Solar Monitoring: Technical Info

Verifying Production

How do I know my system is working properly?

When Your Energy Solutions provided you an estimate of total system production, we factored in your  roof direction, pitch, your home’s location, and sunlight measurements. You may compare our initial production estimate to what is displayed on the monitoring portal. These numbers will never be the same because weather constantly change.

Each solar installation is unique. Two homes next door to each other with identical solar equipment can produce different amounts of power because of differences such as roof pitch, roof angle, and different levels of shade.

With Enphase microinverters and SolarEdge optimizers, each panel is individually optimized. Variance in production between panels is normal. It is best to view your solar system’s production as a whole rather than a sum of its parts. This is what our production guarantee does.

Peak Production

Let’s say you ordered 22 LG 300 watt panels. This creates a 6.6 kilowatt DC system. However, your system’s production will not peak at 6.6 AC kilowatts.

Each panel is tested in the lab, tested free of dust, dirt, bird droppings, leaves, and shade. For an LG 300 panel, the rating is 300 watts DC. This is the STC (Standard Test Condition) rating.

Because such perfect conditions don’t apply to the “real world”, the California Solar Initiative tests each panel under the best possible “real world” conditions as to determine the PTC (Photovoltaic Test Condition). The difference is approximately 10% less. For LG 300s, the PTC is rated at 273.5 watts DC each.

Factors for the best possible “real world” conditions include:

  • Panels having the ideal roof direction
  • Panels having the ideal roof pitch (angle)
  • The season is ideal (spring/summer) when the sun’s irradiance strongest

It is rare for a typical roof top solar system to have these ideal conditions because roof pitch and roof angle are already determined by the existing roof.

In addition, solar panels produce electricity in Direct Current (DC), while the grid and buildings are wired in Alternating Current (AC). Your inverter converts the DC power into AC power. However, this conversion results in power loss. This final number is then reported on the monitoring portal.

Your Energy Solutions’ production estimate factors in PTC and DC to AC conversion loss when designing your solar system and when estimating expected solar production.

Day & Month Variance

On a sunny day, solar production looks like a bell-shape curve. Over the course of the day, the power of the sun (irradiance), increases, peaks, then drops. Irradiance is stronger during summer months than the winter months. During the summer months, stronger irradiance, in tandem with with longer days, causes peak production and total solar production to be at its highest.

Panel Level Variance

(Applies only to Enphase Microinverter & SolarEdge Optimizer systems)

Production between individual panels, including those next to each other receiving the same amount of sunlight, will always vary. The simple examination are slight variances in batches of solar panels manufactured. The more obvious reason may be levels of soiling (dust & dirt) not visible to the naked eye.

Roof Orientation Variance

(Applies only to Enphase Microinverter & SolarEdge Optimizer systems)

If you have solar panels installed on two or more sections of roof that face different directions, you can expect different levels of production. Some roof directions are better suited to maximize solar production than others. South is best, then southwest, followed by southeast, west, and east.

Shading

(Applies only to Enphase Microinverter & SolarEdge Optimizer systems)

If one or more panels are significantly underperforming, shade is likely the cause. Even a small amount of shade striking a panel can have a huge impact on that panel’s production. Microinverters and optimizers are designed to work with partial shading as only the individual panels are affected, not the entire array.

To see if shade is the cause of your underperforming panels, view the power production for the panel throughout the entire day. If the panel is performing similarly to adjacent, but experiences a sudden drop in production at a certain time of day while other panels continue producing more power, then shade is the culprit.

The impact of shade is seasonal. For most installation, shade has a greater impact during the winter months than summer months. This is because the angle of the sun changes throughout the year. The sun is lower in the horizon during the winter months, causing shadows to be longer. When we designed your solar system, our site technician performed a shade analysis which was factored into your production estimate.



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