At a glance
400 Westlake Building is a 268,005-square-foot office building at 400 WESTLAKE AVE N in Seattle, Washington, built in 2022. In its 2025 Seattle benchmarking disclosure it reported an ENERGY STAR score of 100 out of 100 (grade A), a site energy-use intensity of 11.6 kBtu/ft² and 16 tCO₂e of greenhouse-gas emissions. That score is higher than 96% of the 378 scored office buildings in Seattle.
Seattle Energy Benchmarking Ordinance (SMC 22.920) · reporting year 2025
Benchmarking record
| Field | Value |
|---|---|
| ENERGY STAR score | 100 (band A) |
| Site EUI | 11.6 kBtu/ft² |
| Source EUI | 32.6 kBtu/ft² |
| GHG emissions | 16 tCO₂e |
| GHG intensity | 0.1 kgCO₂e/ft² |
| Electricity | 836,914 kWh |
| Gross floor area | 268,005 sq ft |
| Source record | seattle:51984:2025 |
The disclosure history
Year over year
| Year | Score | Δ | Site EUI | GHG emissions |
|---|---|---|---|---|
| 2025latest | 100 | +2 | 11.6 kBtu/ft² | 16 tCO₂e |
| 2024 | 98 | 14.7 kBtu/ft² | 20 tCO₂e |
Compliance context
Seattle Energy Benchmarking Ordinance (SMC 22.920)
Seattle's Building Emissions Performance Standard (adopted 2023) applies to buildings over 20,000 sq ft: benchmarking verification is due 2027–2030 and initial emissions targets 2031–2035, reaching net zero by 2041–2050, with fines for non-compliance.
Ownership
No owning organisation shown. Names of private individuals in the disclosure are not published here.
Own or manage this building? Claim it to correct the record and get compliance alerts.
Location
- Address
- 400 WESTLAKE AVE N
- City
- Seattle
- State
- Washington
- ZIP
- 98109
- Coordinates
- 47.62237, -122.33805
Within ~1 km
Nearby benchmarked buildings
Office · 1,599,394 sq ft
- Day 1 Tower And Spheres (Amazon)score 93
Office · 1,599,230 sq ft
- Onni South Lake Unionscore 77
Multifamily Housing · 1,546,084 sq ft
- Amazon Doppler Buildingscore 90
Office · 1,496,961 sq ft
- Insignia Condosscore 47
Multifamily Housing · 1,464,631 sq ft
- Hyatt Regency Seattlescore 82
Hotel · 1,400,666 sq ft
See also: most efficient in Seattle · biggest emitters
How does 400 Westlake Building compare with other office buildings in Seattle?
The latest disclosures cover 497 office buildings in Seattle, out of 3,871 buildings citywide. 400 Westlake Building's ENERGY STAR score of 100 compares with an average of 76 across the 378 that report a score; it scores higher than 96% of them. Its site EUI of 11.6 kBtu/ft² is about 74% below the average of 44.8 kBtu/ft² — it uses less energy per square foot than the typical building in that group. Its emissions intensity of 0.1 kgCO₂e/ft² is about 90% below the group average of 0.7 kgCO₂e/ft².
At 268,005 sq ft, it is about 36% above the average floor area of 196,452 sq ft for those buildings. It was built in 2022, 57 years later than the group's average year built (1965). Across all 24 jurisdictions BuildingCensus covers, the 15,264 office buildings average an ENERGY STAR score of 73 and a site EUI of 59.3 kBtu/ft².
How has 400 Westlake Building's energy performance changed over time?
BuildingCensus holds 2 Seattle disclosures for 400 Westlake Building, covering report years 2024–2025. Its ENERGY STAR score went from 98 in 2024 to 100 in 2025 (+2 points). Site EUI moved from 14.7 kBtu/ft² (2024) to 11.6 kBtu/ft² (2025), a 21% decrease. Reported emissions went from 20 tCO₂e to 16 tCO₂e over the same span (down 18%).
What does an ENERGY STAR score of 100 mean?
