Stiebel Eltron Accelera 300 E Heat Pump Water Heater Review

Key Summary

The Stiebel Eltron Accelera 300 E is a 79.8-gallon, German-engineered, true heat pump water heater designed to cut water heating costs by up to 80% compared with standard electric models. With a high 3.609 UEF efficiency rating, a 74.2-gallon first-hour rating, and a 10-year warranty, it targets homeowners who prioritize long-term energy savings and reliability over the lowest upfront price. Its strengths include efficiency and durability, while limitations include size, weight, upfront cost, and the need for suitable ambient temperatures between 42°F and 108°F.

TL;DR

• The Accelera 300 E is a true heat pump water heater (not a hybrid), using a dedicated compressor-based heat pump as the primary heat source with a 1500W electric booster for backup.
• It offers a 79.8-gallon tank, 3.609 UEF efficiency, a 74.2-gallon first-hour rating, 60 dB sound power level, and 324 CFM airflow, supporting medium to larger households with steady hot water demand.
• Real-world DOE estimates indicate roughly 1,289 kWh of yearly energy use and around $155 in annual operating cost, often translating to up to 80% lower water heating costs than standard electric tanks, depending on local rates and use.
• It runs on a 15-amp 240-volt circuit, uses R134a refrigerant, and is designed to operate in spaces where ambient air temperatures stay between about 42°F and 108°F.
• Strengths include high efficiency, long 10-year warranty, European track record (over 30 years in heat pump water heaters), and robust engineering; trade-offs include bulk, weight, noise, and limitations in colder or confined spaces.
• Best suited for homeowners with sufficient mechanical room space, moderate to warm ambient air, and a focus on long-term energy savings rather than the lowest upfront cost.

Product Introduction

If you are evaluating high-efficiency water heaters for a residential or light-commercial building, the Stiebel Eltron Accelera 300 E sits in a growing category of heat pump water heaters that aim to slash electricity use while still delivering reliable hot water. Before you scroll through a product carousel or compare options side by side, this review walks through how the Accelera 300 E is built, how it performs, and what its real-world pros and cons look like compared to conventional electric tanks and other heat pump models.

What is the Stiebel Eltron Accelera 300 E Heat Pump Water Heater?

The Stiebel Eltron Accelera 300 E is a high-efficiency, electric heat pump water heater with a nominal storage capacity of 79.8 gallons. It is designed primarily for residential and light-commercial applications where occupants want to reduce water heating energy use while maintaining a generous supply of hot water. Unlike many “hybrid” heat pump water heaters that frequently rely on large electric resistance elements, the Accelera 300 E functions as a true heat pump system, using a compressor and refrigerant loop as its main heat source and a relatively small 1500W electric booster for backup.

• Tank capacity: 79.8 gallons, suitable for medium to larger households or mixed-use light-commercial spaces.
• Uniform Energy Factor (UEF): 3.609, indicating more than three times the efficiency of a typical standard electric resistance water heater.
• First-hour rating: 74.2 gallons, meaning it can deliver roughly this amount of hot water in the first hour of heavy use when fully heated.
• Operating temperature range for ambient air: 42°F to 108°F, defining where the heat pump can operate as intended.
• Sound power level: 60 dB, with a sound pressure level around 52 dB at 3.3 feet, similar to a typical conversation or a quiet dishwasher.
• Airflow rate: 324 CFM, which is the volume of air the heat pump moves through its evaporator coil while extracting heat.

The Accelera 300 E is part of a product family that has been refined over several decades in Europe, where Stiebel Eltron has been a key player in heat pump water heater technology for more than 30 years. The 300 E model is tailored to North American electrical and test standards while carrying over the brand’s focus on efficiency and durable design.

True Heat Pump Design vs. Hybrid: How the Accelera 300 E Works

A central distinction of the Accelera 300 E is that it functions as a true heat pump water heater rather than a hybrid model that frequently defaults to electric resistance heating. In practice, this design choice shapes its efficiency, operating behavior, and cost savings potential.

