| \(\eta\) | Nutzungsgrad, Effizienz, Ausnutzung | Performance ratio, efficiency, utilisation factor | — |
| \(\beta\) | Belastungsgrad | Load level, load factor | — |
| Q˙ | Wärmeleistung | Heating power | W, kW |
| 𝑉˙ | Volumenstrom | flow rate | m3/h |
| 𝑞˙ | spezifische Wärmeleistung | specific heating power | W/m2 |
| \(\theta\)‾ | Mittlere Temperatur | mean temperature | °C |
| A | Fläche | area | m2 |
| a | Anteil | fraction | — |
| b | Überdimensionierungsfaktor der Pumpe | Pump overdimensioning factor | — |
| c | Koeffizient | coefficient | — |
| C | Konstante | constant | — |
| c | spezifische Wärmekapazität | specific heat capacity | kJ/(kg·K) |
| COP | Leistungskennzahl | coefficient of performance | — |
| d | Zeit, Zeitspanne, Tage | Time, time period, days | d, d/a, d/mth |
| e | Aufwandszahl | expenditure factor | — |
| E | monatliche solare Bestrahlungsenergie | Monthly solar radiation energy | kWh/(m2·mth) |
| EEI | Energieeffizienzindex | Energy efficiency index | — |
| F | Faktor | factor | — |
| FBH | Fußbodenheizung | underfloor heating | — |
| g | Gesamtenergiedurchlassgrad bei senkrechtem Strahlungseinfall | total energy transmittance for perpendicular incidence of solar radiation | — |
| H | Wärmetransferkoeffizient, allgemein | heat transfer coefficient, general | W/K |
| h | Höhe | height | m |
| HK | Heizkörper | radiator | — |
| L | Länge | length | m |
| n | Luftwechselrate | air change rate | h-1 |
| P | Leistung | Performance, power | W, kW |
| p | Druck | pressure | kPa |
| Q | Energie | energy | kWh |
| q | spezifische Energie | specific energy | Wh/(m2·d), kWh/(m2·a) |
| t | Zeit, Zeitspanne | Time, time period, hours | h, h/d, h/mth, h/a |
| U | Wärmedurchgangskoeffizient | thermal transmittance | W/(m2·K) |
| V | Volumen | volume | m3 |
| W | Hilfsenergie | auxiliary energy | kWh |
| \(z\) | Tägliche Laufzeit der Zirkulationspumpe | Daily running time of the circulation pump | h/d |
| \(\alpha\) | Anteil | fraction | — |
| \(\gamma\) | Wärmequellen-/Wärmesenken-Verhältnis | heat-balance ratio, ratio of heat sources to heat sinks | — |
| \(\Delta\) | Differenz | difference | — |
| \(\theta\) | Temperatur | temperature | °C |
| \(\kappa\) | Deckungsanteil | Cover ratio | % |
| \(\sigma\) | Stromkennzahl | CHP code | — |
| \(\Phi\) | Wärmestrom | energy flow rate, power, heat flow | W |
| \(w\) | Wichtungsfaktor | weighting factor | — |
| \(\rho\) | Dichte | density | kg/m3 |
| \(\tau\) | Zeitkonstante (einer Gebäudezone) | (thermal) time constant (of a building zone) | h |
| \(\vartheta\) | Temperatur | temperature | °C |
