Commercial Solar for San Diego Office Buildings: What Owners and Tenants Need to Know

Office buildings are not the most obvious solar candidates — they tend to have smaller roof-to-load ratios than warehouses or schools, and the relationship between building ownership and energy consumption is often complicated by tenant leases. But San Diego office properties face some of the highest commercial electricity rates in the country, and the combination of SDG&E demand charges, time-of-use rates, and available incentives can make solar and battery storage financially meaningful for the right building. The key is understanding what actually drives the economics before you evaluate a proposal.

Who Pays the Electric Bill — and Why It Matters

The first question for any office building solar project is who currently pays the electricity bill. In a single-tenant building where the owner also occupies the space, the answer is straightforward. In a multi-tenant building with gross leases, the owner typically pays utility costs and absorbs the benefit of reduced bills directly. In buildings with net or modified gross leases, tenants may pay their own utility costs, which changes the financial case for the owner considerably.

This is not a reason to rule out solar — but it is a reason to map the lease structure carefully before evaluating a proposal. An installer who does not ask about your lease structure in the first conversation is not doing a thorough job. An independent advisor will work through this with you before any system sizing or financial modeling begins.

Demand Charges and the Case for Battery Storage

SDG&E commercial rate schedules include demand charges — fees based on the highest 15-minute interval of power draw during a billing period. For office buildings, demand peaks often occur in the morning when HVAC systems ramp up and occupants arrive, or during afternoon hours when cooling loads are highest. Solar alone does not reliably reduce demand charges, because the peak demand event may not coincide with peak solar production.

Battery storage paired with solar can address this directly — the battery charges during solar production hours and discharges during demand peak windows, reducing the measured peak and lowering the demand charge component of the bill. Whether this pencils out depends on the specific rate schedule, the building's load profile, and the cost of the storage system. It requires actual interval data from your utility bills, not a generic estimate.

NEM 3.0 and What It Means for Office Buildings

Under NEM 3.0, the compensation rate for solar energy exported to the SDG&E grid dropped significantly compared to prior policy. For office buildings — which tend to consume most of their energy during business hours when solar is also producing — the self-consumption rate is generally higher than for residential properties. That is a relative advantage. But it also means the financial model is sensitive to how accurately the system is sized to match actual consumption patterns.

Oversizing a system for an office building under NEM 3.0 produces excess export that is compensated at low rates, which extends payback and reduces returns. An independent review of the production model in any proposal should verify that system sizing is based on your actual interval data, not a rule-of-thumb estimate.

Roof Condition and Structural Considerations

Before committing to a solar project, it is worth verifying:

• Remaining useful life of the roof membrane — a solar system installed on a roof that needs replacement in five years creates a costly removal and reinstallation problem
• Structural load capacity — older buildings may require engineering review before racking and panel loads can be confirmed
• Rooftop equipment conflicts — HVAC units, skylights, and mechanical penetrations reduce usable roof area and affect system design
• Shading from adjacent buildings or rooftop equipment — a production model that does not account for shading will overstate output

A thorough site assessment should address all of these before a proposal is finalized. If a proposal arrives without a site visit, treat the production numbers as preliminary at best.

What an Independent Review Covers

Solar Power San Diego works with commercial office building owners and property managers in San Diego and Southern California as an independent advisor — with no installer commissions and no financial interest in which project moves forward. We review proposals, production models, lease structure implications, demand charge reduction claims, and contract terms, and we provide written findings before you commit to anything.

If you have received a solar proposal for an office building and want to understand what it actually says before signing, we can help.