Glossary
Solar & energy glossary
Plain, accurate definitions of the terms that come up when you own solar in Pakistan — no jargon, no fluff.
- Net metering vs net billing
- Net metering credits exported solar units against imported ones almost one-for-one; net billing instead buys your exports at a low rate while you buy grid power at the full retail tariff. Pakistan moved new solar consumers from net metering to net billing in February 2026, which makes self-consumption far more valuable than exporting.
- Solar string
- A group of solar panels wired in series so their voltages add up; the string is the level at which most solar faults actually occur. Because a string is a chain, its output is limited by its weakest panel or connection — which is why a single weak string can quietly cut output while the plant total still looks normal.
- Soiling
- The build-up of dust, dirt, and smog on solar panels that blocks light and reduces output until the panels are cleaned. In Lahore, peer-reviewed measurements put soiling losses at roughly 0.8% of output per day at typical tilt in the dry season — among the highest rates recorded anywhere — so regular cleaning matters.
- Panel degradation
- The slow, permanent loss of a solar panel’s output as it ages, typically a median of about 0.5% per year across decades of field data. Degradation is normal and expected, so a few percent lower output on an older system is not a fault — it is the baseline you measure real problems against.
- Performance ratio (PR)
- A standard measure of how much of a solar system’s theoretical output it actually delivers, after real-world losses — a headline health metric defined in IEC 61724-1. Performance ratio lets you compare systems of different sizes fairly and spot underperformance against what the system should be producing.
- Energy management system (EMS)
- Hardware and software that monitors, controls, and optimises how a site uses electricity across every source — grid, solar, and generator. An EMS is the “control and optimise” layer above basic monitoring, and on a multi-source site it answers which source served the load and what each unit cost.
- Solar inverter
- The device that converts the DC electricity from solar panels into the AC electricity a building and the grid use; it also reports basic performance data. The inverter is the hardest-working component and a common point of failure — and its own app only sees its own brand, at the plant level.