Research & data

Cali Energy Solar Research

How rooftop solar actually performs in the Los Angeles area: yearly and monthly production per kW, output by system size, how far production drops in winter and how much it changes from year to year. Measured on 89 rooftop systems we monitor over 385 complete system-years, 2019–2025 — not models, not manufacturer claims.

Updated October 7, 2026 · Data through December 2025 · Cali Energy research team · CSLB #1032379 · verify license

Rooftop systems in the production benchmark

385

Complete system-years of measured output

4,437 MWh

Electricity measured

1,456

kWh per kW a year, median result

Solar production & seasonality

Flagship report

Real-World Solar Production in Los Angeles

How much electricity rooftop solar really produces per kW, year by year, and how it compares with the PVWatts model.

1,456 kWh/kW a year385 complete system-yearsCSV

Benchmark + tool

Monthly Solar Production in Los Angeles

The normal range for every month, kWh per day, and a check for your own system.

Jul 163 · Dec 68 kWh/kWCheck your month

Benchmark

How Much Does a 4–12 kW Solar System Produce?

Yearly, monthly, daily and per-panel output by system size, and the size you need for your usage.

6 kW ≈ 8,740 kWh a year10 kW ≈ 14,560

Study

How Much Does Solar Production Drop in Winter?

December versus June on the same systems, and why real roofs fall further below the model in winter.

Dec = 45% of JuneNov–Feb = 23% of the year

Long-term system performance

Study + tool

Why Did My Solar Production Drop This Year?

Year-to-year change on the same systems, checked against NASA sunlight data, and a tool to compare your system with the fleet.

Middle half -6.3% to +2.0%2023: -10.7%NASA sunlight

Study

How Fast Do Solar Systems Lose Output?

Sunlight-corrected output on the same roofs over five to nine years, compared with NREL field data, and the dips every system shared.

−1.3% a year (median)60 systems, 5+ years33% lose under 0.5%/yr

Energy flows & batteries

Measured examples

How Much Solar Does a Home Actually Use?

Where solar went and where electricity came from in six fully metered homes, season by season, and what a daily-cycling battery changes.

Used on site 15–70%From the grid 23–89%

Monitoring & service

Verified cases

What an Inverter Failure Costs, and What a Repair Restores

Production before, during and after verified inverter replacements, and how long the warranty process took.

Restored to 99% of prior level7% of a year lost16 days to new inverter

Market & permits

Public records

Residential Solar Permits in Unincorporated LA County, 2020–2026

How many homes file for solar each month, how many add a battery, how fast permits are issued and how many reach final inspection.

−54% since 2022Battery share 7% → 64%Express: 86–91% same day

Coming next

Batteries: how home batteries are used month by month and season by season.
Monitoring & service: how to tell a monitoring glitch from lost production.

About the data

The data come from the monitoring accounts of real customer systems, recorded month by month by the inverters. We publish only aggregates — medians, ranges and counts — never customer names or addresses. Every study states how many systems and years it uses, what was excluded and why, and the date it was last updated. Aggregated tables are free to reuse under CC BY 4.0 with a link to the study. The permit study is the exception: it uses public permit records from LA County Public Works, not our monitoring data.

Cali Energy is a licensed contractor (CSLB #1032379: B, C-10, C-39) based in Northridge. We design, install and service solar, battery and roofing systems across Los Angeles and Ventura counties.

Projects and service behind the data

The data come from systems like these.

ProjectsSan Fernando Valley solar projectsCompleted installs in the valley where most of the measured systems are.Case studiesHow specific LA projects wentPermits, inspections, roofs and results, project by project.InstallationSolar sized for your roof and usageWe size from 12 months of kWh and your roof’s direction, tilt and shade, not a city average. Terms in writing.ServiceOutput looks low? Ask us to check itSend a year of production and your system size. We compare it with this data and look for shade, offline panels or an inverter fault.

Prepared by Cali Energy, October 7, 2026. Figures describe systems in our monitoring fleet and are not a guarantee of what any specific roof will produce; orientation, tilt, shade, equipment and weather change results. Not engineering, financial or utility advice. See our Content Disclaimer.