Accelera: True Heat Pump Water Heaters


Accelera 300 Heat Pump Water Heater

These are not a 'hybrids.' They're heat pump water heaters.

Decades of heat pump experience made it obvious to us that a heat pump water heater ought to make hot water with the heat pump, and not with a back-up element. This simple solution seems to have escaped others. Yet it has made our heat pump water heater the largest seller in Europe for 30 years.


“Hybrid” Water Heaters Mode Accelera® Heat Pump Water Heaters
Their most efficient mode provides the greatest savings they’re capable of. Water heater operates only with the heat pump.

“Hybrids” must be set to the correct mode in order to either save energy or provide comfort.
Heat Pump This is our only “setting.” Accelera® is engineered to satisfy 90% of hot water needs through the use of the heat pump alone. In cases of high demand, one specially-designed electric “booster” element is located at the very top of the tank. Positioned near the hot water draw point, the element has been designed and engineered to run as little as possible so that comfort is maintained and savings maximized.
Two standard electric elements activate for fast water temperature recovery. System allows heat pump to work once demand has been met via electric elements. Hybrid Accelera® is designed to satisfy hot water needs without having to pick a setting. There is nothing to remember to choose in order to have both comfort and savings.
Two standard electric elements activate sooner and stay on longer than in their “hybrid” mode. High Demand Accelera® is engineered to work as a harmonious whole. Both comfort and savings are achieved without having to ask, “what setting do I need to choose today?”
Heat pump is disabled and only their two electric elements heat the water. “Hybrids” don’t have active defrost and must enable this mode so the evaporator can defrost. This mode is also selected if the heat pump fails. Standard We engineered the Accelera® so the heat pump doesn’t need to be disabled for a defrost cycle. We also engineered for reliability. Why pay extra for a heat pump water heater if you’re just going to end up with a standard electric tank?
Water heater maintains a very low temperature in the tank then reheats the water the day before you return. Vacation Mode Our super-insulated tank keeps water hot in an Accelera® during a 2-week vacation for less than $4. No one has to worry if vacation mode was set to wake up on the correct day.

Energy from nature

Extract energy from the air.
Accelera® can extract up to 80% of its energy requirements from the energy in the air around it.
Heat pump water heating technology means the amount of energy needed to create hot water is greatly reduced compared to any water heater. This ground breaking technology redefines the efficiency a water heater is capable of. For every watt the Accelera’s compressor and fan uses, the equivalent of 3-5 watts of hot water are generated. The best so-called “high efficiency” water heaters can only approach making the equivalent of 1 watt of hot water for every watt of energy they consume.

Designed to use the backup element as little as possible

Accelera® heat pump water heaters have been designed to supply 80% of an average annual household's hot water with energy supplied by the heat pump, not by the backup element. This leads to the lowest possible energy costs for hot water and still supplies sufficient hot water to keep everyone happy. One way we do this is to prevent the cold water entering the tank during a draw from mixing with the hot water already in the tank. That way the maximum amount possible of hot can be drawn before the backup element is needed.

Specially designed single element for backup

Specially designed single element for backup

If the heat pump cannot keep up with the demand for hot water then the specially engineered electric backup element supplies additional heat to the water. The single back-up element is located at the very top of the tank. This design ensures comfort during periods of high demand, in addition to high efficiency. In a warm climate, an Accelera® is placed either in the garage, where it takes heat from the outside air, or inside the house, where it helps with the air conditioning load. In a cooler climate, the unit is typically placed in the basement where it also acts as a dehumidifier. You get hot water at a discount plus a drier basement as well.

How a heat pump works in an Accelera®

An Accelera® works like an air conditioner, but instead of transferring the heat outdoors, it transfers it into the tank of water. This process is many times more efficient than any other water heater. It works like this:

The fan moves room air through the evaporator, which contains liquid refrigerant that extracts heat from the ambient air as it evaporates. As the refrigerant warms, it changes into a gas.

The warm gaseous refrigerant passes through the compressor which increases its pressure. As the pressure increases, the temperature of the refrigerant rises until it becomes hot.

The hot refrigerant then passes through the condenser wrapped around the water tank. Because heat travels from hot to cold, the heat in the refrigerant transfers to the water in the tank.

The refrigerant, now a super-cool liquid, passes through the expansion valve to become a warmer, yet still cold, liquid, ready to become a gas again in the evaporator and continue the cycle.

The Accelera® uses environmentally-friendly R134a for its refrigerant.

State and Local Rebates & Incentives

Regional incentives for the Accelera® are available in many locations. The U.S. Department of Energy’s Database of State Incentives for Renewables & Efficiency website has up-to-date details at:


ETL Certified for US & Canada Energy Star High Efficiency Water Quality Association Gold Seal Lead Free Logo
Tested and certified by
Water Quality Association against
NSF/ANSI 372 for lead free compliance.
ISO 9001 Certified
Ten-year limited warranty