- Self-sufficiency (SSR)
- Self-Sufficiency Ratio — the share of household consumption covered by your own solar. 100% would mean zero grid dependency.
- Self-consumption (SCR)
- Self-Consumption Ratio — the share of GENERATED energy used directly on-site rather than exported to the grid.
- Round-trip efficiency (RTE)
- Round-Trip Efficiency — the percentage of energy put into a battery that comes back out. The rest is charge/discharge loss (typically 85–95%).
- State of charge (SOC)
- State of Charge — the battery's current charge level as a percentage of capacity, right now.
- State of health (SOH)
- State of Health — battery wear compared to new (100%). Declines with cycles and age; relevant to warranty.
- MPPT
- Maximum Power Point Tracking — the inverter circuit that continuously finds the panel operating point with the highest output.
- Specific yield
- Annual output per 1 kWp of installed capacity (kWh/kWp/year) — lets you compare installations of different sizes.
- Performance ratio (PR)
- The ratio of actual output to theoretically expected output under given conditions (weather/tilt/azimuth) — the main indicator of whether a system performs as it should.
- kWp
- Kilowatt-peak — the nominal (peak) power of a solar system under standard test conditions, not instantaneous output.
- Export ratio
- The share of generated energy exported to the grid (sold at a feed-in price, usually far lower than the purchase price).
- Grid dependency
- The share of consumption covered by grid purchases — the complement of self-sufficiency (SSR) up to 100%.
- PVGIS
- Photovoltaic Geographical Information System (JRC, European Commission) — a free tool giving expected solar output for a given location/tilt/azimuth. Used as the comparison baseline.
- Tilt and azimuth
- Tilt = the panel angle from horizontal (0° flat, 90° vertical). Azimuth = the compass direction the panel faces (in this app, 0° = south, negative = east, positive = west).
- Battery cycles
- The number of complete battery charge/discharge cycles — the main driver of wear (SOH) alongside age.