Heat pump EER

Heat pumps move heat from one place to another. Some can pump heat both out of and into a building, for cooling or heating. Air conditioners (or "chillers" for large-scale systems) are a kind of heat pump that can only pump heat out of a building, but can do it slightly more efficiently than bi-directional heat pumps.

Small-scale heat pumps.

Heat pumps are important for efficient HVAC systems because moving heat can use less energy than generating heat. Heat generators can never be more than 100% efficient because the energy they use is directly creating heat, but heat pumps effectively can because they just move heat from one place to another. However, based on the operating environment, sometimes boilers are more effective. This is the case particularly in cold outdoor temperatures (below 5°C or 40°F).

To think about moving heat rather than generating it, imagine a tanker truck driving fuel from one place to another-the truck may be hauling thousands of liters of fuel as cargo, but truck's own gas tank only holds a few dozen gallons, because that's all the fuel it needs to burn to carry the load to its destination. In the same way, heat pump move heat energy as cargo, using a bit of electric energy to do so.

Heat pumps can move several units of heat energy per unit of electricity

Measuring Efficiency

There are many ways to measure the effectiveness of a heat pump:

is the simplest measurement. It measures the amount of heat energy moved (in watts), divided by the electric energy used to move it (also in watts), at a given outdoor temperature. Higher COP values indicate a more efficient system. An electric resistance heater generating heat at 100% efficiency will have COP = 1, while a heat pump in heating mode ranges from a COP of 2 to 5, and a heat pump in cooling mode ranges from 3 to 12.

is similar to COP, but for only for cooling. It measures how efficiently a cooling system operates. EER is most commonly applied to window units and smaller standalone air conditioners and heat pumps. The EER is the ratio of Btu/hr of cooling divided by the watts of electricity used at an outside temperature of 95°F (35°C). Room air conditioners should have an EER of at least 9.0 for mild climates and over 10.0 for hot climates.

measures how efficiently a smaller residential air conditioner or heat pump operates over an entire cooling season, as opposed to a single outdoor temperature. As with EER, a higher SEER reflects a more efficient cooling system. SEER is the ratio of the total amount of cooling Btu's the system provides over the entire season divided by the total number of watt-hours it consumes.

measures how efficiently heat pumps operate in heating mode over an entire heating season. It is like SEER but for heating. The higher the HSPF, the more efficient the system. HSPF is calculated by dividing the total number of Btu's of heat delivered over the heating season by the total number of watt-hours of electricity required to deliver that heat.

kW/ton measures the energy input in kW over the tons of cooling provided. Unlike other metrics, the lower the ratio, the more efficient the chiller. This metric is most often used to determine efficiency of large-scale chillers.