One of the most common questions from Seattle homeowners considering an ADU is: how much rent will it generate, and when will I break even? Here are realistic numbers based on current Seattle rental market data.
ADU Rental Rates in Seattle and the Eastside (2026)
Studio ADU (350-500 sq ft):
$1,400 to $1,900/month
1-bedroom ADU (500-700 sq ft):
$1,800 to $2,400/month
2-bedroom ADU (700-900 sq ft):
$2,400 to $3,200/month
Mercer Island / Medina premium:
Add 25-40%
Kirkland / Redmond:
$1,900 to $2,800/month for 1BR
ADU Cost vs. Rental Income: Break-Even Analysis
Example: A detached 600 sq ft 1-bedroom backyard cottage in Seattle:
- Total project cost: $320,000 (construction + design + permits)
- Monthly rental income: $2,100
- Annual gross income: $25,200
- Annual net income (after 10% vacancy + maintenance): ~$21,000
- Gross yield: 7.9%
- Break-even: approximately 15 years
A garage conversion ADU has a faster break-even:
- Total project cost: $140,000
- Monthly rental income: $1,600
- Annual net income: ~$16,000
- Gross yield: 11.4%
- Break-even: approximately 9 years
Planning a project?
Wondering what an ADU on your lot would cost?
Send David the address and a few lines about what you want. The first feasibility check is free and usually takes about a day: what the site and the code are likely to allow, and what to check first.
Architect since 1996, member of the AIA and NCARB. Three Masonry Excellence Awards for commercial projects; the Carr residence was featured in Above The Lake and Lux magazines.
Additional Financial Benefits
- Property value increase: ADUs typically add $200,000-$400,000 to Seattle home values
- Multi-generational use: avoiding senior care facility costs for aging parents
- House hacking: offset mortgage with rental income
Piper Cole Architects designs ADUs that maximize rental income through smart layouts and finishes. See our ADU design service or contact us for a free feasibility check. Call 425-753-6452.
Related reading: what an ADU is, the complete guide.
Authoritative sources
Regulatory requirements referenced in this guide are set by the official agencies below. Rules change, always confirm current requirements with the source:
