Why Is My Solar System Not Producing Enough? A Temecula Troubleshooting Guide

Adrian Marin|Independent Solar Advisor, Temecula CA

Helping Riverside County homeowners navigate SCE rates and solar options since 2020

A solar system in Temecula should produce reliably for 25 years or more. But production problems do happen, and most of them have identifiable causes you can work through systematically before paying for a service call. This guide walks through every common reason a Temecula solar system underperforms, from the simplest fixes you can do yourself to the fault patterns that require a professional diagnostic. It covers how to read your monitoring data, what local environmental factors make Temecula particularly demanding on panels, and how to build a clear picture of what is wrong before you pick up the phone.

How to Read Your Monitoring App and Establish a Baseline

Before diagnosing any specific problem, you need to understand what your monitoring data is actually telling you. The three platforms used by most Temecula solar systems are Enphase Enlighten, SolarEdge mySolarEdge, and the local display on a string inverter such as SMA or Fronius. Each one uses slightly different terminology for the same underlying data.

Current Power is the real-time output of your system right now, measured in watts or kilowatts. On a clear Temecula afternoon in June, a properly functioning 8-kilowatt system should show 7.2 to 8 kilowatts of current power between 10 a.m. and 2 p.m. This number drops to zero at night and follows a bell curve shape throughout the day, peaking around solar noon, which in Temecula falls roughly between 12:30 and 1:00 p.m. Pacific Standard Time.

Production Today is the total energy your system has generated since midnight, measured in kilowatt-hours. This is the most useful number for a quick daily sanity check. A rough benchmark for Temecula: a 1-kilowatt system in good condition should produce about 4 to 5 kilowatt-hours on a clear summer day and 3 to 4 kilowatt-hours on a clear winter day. Multiply by your system size in kilowatts to get a daily production target. An 8-kilowatt system should produce 32 to 40 kilowatt-hours on a clear June day and 24 to 32 kilowatt-hours on a clear December day.

Lifetime Production is the total kilowatt-hours your system has ever generated, which is useful for calculating whether your all-time production is tracking close to the installer's original projection.

To establish a baseline comparison, find the production estimate from your original installer proposal. It should state something like "estimated annual production: 14,400 kWh." Divide that by 12 to get a monthly target of 1,200 kWh. Pull your actual monthly production from your monitoring app for the past 12 months and compare month by month. Production is naturally higher in summer and lower in winter, so comparing July to July and December to December is more meaningful than averaging across seasons.

A normal production curve for a Temecula-area system looks like a smooth hill when graphed over a single day: flat at zero from sunset to sunrise, rising steeply after 7 a.m., peaking between noon and 1 p.m., then declining symmetrically through the afternoon. Any deviation from this shape, such as a plateau in the middle of the curve, a sharp drop at a specific time, or a lopsided curve that peaks earlier or later than solar noon, is a diagnostic signal pointing to a specific problem.

Soiling: Temecula's Unique Panel Contamination Problem

Panel soiling is the most common cause of gradual, steady underperformance in Temecula, and the local environment makes it more aggressive here than in many other Southern California locations. Four distinct contamination sources combine to create a particularly stubborn soiling problem.

Santa Ana wind events move fine desert dust from the high desert and deposit it directly onto panel surfaces. A single Santa Ana event lasting two to three days can coat panels with a thin layer of particulate that reduces transmission of sunlight to the solar cells. This dust is fine enough to not be visible from the ground but measurable in its effect on output.

Wildfire ash is a seasonally concentrated problem from May through November. Ash particles from regional wildfires, including fires in the Palomar Mountain, San Bernardino National Forest, and Cleveland National Forest areas adjacent to Temecula, deposit on panels and create a more adhesive layer than standard dust because ash particles are irregular and tend to lock together when wet by morning dew or light rain.

Hard water oversprayfrom irrigation systems affects panels on homes where sprinklers or drip emitters can reach roof surfaces. Temecula's water supply has elevated mineral content, and repeated wetting and drying from sprinkler overspray leaves calcium and magnesium deposits on panel glass that are very difficult to remove with plain water. These deposits accumulate over months and create a milky haze that reduces panel efficiency measurably.

Bird droppings are concentrated in areas near Murrieta Creek, Temecula Creek, the Santa Rosa Plateau, and neighborhoods with mature oak trees. Bird droppings are particularly problematic for solar panels because they are opaque and create localized shading on individual cells. Due to how solar panels are wired internally, even a small opaque spot can disproportionately reduce output from an entire string of cells if the soiling is not distributed evenly.

