How Many Energy Credits Do I Need in Washington State?
Under the 2021 WSEC-R ( WAC 51-11R), your required credit total depends on your building’s conditioned floor area and fenestration (window/glass door) area. The system uses three size tiers, plus a reduced requirement for small additions.
Credit Requirements by Size Tier
| Size Tier | Conditioned Floor Area | Fenestration Area | Required Credits |
|---|---|---|---|
| Small | < 1,500 sqft | < 300 sqft | 5.0 |
| Medium | 1,500–5,000 sqft | Any | 8.0 |
| Large | > 5,000 sqft | Any | 9.0 |
| Addition (small) | 150–500 sqft addition | Any | 2.0 |
Important: The “Small” tier requires both conditions — floor area under 1,500 sqft and fenestration under 300 sqft. If your home is under 1,500 sqft but has 300+ sqft of windows, you fall into the Medium tier (8.0 credits).
Where do the credits come from?
Your total is the sum of two tables:
R406.2 — Fuel Normalization Credits (0–3.0 credits)
You select exactly one option based on your primary heating system fuel type. This credit exists to level the playing field between fuel types. A standard all-electric heat pump earns the maximum 3.0 credits. A gas furnace earns 0.
R406.3 — Energy Credits (variable, up to ~14 total available)
You select options across 7 categories, each with a maximum cap:
- Building Envelope (max 2.5) — windows, insulation, walls
- Air Leakage & Ventilation (max 2.0) — air sealing + HRV
- HVAC Equipment (max 2.5) — furnace/heat pump specs
- HVAC Distribution (max 0.5) — duct location/leakage
- Water Heating (max 3.5) — water heater type and efficiency
- Renewable Energy (max 4.5) — solar PV generation
- Appliance Package (max 0.5) — ENERGY STAR appliances
A typical compliance example
A 2,000 sqft single-family home in Spokane (CZ5, Medium tier, 8.0 credits required):
- R406.2: Heat pump (standard) = +3.0
- R406.3 Option 1.2 (Envelope Tier 2) = +1.0
- R406.3 Option 2.1 (Air leakage ≤2.0 ACH50) = +1.0
- R406.3 Option 5.6 (Electric HPWH NEEA Tier III) = +2.0
- R406.3 Option 7.1 (ENERGY STAR appliances) = +0.5
- R406.3 Option 4.1 (Ducts in conditioned space) = +0.5
Total: 8.0 credits — exactly meets the 8.0 requirement. PASS.
What if I’m confused by the C3 spreadsheet?
The WSU C3 spreadsheet is the official compliance tool. It’s powerful but complex. wsec.ai provides the same R406 calculation in a guided wizard format that shows you exactly where you stand and recommends the cheapest ways to close any credit gap.
Find out your credit requirement in 2 minutes
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