Purpose

This report converts utility, solar-production, and tariff data into a clear view of current electricity cost, solar value, and potential cost-reduction opportunities. Results are classified as Actual Billed, Measured, Modeled, or Screening Estimate so that realized results are not confused with projections.

Analysis window: July 6, 2025–August 5, 2026.

Data Sources Used

Source	Use in This Report
SDG&E utility bills	Actual billed utility cost, billing-period usage, demand charges, and other bill charges
SDG&E interval data	Timing and magnitude of grid purchases and monthly demand peaks
Solar monitoring data	Five-minute AC production used to measure solar output and its avoided bill value
SDG&E tariff schedules	Current-rate replay and alternative-rate comparison
System and project information	Solar investment, PTO date, and system-economics context where available

How Results Are Calculated

Actual Utility Cost is the amount billed by the utility during the analysis period, including energy, demand, and other applicable charges.

Solar Avoided Cost estimates the utility charges avoided because the operating solar system served building load. It is derived by aligning validated solar production with the corresponding utility intervals and applying the applicable bill-charge logic. It includes avoided energy charges, avoided demand charges, and applicable variable bill charges.

Rate-Plan Opportunity replays the same measured load under the current and candidate rate schedules. It is a modeled comparison, not an enrolled or realized bill result.

Operational Demand Reduction, Solar Expansion, and Battery analyses are planning-level screening estimates. They use measured demand timing and defined design assumptions, but require additional interval modeling, operational confirmation, and vendor or utility review before implementation.

Data Quality and Controls

Solar production was evaluated using validated five-minute production records. Incomplete or invalid production days were excluded rather than estimated. No missing production was filled in to improve results.

Demand findings are based on the measured interval record. The report identifies the timing of monthly demand peaks but does not assume that a specific machine, EV charger, or operating process caused a peak unless supporting operational data is available.

Important Interpretation Notes

Actual billed cost and modeled rate-plan cost serve different purposes and should not be treated as interchangeable.
Solar Avoided Cost reflects the value achieved during the analysis period; it is not a guarantee of future utility rates or operating conditions.
Savings opportunities may overlap. Solar expansion, demand shifting, battery dispatch, and rate-plan changes must be evaluated together before their values are combined.
Estimated Savings Since PTO is annualized from the measured operating-period Solar Avoided Cost. It is not a reconstruction of every utility bill since the system received permission to operate.

Source Classification

Classification	Meaning
Actual Billed	Directly taken from utility billing records
Measured	Derived from validated interval and solar-production data
Modeled	Replayed using the same load under a defined tariff or scenario
Screening Estimate	Directional planning estimate requiring further validation