Research on residential panels in the Inland Empire region shows soiling losses ranging from 7 to 15 percent of annual production in the absence of any cleaning. That translates to 1,000 to 2,000 kilowatt-hours per year lost on a typical 10-kilowatt Temecula system, which at current Southern California Edison rates represents $200 to $400 in lost electricity value annually.

A simple field test can confirm whether soiling is your problem before you call anyone: wipe one panel clean with a soft cloth and plain water, then compare its output reading in your microinverter monitoring (this works only with Enphase or panel-level monitoring) against adjacent unclean panels over the following week. A consistent 10 to 20 percent output difference between the clean panel and its neighbors confirms that soiling is the primary issue. Professional panel cleaning in Temecula costs $100 to $200 for a typical residential system and typically requires only soft brushes, deionized water, and no harsh chemicals.

Shading: The Most Commonly Overlooked Cause of Unexpected Production Drops

Shading is the most common cause of unexpected production decline in systems that were performing well initially. Solar site assessments at installation time create a shade analysis based on the current environment. That environment changes over time in ways the original assessment did not account for.

Trees are the most frequent culprit. A tree that was 12 feet tall when your panels were installed may now be 20 feet tall and casting shadows across part of your array during morning or afternoon hours, particularly in winter when the sun angle is lower. Temecula's residential neighborhoods include a mix of mature native oaks, fast-growing eucalyptus, and planted landscape trees that can add several feet of height per year under good conditions. A system that performed correctly for three years and then began declining may simply be experiencing new shading from trees that have grown into the panels' solar window.

Other common new shading sources include neighbor construction adding a room or second story adjacent to your property line, a new rooftop HVAC unit or equipment added to your own home after installation, a newly installed satellite dish or telecommunications equipment, and in some cases, overgrown vegetation on adjacent slopes in hillside neighborhoods near Redhawk, Crowne Hill, or the Wine Country areas.

Monitoring data reveals shading through a specific pattern: a production drop that occurs at a consistent time of day rather than randomly. If your monitoring graph shows that production peaks normally until 10 a.m. and then drops sharply before recovering again in the afternoon, a tree or structure to the east is casting a shadow on your panels during that window. If the drop occurs in the afternoon, the obstruction is to the west. If the drop is worst in December and January and improves in summer, the shading source is something that only creates significant shadow at low winter sun angles.

Shading is particularly damaging to string inverter systems because all panels in a string are wired in series. When one panel is shaded, it acts like a restriction in a garden hose and can reduce the output of every other panel on that same string. Systems with Enphase microinverters or SolarEdge power optimizers are significantly more resilient to partial shading because each panel operates more independently. If you have a string inverter system and you identify new shading on even one or two panels, the production impact can be three to five times larger than the shaded area alone would suggest.

Inverter Failure: Reading the Warning Signs

An inverter failure is the most likely cause when your monitoring shows zero or near-zero production on a fully sunny day with no alert from your utility about curtailment and no tripped rapid shutdown. Inverters are the component most likely to fail before panels in most residential solar systems.

String inverters from brands including SMA, Fronius, SolarEdge, and Huawei have an average field lifespan of 10 to 12 years. Systems installed between 2012 and 2016 are now in or approaching the typical inverter replacement window. Most string inverters come with a standard 10-year manufacturer warranty, which can sometimes be extended to 20 years at additional cost at time of purchase. If your system is more than 8 years old and you are experiencing intermittent production issues or complete production loss, inverter age is a serious diagnostic candidate.

String inverters have physical indicator lights that communicate their status. A solid green light indicates normal operation. An amber or orange light typically indicates a warning condition such as a communication error or grid voltage issue the inverter has detected and is managing. A red light or flashing red pattern indicates a fault that has caused the inverter to shut down. The specific fault code displayed on the inverter screen or in the monitoring app tells you which fault triggered the shutdown. Common fault types include isolation fault (often from water intrusion in wiring or junction boxes), arc fault detection (triggered by damaged wiring), and grid voltage out-of-range (caused by utility line issues, not by your equipment).

Enphase microinverters follow a different failure pattern. Because each microinverter is mounted under an individual panel and operates independently, a microinverter failure shows up as one panel going dark in your monitoring while all surrounding panels continue producing normally. This is easy to spot in Enphase Enlighten, which displays a visual grid of each panel's output. If you see one or more dark panels in an otherwise active grid, those microinverters have failed. Individual microinverter replacement costs $200 to $400 per unit installed. Enphase IQ series microinverters carry a 25-year warranty, so a failure on a system under 15 years old is typically a warranty replacement at no charge from Enphase.

