you can take the charger with you when you move. Code in Washington requires GFCI protection on these circuits, which has increased install cost slightly under the 2023 NEC adopted statewide.

Smart / Networked Chargers

The 2026 trend is connectivity. Wi-Fi chargers let you schedule charging during off-peak hours (Puget Sound Energy’s time-of-use rate is meaningfully cheaper overnight), monitor energy use, share access with family members, and prepare for vehicle-to-home (V2H) backup power when supported by your vehicle.

Permits, Inspections & King County Code in 2026

Yes, you need a permit. No, it doesn’t need to be painful when it’s done right.

An EV charger install in King County requires an electrical permit through Washington Labor & Industries (L&I) for unincorporated areas, or the local jurisdiction in incorporated cities like Bellevue, Issaquah, Sammamish, and Kirkland. Permit fees typically run $90 to $230 depending on the jurisdiction. A licensed electrical contractor pulls the permit, performs the install, and schedules the inspection.

For homeowners curious how local permitting works in adjacent project types, our Issaquah permits homeowner guide walks through timelines and document checklists you’ll see again on an EV install.

Key 2026 code points to know:

  • GFCI protection required on plug-in NEMA 14-50 outlets per the 2023 NEC.
  • Continuous load rule (NEC 625): the breaker and conductor must be sized at 125% of the charger’s continuous draw.
  • Outdoor / wet location chargers must be rated NEMA 4 or better — a real consideration for King County’s nine-month rainy season.
  • EVSE listing: the charger must be UL-listed (or equivalent) for the install to pass inspection.
  • Service capacity calculation: an electrician must perform a load calculation to confirm your existing panel can handle the new circuit before the permit is issued.

Rebates, Tax Credits & Utility Programs Eastside Homeowners Are Using in 2026

Stack these where you qualify:

  • Federal 30C Tax Credit: 30% of the install cost, up to $1,000, available through 2032 for residential EV charger installations in eligible census tracts.
  • Puget Sound Energy “Up & Go Electric” rebates: qualifying customers can receive rebates on Level 2 charger purchases and panel upgrades. Income-qualified programs offer enhanced incentives.
  • Seattle City Light EV charger rebates (for SCL service territory in parts of north King County).
  • Time-of-use rate plans: not a rebate, but PSE and SCL both offer discounted overnight rates for EV owners that can cut charging costs by 30%+.
  • Washington state sales tax exemption on qualifying EV vehicles continues — separate from the charger, but worth knowing.

Programs change. Confirm current incentives before you sign a contract. We’ll often help homeowners pull the latest rebate forms during the design phase.

Garage Integration: Where the Charger Should Actually Go

The cheapest install isn’t always the smartest one. We see homeowners regret charger placement more than almost any other remodel decision because the car is parked next to it for the next ten years.

A few placement principles we use on every Issaquah, Bellevue, and Sammamish install:

  • Match the car’s charge port location. Tesla and Rivian put the port on the driver’s-side rear. Ford and Hyundai vary. Walk through with the car parked before you commit to a wall location.
  • Mount height: 42 to 48 inches from the floor for most adults. Lower if the homeowner uses a wheelchair — we cover this in our aging-in-place modifications guide.
  • Cable length: 18 to 25 feet covers nearly any two-car garage. Don’t buy 25 feet of cable to clutter a small space.
  • Future-proof for a second EV. If your panel has capacity, run conduit for a second circuit even if you’re only installing one charger today. The marginal cost during the first install is small; opening the wall again is not.
  • Outdoor protection: if the charger is wall-mounted on an exterior wall or a carport, choose a NEMA 4-rated unit and install a small drip edge above it. The Pacific Northwest punishes anything left exposed.

Designing Around the Charger

For homeowners working on a larger garage or ADU project, the EV charger isn’t a separate decision — it’s part of the electrical and storage layout. Concealed conduit, a dedicated sub-panel for the garage, and tidy cable management read as the same kind of streamlined craftsmanship that’s defining 2026 design overall. The goal is the charger feels like it was always part of the house, not a $1,500 box stapled to drywall.

Combining EV Charging with a Garage or ADU Project

Many of our King County clients are tackling EV charging during a larger build because the wall is already open, the panel is already being touched, or the trench is already dug.

Common bundles we’ve completed in 2026:

  • Garage conversion + Level 2 charger: the panel upgrade serves both the new ADU electrical load and the EV charger.
  • DADU build + 100-amp sub-panel: we run a single trench from the main panel to the DADU, terminating in a sub-panel that powers the unit and a dedicated EV circuit at the parking pad.
  • Whole-home electrification: heat pump, induction range, heat-pump water heater, and EV charger together. This typically requires a 200-amp service and load-management hardware, but earns the largest stack of utility rebates and federal credits.
  • New roof + solar + EV charger: we coordinate the EV install with the solar interconnection so a single permit and inspection cycle covers both.

Common Mistakes Eastside Homeowners Make (And How to Avoid Them)

From a decade of restoration and remodel work across King County, here are the regrets we hear most:

  • Buying the cheapest plug-in charger for an outdoor install. Six months later, GFCI nuisance trips and corrosion show up. Hardwired NEMA 4 units are worth the small premium.
  • Skipping the load calculation. A charger that “works” on a 100-amp panel in summer can trip the main breaker the first time the heat pump and dryer run together in January.
  • Hiring an electrician without a permit. Unpermitted electrical work creates real headaches at resale and can void homeowner’s insurance claims if a fire is traced back to the install. We touch on this risk in our piece on documenting property damage and insurance claims.
  • Ignoring future EVs. Two-EV households will be the King County norm by 2028. Sizing the conduit and panel for a second charger is the cheapest insurance you can buy.
  • Mounting the charger in the wrong spot. The cord becomes a tripping hazard, the car parks awkwardly, and snow piles drip onto the unit. Walk it through before drilling.

The Prolific Process for EV Charger Installs in King County

Here’s what working with us looks like, start to finish:

  1. Site visit and load calculation — typically 30 to 45 minutes at the home. We confirm panel capacity, charger placement, and conduit routing.
  2. Fixed-price proposal — no hourly surprises. The proposal lists the charger model, conduit run, breaker, and permit fee.
  3. Permit pull — handled by our licensed electrical contractor.
  4. Install — most simple installs are completed in a single day. Panel upgrades or trenched DADU runs take 2 to 4 days.
  5. Inspection — scheduled with L&I or the local jurisdiction. We meet the inspector on site.
  6. Walkthrough — we set up the charger app, schedule overnight charging on your time-of-use rate, and walk you through the warranty.

If your project is larger — a garage rebuild, an ADU, or a whole-home electrification scope — we run the EV charger as one piece of an integrated design-build plan, not a one-off electrical visit.

Ready to Plug In? Talk to a King County EV Charger Pro

If you’re weighing a charger install for your home in Issaquah, Sammamish, Bellevue, Redmond, Kirkland, Renton, or anywhere else in King County, we’d love to walk your garage with you and put real numbers on paper. Prolific Design-Build and Restoration is a Black-owned and Latino-owned, licensed and insured contractor headquartered in Issaquah and serving the entire Eastside.

Call (425) 800-4775 or visit our contact page to schedule a free site visit. We’ll bring a load calculator, charger samples, and the latest rebate paperwork — and we’ll answer the questions your dealership couldn’t.


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Prolific Design-Build & Restoration — Federal Way, WA

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