Key Figures and Formulas: The Reference Guide
Technical metrics and formulas form the language of energy technology. This reference guide explains all the essential parameters for solar systems and heat pumps.
Solar System Metrics
kW, kWh, kWp, efficiency, C-rate – what do these figures mean and how do they assist with planning?
Read: Solar System Key Figures: The Glossary →Heat Pump Metrics
COP, SPF, bivalence point – the essential metrics for planning and evaluation.
Read: Heat Pump Key Figures and Sizing →Quick Reference: Essential Units
Photovoltaics
| Unit | Name | Meaning |
|---|---|---|
| kW | Kilowatt | Power (energy per unit time) |
| kWh | Kilowatt-hour | Energy (1 kW sustained for 1 hour) |
| kWp | Kilowatt-Peak | Maximum PV output under STC |
| % (η) | Efficiency | Useful output / input energy |
Battery Storage
| Unit | Name | Meaning |
|---|---|---|
| C | C-rate | Charge/discharge power relative to capacity |
| % DoD | Depth of Discharge | Maximum permissible discharge |
| Cycles | Lifetime | Charge/discharge cycles until 80% capacity |
Heat Pumps
| Metric | Name | Meaning |
|---|---|---|
| COP | Coefficient of Performance | Instantaneous efficiency ratio |
| SPF | Seasonal Performance Factor | Year-round efficiency |
| SCOP | Seasonal COP | Standardised annual efficiency |