The Short Version
What WSEC Energy Credits Actually Require
Put simply, the 2021 Washington State Energy Code requires new residential construction to earn a set number of additional energy credits on top of the baseline prescriptive requirements. Specifically, builders choose from options across building envelope, air leakage, HVAC equipment, water heating, renewable energy, and appliance categories, laid out in WAC Table R406.3.
Notably, solar PV sits in the Renewable Electric Energy category (Option 6.1), and it’s usually the cleanest option on the list. It earns credits without changing your envelope assembly, mechanical design, or anything else already locked into your plan set. As a result, a typically-sized 4–6 kW residential array earns up to 4.5 credits, which covers most homes’ additional requirement in one scope.
Cost Comparison
Solar Is the Lowest Cost Per WSEC Credit
In fact, most builders size a 6–10 kW system, earning more credits than required while giving buyers a meaningful, visible energy story.
Getting Started
What We Need to Run Your WSEC Review
Project address or lot
Plan set or roof/elevation drawings
Credits still needed to satisfy code
Target construction timeline
Beyond the Credit
The Rest of the WSEC Process
Permitting & AHJ Coordination
Seattle, Bellevue, and Kirkland each handle solar permits a little differently. We track every AHJ’s requirements and handle this end-to-end on every project.
See the Permitting Guide →Utility Interconnection
PSE, Seattle City Light, and SnoPUD all have their own interconnection paperwork and timelines. We manage the applications directly for every lot.
See the Utility Coordination Guide →Rough-In & Trim Sequencing
Conduit routing, panel penetrations, and inspection sequencing need to happen at the right point in the build.
See the Rough-In & Trim Guide →More Builder Resources
Region-Specific Guides
Common Questions
WSEC Builder FAQ
Credit Basics
How do WSEC energy credits work for new homes in Washington?+
In short, the 2021 Washington State Energy Code requires new residential construction to earn a set number of additional energy credits beyond the baseline prescriptive requirements. In practice, builders choose from options across building envelope, air leakage, HVAC, water heating, renewable energy, and appliance categories in WAC Table R406.3. Solar PV is one of the renewable energy options, and often the most straightforward to size and document.
Can solar panels count toward WSEC energy credits?+
Yes, solar PV falls under the Renewable Electric Energy category of Table R406.3 (Option 6.1). In short, a properly sized system can satisfy some or all of a home’s additional credit requirement in a single scope, without touching the building envelope, HVAC equipment, or water heating systems your design is already locked into.
How many WSEC credits can I get from solar?+
Overall, a typical 4–6 kW residential solar array can earn up to 4.5 energy credits under WSEC Table R406.3, enough to satisfy most homes’ additional credit requirement outright. Then, exact credit value depends on system size and is calculated using PVWatts or an approved equivalent, which we handle as part of your WSEC review.
Cost & Next Steps
What’s the most cost-effective WSEC compliance strategy?+
Clearly, solar PV is typically the lowest cost per credit of the standard compliance options, often $3,900 or less per credit compared to $4,500–$6,000 for envelope, air-sealing, or heat pump upgrades. Because it earns credits without changing your building envelope or mechanical design, it’s usually the easiest option to add late in the plan-set process too.
What does Solphos need to run a WSEC review?+
Send us the project address, your plan set or roof/elevation drawings, and how many credits you still need to satisfy code. Then, we’ll return a sized system, credit count, and fixed price, typically within a few business days.
Sources: WAC 51-11R-40621, Table R406.3 · WSU Energy Program WSEC-R 2021 Forms · Seattle SDCI Tip 420
Submit Plans for a WSEC Review
We’ll return a sized system, credit count, and fixed price, usually within a few business days.
