System Monitoring and Operating Mistakes

A correctly installed solar energy system can still lose most of its savings if it is operated incorrectly or left unmonitored. This document covers the gaps that the original infographics left open: specifically what to monitor and the common operating mistakes that drain savings.

For: handover and maintenance technicians, sales staff guiding customers through the app, and system owners who want to operate their system correctly.

Quick summary

A well-performing system needs consistent monitoring through the app, tracking three core flows (generation, consumption, and grid exchange), along with battery state-of-charge and any active alarms.

The energy management system coordinates these flows according to a charge-discharge schedule, maintains a minimum backup reserve for outage protection, and limits reverse export to the grid to comply with regulations. The current sensor at the grid connection point is the system’s eyes.

A significant portion of savings is lost due to simple operating mistakes: discharging the battery at the wrong hours, charging from the grid at peak-price periods, letting surplus energy export instead of storing it, or failing to update time windows when the tariff changes.

What to monitor

Monitoring enables early fault detection and confirms the system is delivering expected savings. There are several core metrics to track through the manufacturer’s app.

The three fundamental energy flows are solar generation, load consumption, and grid exchange, covering both import and export. For systems with a battery, also track the battery’s state-of-charge and charge-discharge power, as well as the energy source flowing into the battery (solar or grid). Equally important are alarms (such as generation drops, inverter faults, loss of connectivity, or battery errors), so a technician can be called promptly.

The energy management system, known as the EMS, is the component that coordinates these flows according to a charge-discharge schedule, maintains a minimum backup reserve for power-outage scenarios, and limits reverse export to the grid to meet regulatory requirements. The current sensor installed at the grid connection point measures bidirectional current flow; this is the basis on which the EMS calculates self-consumption and controls the anti-reverse-export function, as discussed in Chapter 04.

Common operating mistakes

Many systems lose money not because of poor equipment but because of incorrect settings and operation. The most frequent errors and their fixes are listed below.

The first mistake is discharging the battery at the wrong hours (for example, discharging during off-peak or mid-peak periods instead of reserving stored energy for peak-price evening hours), wasting the most valuable discharge cycles. The fix is to set the discharge window to align precisely with peak-price hours according to the tariff schedule.

The second mistake is charging the battery from the grid during high-price hours, caused by an incorrectly set forced-charge window. Grid charging should only occur during off-peak periods when the price differential is sufficient to offset round-trip efficiency losses.

The third mistake is exporting surplus energy to the grid instead of storing it, even though regulations cap reverse export at 20 percent and compensate it at a low rate. Midday surplus should be stored in the battery for evening use, as analyzed in Chapters 03 and 04.

The fourth mistake is oversizing the solar array beyond the system’s own-use capacity and the export cap, causing generation above that ceiling to be curtailed. System design should target load plus battery rather than aiming to maximize export.

The fifth mistake is setting the backup reserve level too high (leaving insufficient usable battery capacity to cover the full peak-price window) or too low, leaving no energy available during a grid outage. This level should be calibrated to actual backup needs.

The sixth mistake is failing to update time windows when the tariff changes. Peak-price hours have shifted to the evening under the latest regulatory decision, so a system still running on the old schedule will miss the new high-price window. The charge-discharge schedule must be updated after every tariff revision.

The seventh mistake is ignoring seasonal variation in northern Vietnam: building expectations based on summer irradiance and then falling short in the low-sun winter and spring months. Generation estimates should use location- and season-specific peak sun hours (PSH) as described in document 05-02.

The eighth mistake is not monitoring at all, allowing generation drops or connectivity losses to silently erode monthly savings for extended periods without anyone noticing.