SPF (Seasonal Performance Factor) is a measure of the annual energy efficiency of heat pumps and air conditioners. This indicator gives a more accurate picture of the system's performance, as it takes into account the total heat energy produced throughout the year and the energy consumption of the system, including any additional electric heating.
How is SPF calculated?
The SPF value is calculated using the following formula:
SPF = Total thermal energy produced ( kWh ) / Total energy consumption (kWh)
Total heat energy produced (kWh): The total heating or cooling energy produced by the heat pump during the year.
Total energy consumption (kWh): The total electrical energy consumption of the system during the year, including:
- The energy consumption of the heat pump.
- The energy consumption of any additional electric heating.
- The consumption of other electrical components (e.g. pumps, fans) necessary for the operation of the system.
Difference between SPF and COP
COP (Coefficient of Performance): Measures the performance of a heat pump at a given moment, under laboratory conditions. It does not take into account seasonal changes or periodic loads.
SPF (Seasonal Performance Factor): Reflects the annual energy efficiency, taking into account the effects of real-world conditions such as weather, temperature fluctuations and additional heating. Therefore, SPF is a more accurate indicator for assessing the actual efficiency of the system.
SPF value example calculation
A heat pump produces 10,000 kWh of heating energy over the year, while its total energy consumption (including electric additional heating) is 2,500 kWh:
SPF = 10,000 kWh / 2,500 kWh = 4
This means that the system produced 4 kWh of thermal energy over the year using 1 kWh of energy.
How can SPF be influenced?
Outdoor temperature: In colder weather, the efficiency of the heat pump decreases, which can result in a lower SPF value.
Seasonal fluctuations: SPF takes into account the operation of the heat pump throughout the year, so seasonal temperature changes have a significant impact on the indicator.
Heat pump type: Air-to-water heat pumps typically have a lower SPF than ground-to-water systems, which operate from a more stable temperature source.
Additional heating: The use of electric additional heating reduces the SPF value as it increases the energy consumption of the system.
Optimal installation: Proper sizing and installation ensures that the system operates at the best possible efficiency.
Regular maintenance: Periodic cleaning and servicing of the system helps maintain original performance.
SPF values and categories
SPF values are often categorized to make it easier to understand the effectiveness of the systems:
| SPF value | Evaluation | Features |
|---|---|---|
| SPF < 2.5 | Low efficiency | Less modern or poorly sized systems. |
| 2.5 ≤ SPF < 3.5 | Medium efficiency | Older systems or unfavorable operating conditions. |
| SPF ≥ 3.5 | High efficiency | Modern, well-sized systems in ideal conditions. |
Summary
SPF (Seasonal Performance Factor) is one of the most important indicators for evaluating the annual energy efficiency of heat pumps and air conditioners. It gives a more accurate picture of the system's performance than a single COP measurement, as it takes into account factors that vary throughout the year. Systems with a high SPF value are more efficient, economical and environmentally friendly, so considering SPF is key when choosing the right system.