Accelera 300 Heat Pump Water Heater: Save Energy Like Never Before !


Accelera 300 Heat Pump Water Heater

This is not a 'hybrid.' It's a heat pump water heater.

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.


“Hybrids” Mode Stiebel Eltron Accelera® 300
Their most efficient mode provides the greatest savings they’re capable of. Water heater operates only with the heat pump. Heat Pump This is our only “setting.” Accelera® 300 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® 300 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® 300 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® 300 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® 300 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. Our next generation of heat pump water heaters will have a vacation mode, because, after all, $4 buys a latte, but why worry if you don’t want to?

Energy from nature

Extract energy from the air.
The Accelera® 300 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

The Accelera® 300’s 80 gallon tank is designed to deliver 50 gallons of hot water before the backup heating element needs to activate. This means most household draws can be satisfied through the heat pump alone. This is one way we made the Accelera® 300 as efficient as possible. A full tank of 140°F water, for instance, is enough for 5 people to take 10-minute showers each, the equivalent of 126 gallons of 107°F water, before the back-up element is needed.

Specially designed single element for backup

If the heat pump cannot keep up with the demand for hot water then the specially engineered 1700 W 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® 300 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® 300

The Accelera® 300 works just like an air conditioner, but instead of dumping the heat outdoors like an air conditioner, it transfers it into the tank of water.

The heat pump system contains a fan that forces room air through an evaporator (1). The evaporator contains a 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 (2) which increases its pressure. As the pressure increases, the temperature of the refrigerant rises until the refrigerant becomes hot.

The hot refrigerant then passes through the condenser (3), which is wrapped around the water tank. Because heat travels from hot to cold, the refrigerant transfers its heat to the water.

The refrigerant, which is now super-cool liquid, then passes through an expansion valve (4), where it becomes a gas again and the process begins anew.

The Accelera® 300 uses environmentally-friendly R134a for its refrigerant.

State and Local Rebates & Incentives

Regional incentives for the Accelera® 300 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
The Accelera® 300 is tested and certified by
Water Quality Association against
NSF/ANSI 372 for lead free compliance.
ISO 9001 Certified
Ten-year limited warranty