ENERGY STAR scores run from 1 to 100 and are computed by the EPA's Portfolio Manager as a percentile against similar buildings nationwide, adjusted for climate, size and use: 100 is the top of the scale. BuildingCensus bands the score into report-card grades; 100 falls in band A — high performer (85–100). Scores of 75 or higher meet the threshold for ENERGY STAR certification; certification itself is a separate, verified application that the disclosure does not record. In Seattle, 69% of scored buildings are at 75 or above.
Site energy-use intensity (EUI) is the energy a building uses on site in a year divided by its floor area, in thousand Btu per square foot — lower is more efficient. 400 Westlake Building's 11.6 kBtu/ft² across 268,005 sq ft works out to about 3.1 billion Btu (911 MWh-equivalent) in 2025. Its source EUI of 32.6 kBtu/ft² also counts the energy lost generating and delivering that power, which is why it is higher. The disclosure also reports 836,914 kWh of electricity for the year.
Which law requires 400 Westlake Building to report its energy use?
400 Westlake Building reports under the Seattle Energy Benchmarking Ordinance (SMC 22.920), the legal basis of Seattle's Building Energy Benchmarking program, which publishes each covered building's annual benchmarking results. The record shown here is the report-year 2025 disclosure (source record seattle:51984:2025). Seattle's Building Emissions Performance Standard (adopted 2023) applies to buildings over 20,000 sq ft: benchmarking verification is due 2027–2030 and initial emissions targets 2031–2035, reaching net zero by 2041–2050, with fines for non-compliance.
More office buildings in Seattle
- PLAZA 600 BUILDING· 265,851 sq ft · score 81 (B)
- Amazon- Unicorn· 254,218 sq ft · score 62 (C)
- 3101 Western (Formerly Airborne Bldg)· 253,103 sq ft · score 3 (D)
- World Trade Center North· 251,044 sq ft · score 100 (A)
- Fremont Lake Union Center - Plaza Bldg· 243,334 sq ft · score 98 (A)
- West Tower· 241,875 sq ft · EUI 28.6 kBtu/ft²
- Office buildings in Seattle· 497 benchmarked
- All Seattle benchmarked buildings· Seattle Energy Benchmarking Ordinance (SMC 22.920)
- Most efficient large buildings in Seattle
- Least efficient large buildings in Seattle
- Biggest emitters in Seattle
Frequently asked questions
What is 400 Westlake Building's energy grade?
400 Westlake Building scores 100 out of 100 on ENERGY STAR — band A, high performer (85–100) — in its 2025 Seattle disclosure. Scores are national percentiles against similar buildings; 75+ qualifies for ENERGY STAR certification.
How much energy does 400 Westlake Building use?
Its 2025 site energy-use intensity was 11.6 kBtu/ft² (32.6 kBtu/ft² source) across 268,005 sq ft, including 836,914 kWh of electricity.
What are 400 Westlake Building's carbon emissions?
400 Westlake Building reported 16 tCO₂e of greenhouse-gas emissions (0.1 kgCO₂e/ft²) for 2025.
Where is 400 Westlake Building?
400 Westlake Building is at 400 WESTLAKE AVE N, in Seattle, Washington 98109. Its coordinates are 47.62237, -122.33805 (latitude, longitude), as published in the Building Energy Benchmarking file.
How big is 400 Westlake Building and when was it built?
400 Westlake Building has 268,005 sq ft of gross floor area, as reported in its 2025 disclosure. The disclosure lists 2022 as its year built. It is classed as office.
Is 400 Westlake Building covered by the Seattle Energy Benchmarking Ordinance (SMC 22.920)?
Yes — it appears in the 2025 Building Energy Benchmarking disclosure, which lists the buildings reporting under the Seattle Energy Benchmarking Ordinance (SMC 22.920).
Working with Seattle building benchmarking records? Pro adds alerts, change history and CSV export ($49/mo); Enterprise adds full national files, the API and an MCP server for AI tools.
About this data
Source: Building Energy Benchmarking (Seattle Energy Benchmarking Ordinance (SMC 22.920)), as published October 2, 2026. See the methodology for how records are matched, cleaned and scored.
Cite as: BuildingCensus, “400 Westlake Building, Seattle, Washington — 2025 benchmarking disclosure”, https://buildingcensus.com/buildings/seattle/400-westlake-building-6ae5fd8e (data as of October 2, 2026).