Glossary

PV

Photovoltaic — technology that converts sunlight directly into electricity using semiconductor solar cells.

kWp

Kilowatt-peak — the rated output power of a solar panel or system under Standard Test Conditions (STC: 1,000 W/m² irradiance, 25°C cell temperature). Measures installed capacity.

kWh

Kilowatt-hour — unit of energy. 1 kWh = 1 kW of power sustained for 1 hour. Used to measure actual energy produced or consumed.

MWh

Megawatt-hour — 1,000 kWh. Used for larger energy totals across longer periods.

Irradiance

The power of solar radiation hitting a surface, measured in W/m². Higher irradiance = more potential energy from panels.

GHI

Global Horizontal Irradiance — total solar radiation on a horizontal surface. Used as a reference for site potential.

POA

Plane of Array irradiance — solar radiation hitting the tilted panel surface directly. More relevant than GHI for actual yield calculations.

Specific Yield

Energy produced per unit of installed capacity (kWh/kWp). Normalises production so sites of different sizes can be fairly compared.

Target Yield

Theoretical energy a site should produce based on its location's historical irradiance data. Used as the denominator in PR calculations.

PR

Performance Ratio — measures how efficiently a PV system converts available solar energy into electricity. Formula: Actual Yield ÷ Target Yield × 100. A PR of 80% means the site produced 80% of its theoretical maximum. Losses come from temperature, wiring, inverter inefficiency, downtime, and soiling.

Fleet PR

Average Performance Ratio across all monitored sites in the portfolio for a given period.

Expected PR

The benchmark PR set in the asset metadata (often 75–85%). Used to flag sites underperforming relative to their design specification.

Loss Waterfall

A breakdown of energy losses from theoretical maximum down to actual output, categorised by cause: grid downtime, plant downtime, inverter underperformance, soiling, clipping, curtailment, and unclassified losses.

Soiling Loss

Energy lost because dust, dirt, or debris on the panel surface reduces the amount of sunlight reaching the cells.

Clipping Loss

Energy wasted when the inverter limits (clips) the output because the PV array is generating more power than the inverter can convert.

Curtailment

Intentional reduction of output, typically due to grid constraints or operator instruction.

BESS

Battery Energy Storage System — rechargeable battery installation that stores surplus solar energy for use when the sun is not shining.

SoC

State of Charge — the current charge level of a battery as a percentage of its total capacity (0% = empty, 100% = fully charged).

Charge Power

Rate at which energy is being stored into the battery (kW). Positive = charging.

Discharge Power

Rate at which energy is being drawn from the battery (kW). Positive = discharging.

SaaS

Solar as a Service — Daystar delivers solar energy as a managed service. The system typically consists of PV panels and optionally a battery; the client pays for energy, not equipment.

PaaS

Power as a Service — Daystar delivers reliable power from multiple sources (solar, grid, generator) as a single managed service. More complex than SaaS; involves hybrid energy management.

Genset

Generator set — a diesel or gas-powered backup generator used when solar and battery cannot meet load demand, common in PaaS deployments.

ATS

Automatic Transfer Switch — automatically switches the site between power sources (solar/battery ↔ generator ↔ grid) without manual intervention.

NOC

Network Operations Centre — the team that remotely monitors all sites, triages alerts, raises tickets, and coordinates field responses.

FSE

Field Service Engineer — the technician who physically travels to and works on sites to carry out repairs, preventive maintenance, and inspections.

SLA

Service Level Agreement — contractual time targets for responding to and resolving incidents. E.g. Critical = respond within 2 hours, resolve within 24 hours.

MTTR

Mean Time to Repair — the average time taken to restore a system to operation after a fault. A key maintenance efficiency metric.

OT Head

Operations & Technology Head — senior stakeholder responsible for technical operations at the client organisation.

GHoF

Group Head of Facilities — senior client stakeholder responsible for site facilities management.

PC Manager

Project Coordinator Manager — client-side project manager overseeing the Daystar engagement.

AMMP

Asset Monitoring & Management Platform — the external IoT monitoring platform used by Daystar. Provides live telemetry, performance KPIs, alerts, and historical energy data via REST API.

Telemetry

Automated real-time data transmitted from on-site devices (inverters, meters, sensors) to the AMMP platform via a local data logger.

Data Quality

A measure of how recently a site sent data to AMMP. Statuses: OK (<1h old), Warning (1–6h), Stale (6–24h), Offline (>24h). Sites that go "dark" are monitoring blind spots.

Asset ID

The unique UUID assigned to each site in the AMMP platform. Required to fetch any AMMP data for that site.

CO₂ Offset

Tonnes of CO₂ emissions avoided by generating solar energy instead of drawing from the fossil-fuel-based grid. Calculated as: PV generation (kWh) × grid emission factor (kgCO₂/kWh) ÷ 1000.

co2_offset_factor

Per-asset emission factor (tCO₂/kWh) configured in AMMP. If this is not set for a site, the Environmental Impact section will show no data.