Replacement string inverters for residential systems cost $1,500 to $4,000 installed, depending on system size and inverter brand. If your string inverter is 10 or more years old and failing, it is worth evaluating whether to replace it with the same model or upgrade to a more modern unit with better monitoring and potentially a microinverter or power optimizer retrofit if shading has become a factor.

Panel Degradation: Separating Normal Aging from Real Problems

All solar panels degrade over time. The solar cells lose a small amount of efficiency each year due to ongoing exposure to UV radiation, heat cycling, and moisture. This is normal and expected. The relevant question is whether your system's production decline is consistent with normal aging or significantly worse than it should be.

Quality tier-one panels from brands such as LG, Panasonic, REC, SunPower, and Jinko's premium lines degrade at 0.5 to 0.7 percent per year. Most current panel warranties guarantee a minimum of 80 percent output retention after 25 years, which works out to approximately 0.8 percent per year maximum allowable degradation. A system that is 8 years old should produce 94 to 96 percent of its original output from degradation alone. Framed differently, an 8-year-old system that is producing 10 percent less than it did in year one has a 4 to 6 percent production gap that degradation does not explain.

Budget panels from less established manufacturers sometimes degrade faster than warranted rates, but this is only diagnosable by comparing your actual year-over-year production data against the warranted degradation curve. If you have kept records of your annual production since installation, a simple spreadsheet comparison will tell you whether you are within the normal degradation band or running below it.

One form of panel degradation that is invisible to the naked eye but measurable in output is potential induced degradation, or PID. PID occurs when voltage differences between the solar cells and the panel frame cause ion migration within the semiconductor material, reducing cell efficiency. It is more common in budget panels and in systems with certain inverter configurations. PID typically causes a system-wide gradual decline rather than the loss of specific panels, and it can only be confirmed with an electroluminescence camera test that imaging defects in solar cells by applying a current and photographing the resulting light emission.

Microcracks in solar cells can also develop from hail impact, thermal cycling stress, or improper handling during installation. Temecula experiences occasional hail during winter storm events, primarily in December through February, and severe hail can cause both visible and invisible cell damage. A panel with significant microcracking shows up as dark patches or irregular patterns in an EL camera image. EL testing is available from some solar service companies in the Inland Empire for $100 to $200 per system and provides definitive evidence of cell-level damage.

Grid Events, Utility Curtailment, and Rapid Shutdown Faults

Not every production drop is caused by something wrong with your system. Two external causes are common enough in Temecula that they should be ruled out before assuming a hardware problem.

SCE Utility Curtailment

Southern California Edison operates under California Public Utilities Commission rules that allow it to curtail solar export from customer systems during periods of grid stress. Curtailment events typically occur on high-demand afternoons in summer, particularly during heat waves when grid load is near capacity. During a curtailment event, your inverter receives a signal to reduce or stop exporting power to the grid, and your monitoring system will show production dropping to zero or near zero during peak afternoon hours on what is otherwise a clear, sunny day.

The signature of curtailment in your monitoring data is a sharp vertical drop in production at a specific time, often between 12 p.m. and 3 p.m. on summer days, followed by a return to normal production later in the afternoon. Curtailment is legal, it is outside your control, and it does not indicate any problem with your system. If the production drops you are seeing match this pattern and align with extreme heat or grid emergency announcements from SCE, curtailment is the explanation and no service call is warranted.

Rapid Shutdown Faults

Solar systems installed after the adoption of the 2017 National Electrical Code in California are required to include rapid shutdown capability. Rapid shutdown systems allow first responders to de-energize rooftop panels quickly in the event of a fire or other emergency. The rapid shutdown initiator, sometimes called the solar system disconnect or the rapid shutdown switch, is typically a red button or labeled switch located near your electrical panel, near your utility meter, or in some installations at the base of the roof near the module access point. This switch is designed to be easy to find and easy to press. In practice, it can be pressed accidentally during meter reading, during service work on adjacent equipment, or by a child or household member who did not know what it controls. If your system is showing zero production on a clear day with no inverter fault lights and no curtailment event, check this switch first. Resetting it restores normal operation instantly at no cost.

Visual Inspection: What You Can Check Safely from the Ground

You do not need to go on your roof to do a useful visual inspection of your panels. A pair of binoculars and a clear day are sufficient to identify several categories of visible damage from the ground.

