How to Run the Washington Energy Code Calculator on a Mac
Why the WSU C3 spreadsheet won't run on a Mac
The C3 is a macro-enabled .xlsm workbook built for Windows Excel. The Visual Basic for Applications (VBA) macros that drive its calculations don't run reliably in Excel for Mac — WSU's own documentation marks it as unsupported on macOS. The web and mobile versions of Excel aren't supported either; they strip macro execution entirely.
You don't need Parallels, Boot Camp, or a borrowed PC
The usual workarounds — buying a Windows PC, spinning up a virtual machine (Parallels or VMware Fusion), or using Boot Camp on older Intel Macs — all mean installing and maintaining a full Windows environment just to fill out an energy code form. That's a significant time and cost investment for a task that should take an afternoon.
Run the calculation in your browser instead
wsec.ai performs the same 2021 WSEC-R compliance calculation — R406 energy credits, Total UA, glazing schedule — as a web app. It runs in Safari or Chrome on macOS, on an iPad, or on a Windows PC. No install, no macros, no Excel license required.
| WSU C3 spreadsheet | wsec.ai | |
|---|---|---|
| Runs on Mac / iPad | No (Windows Excel only) | Yes (any browser) |
| Install required | Desktop Excel + macros | None |
| R406 energy credits | Yes | Yes |
| Output | Excel workbook | WSEC-R compliance documentation |
FAQ
Can I use the WSU C3 calculator on an iPad?
No — it requires desktop Windows Excel. wsec.ai runs in the iPad browser with no install.
Is there a Mac version of the WSU C3 spreadsheet?
No. WSU distributes a single Windows macro-enabled workbook. A web-based tool like wsec.ai is the practical Mac route.
Will a Mac-generated wsec.ai report work for my Washington permit?
wsec.ai produces 2021 WSEC-R compliance documentation that you submit to your local jurisdiction with your permit application.
Try the online C3 calculator
Get started →