The Corps Wants Solar… But They Won’t Tell You the Size?! Here’s the Catch

By Sean & Doug Reitmeyer — GCExperts. Originally posted on Skool: .

https://gcexperts.com/zoom Summary Harry, a longtime GCExperts client, called in with questions about a Corps of Engineers RFQ for a solar array. Unlike traditional solicitations that specify the system size, this one required the contractor to design a system based on the facility’s stated power usage. That shifts responsibility—and risk—onto the contractor to prove the design meets requirements. Sean walked Harry through the fundamentals of solar system sizing (volts × amps = watts), differences between grid-tie and battery-backup systems, and how to measure real consumption using amp meters and watt meters. Sean emphasized documenting the basis of design by showing calculations tied directly to the loads being powered, so if challenged, the contractor can prove the system matches the stated requirements. The discussion also covered practical considerations: - How solar panels actually charge 12V batteries using ~18V output and charge controllers. - Why contractors must account for amperage when choosing wire sizes. - The role of battery systems, inverters, subpanels, and transfer switches in designing backup systems. - How to translate watts and amp-hours into real-world device runtimes. The key risk Harry identified was the Corps’ tendency to expect “overkill” designs. Sean advised ensuring the design is backed up with measurable usage data, equipment labels, and wattage calculations, so the contracting officer has a clear basis for acceptance early in the process. Key Takeaways - Design-Build Solar Contracts: Some solicitations push sizing responsibility onto contractors—document your math and usage assumptions to avoid disputes. - Watts = Volts × Amps: Core equation for translating power needs into system design. - Load Analysis Is Critical: Use amp meters, watt meters, and equipment labels to add up real usage. - Grid-Tie vs. Battery Backup: Two very different applications; clarify what the government actually wants. - Amp-Hours Define Battery Capacity: Know how long batteries can realistically support loads. - Protect Yourself: Provide a transparent “basis of design” showing how the system meets the stated power requirements.