• 1.
  Visible soiling patterns. Look for streaking, dark patches, or a general haze across panel surfaces. Heavy soiling is often visible from the ground once you know what to look for. A uniformly dirty panel will have a slightly duller, less reflective surface compared to a clean one.
• 2.
  Cracked or damaged panels. Impact damage from hail, falling branches, or debris can crack panel glass. Visible cracks usually appear as star patterns or linear fractures in the tempered glass surface. A cracked panel is a safety issue in addition to a performance issue and should be reported to your installer promptly.
• 3.
  Discoloration or hot spots. Panels with internal cell damage sometimes show brownish or yellowish discoloration in the cell area visible through the glass. This indicates thermal damage or cell degradation and is a signal to request a professional inspection.
• 4.
  Delamination. In older panels, the encapsulant material between the glass and the solar cells can begin to separate, creating bubbles or cloudy patches visible through the glass. Delamination significantly reduces panel efficiency and is grounds for a warranty claim if the system is still under the manufacturer's product warranty.
• 5.
  Racking and mounting issues. Look for panels that appear tilted, shifted, or sitting at a different angle than surrounding panels. Wind events can occasionally loosen racking hardware, particularly on systems older than 10 years. A tilted panel is a safety concern and a performance issue simultaneously.

Never go onto your roof to inspect panels yourself unless you are a professional with appropriate safety equipment. The risk of a rooftop fall is significant, and walking on panels can crack them or damage underlying roofing material. All close-up panel inspection and any physical work on racking should be done by a licensed solar technician.

Your Production Guarantee: What It Covers and What It Requires From You

Some solar installers include a production guarantee in their contract, particularly when the system is sold on the basis of a specific annual energy output estimate. These guarantees vary significantly in their terms, and understanding yours before you file a performance complaint can save significant time.

A typical production guarantee states that if your system produces less than a specified annual kilowatt-hour total, the installer will provide a payment or credit to compensate for the shortfall. The guarantee period is usually 1 to 5 years, though some premium installers offer guarantees tied to the panel warranty period of 25 years. The guarantee is almost always conditional on system availability, meaning the system must have been operational for the full guarantee period without owner-caused downtime.

Most production guarantees include a requirement that the homeowner maintain the system appropriately, which typically means keeping panels reasonably clean and allowing the installer access for required inspections. If your guarantee requires annual inspections and you have not scheduled them, the installer may dispute a performance claim on the grounds that the maintenance requirement was not met.

If you believe your system is underperforming relative to a contractual guarantee, the process is straightforward: pull 12 months of monitoring data, calculate total annual production, compare it to the guaranteed annual production figure in your contract, and document the shortfall in kilowatt-hours. Contact your installer with that data in writing and request a warranty inspection. Most legitimate installers respond to documented performance shortfalls within 30 days.

Decision Tree: Who to Call and When

Once you have done your initial diagnostic, the next step depends on what you found. Here is a clear decision framework for who handles each type of issue.

The Step-by-Step Process for Documenting and Addressing Underperformance

Following a structured process will make any service call faster and more productive. Here is the recommended sequence.

• 1
  Pull 12 months of monitoring data.Download or screenshot your monthly production totals from Enphase Enlighten or SolarEdge mySolarEdge for the past 12 months. If you cannot access old data, ask your installer to pull it from their system.
• 2
  Find your original production estimate.Locate your installer proposal or final contract. The projected annual production figure is usually listed as a kilowatt-hour amount per year and sometimes broken out by month. If you cannot find it, the production data submitted with your SCE interconnection application is a public record you can request.
• 3
  Calculate the actual versus projected gap.Subtract your actual 12-month production from the projected 12-month figure. Express the gap as a percentage. If the gap is under 10 percent, evaluate whether a particularly cloudy year or significant weather events explain the difference. If the gap is 10 to 15 percent, soiling or minor shading is the most likely cause. If the gap is 15 percent or more, a hardware issue is likely involved.
• 4
  Work through the free checks first.Check your rapid shutdown switch. Inspect panels visually with binoculars. Look for new shading sources. Check your monitoring app for fault codes or alarm notifications. Do the single-panel clean test if you have microinverter monitoring. These steps cost nothing and may resolve the issue.
• 5
  Schedule a professional cleaning if soiling is suspected.If you have not had your panels cleaned in the past 12 months and you are in Temecula, schedule a professional cleaning before calling for a diagnostic service visit. Many apparent performance problems resolve immediately after a thorough cleaning, and the $100 to $200 cleaning cost is a small fraction of the $150 to $300 diagnostic visit fee.
• 6
  Request a diagnostic service visit if the gap persists.Contact your installer or a licensed solar service company and provide the production data you have gathered. Most service companies charge $150 to $300 for a diagnostic visit that covers visual inspection, inverter diagnostic, monitoring data review, and a written report. Ask for the report in writing so you have documentation for any warranty claim that follows.

Frequently Asked Questions