The difference between a fixed output and an inverter heat pump lies in how they deliver the energy needed from the heat pump to meet the heating demands of a property.
A fixed output heat pump works by continuously either being turned on or off. When turned on, the fixed output heat pump works at 100% capacity to meet the heating demand of the property. It will continue to do this until the heat demand is met and will then cycle between on and off heating a large buffer in a balancing act to maintain the requested temperature.
An inverter heat pump, however, uses a variable speed compressor which modulates its output increasing or decreasing its speed to match exactly the heat demand requirements of the building as the outdoor air temperature changes.
When the demand is low the heat pump will reduce its output, limiting the electricity usage and the exertion placed on the heat pump’s components, limiting the start cycles.
Inverter driven units offer far greater efficiency.
When compared to conventional fossil fuel-burning heating systems, both fixed output and inverter heat pumps offer far greater levels of energy efficiency.
A well designed heat pump system will provide a coefficient of performance (CoP) between 3 and 5 (depends whether ASHP or GSHP). For every 1kW of electrical energy used to power the heat pump it will return 3-5kW of heat energy. Whereas a natural gas furnace will provide an average efficiency of around 90 – 95%. Heat pumps will provide approximately 300%+ greater efficiency than burning fossil fuels for heat.
To get the maximum efficiency from a heat pump, homeowners are advised to leave the heat pump running continuously in the background. Leaving the heat pump switched on will keep a steady continuous temperature in the property, reducing the ‘peak’ heating demand and this most suits inverter units.
Less wear and tear with an inverter unit.
An inverter unit utilizes Brushless DC compressors which have no real start spike during a start cycle. The heat pump starts with a zero amp starting current and continues to build until it reaches the capacity needed to meet the demands of the building. This places both the heat pump unit and the electrical supply under less stress whilst being easier and smoother to control than an on/off unit. It’s often the case that where multiple start/stop units are connected onto the grid, this can cause issues and the grid provider may decline a connection without network upgrades.