In a heat pump water heater, a sealed refrigeration loop moves heat from surrounding air into the water tank. The Accelera 300 E uses R134a refrigerant and a compressor to capture low-grade heat from ambient air and upgrade it to a useful temperature for heating water. The main components involved are:

• Evaporator coil and fan: The unit draws room air across the evaporator coil, where the refrigerant absorbs heat and evaporates. The fan in the Accelera 300 E moves about 324 CFM of air during operation.
• Compressor: The compressor raises the pressure and temperature of the refrigerant, enabling it to deliver heat to the tank.
• Condenser: Instead of an internal coil, Stiebel Eltron uses a condenser that wraps around the outside of the tank, transferring heat through the tank wall to the stored water.
• Expansion device: After releasing its heat, the refrigerant passes through an expansion device, drops in pressure and temperature, and is ready to absorb heat again.

Because the heat pump is the primary heat source, the Accelera 300 E typically delivers more heat energy to the water than the electrical energy it consumes. This is reflected in the unit’s coefficient of performance (COP) and its UEF rating of 3.609. Rather than relying on large resistance elements to heat water directly, the system leverages ambient air as the main heat source, which generally leads to lower operating costs.

Role of the 1500W Booster Heater

The Accelera 300 E includes a 1500W electric booster heater. This element is relatively small compared with the 4500W or 5500W elements found in many conventional electric or hybrid water heaters. The booster is designed as a backup for conditions such as:

• Periods of unusually high hot water demand, where the heat pump alone may not recover the tank temperature quickly enough.
• Colder ambient air conditions near the lower end of the operating range, where heat pump performance temporarily declines.
• Anti-legionella or high-temperature cycles, where the unit raises water temperatures above typical setpoints.

Because the booster power is limited, the unit retains its identity as a true heat pump water heater. Most of the annual energy delivered to the water comes from the heat pump cycle, not from the booster resistance element, which is key to achieving lower energy use over time.

Efficiency, UEF, and Cost Savings: How the Accelera 300 E Cuts Bills by Up to 80%

The standout metric for the Accelera 300 E is its Uniform Energy Factor (UEF) of 3.609. UEF is a standardized way to compare water heaters based on how much usable hot water they deliver per unit of energy consumed over a test cycle. A typical new conventional electric water heater may have a UEF around 0.90 or slightly higher, while heat pump models range from roughly 2.0 to above 4.0.

With a UEF over 3.6, the Accelera 300 E can theoretically deliver more than three and a half times as much useful hot water output per unit of electricity compared with a basic electric tank. In practical terms, this means that a household that moves from an older or standard electric water heater to the Accelera 300 E can often see water heating energy reductions approaching 70–80%, depending on hot water use patterns and local electric rates.

DOE Yearly Energy Use and Operating Cost

The U.S. Department of Energy (DOE) test procedure estimates that the Accelera 300 E will use about 1,289 kWh of electricity per year with typical residential usage. At national average electricity rates, this corresponds to an estimated annual operating cost of around $155. For context, a standard 80-gallon electric water heater with a much lower UEF might use three to four times as much energy in the same test scenario, resulting in proportionally higher bills.

Actual savings will vary by household. You may see larger savings if:

• Your current water heater is older, undersized, or poorly insulated, causing higher standby losses.
• Your electricity prices are above the national average, making each kilowatt-hour more expensive.
• You maintain a steady hot water usage pattern that aligns well with the heat pump’s ability to recover between draws.

Conversely, savings may be less dramatic if your electrical rates are very low, if your existing heater is already relatively efficient, or if your ambient air conditions regularly fall below the optimal operating range and force the booster heater to run more often.

Where the “Up to 80% Savings” Comes From

The claim of up to 80% reduction in water heating costs is based on comparing the high UEF and corresponding DOE energy use of the Accelera 300 E with typical older or standard electric water heaters with UEF ratings around 0.9 or below. Because a heat pump water heater can deliver several units of heat for each unit of electrical energy consumed, the majority of the energy used to heat water is effectively drawn from ambient air rather than directly from the electric grid. In favorable conditions, this difference can dramatically lower your water heating electricity use and, therefore, your utility bills.

German Engineering and Stiebel Eltron’s Heat Pump Track Record

Stiebel Eltron is a German manufacturer that has specialized in electric water heating and renewable energy systems for many decades. In Europe, the company has produced and refined heat pump water heaters for over 30 years, where energy costs, building standards, and climate policies have long favored high-efficiency equipment. The Accelera 300 E reflects this background in several ways:

• Use of a wraparound condenser to reduce the risk of tank corrosion at internal coil penetrations and to support even heat transfer across the tank wall.
• Emphasis on efficiency metrics tested to European standards as well as U.S. DOE procedures, providing insight into performance across varied conditions.
• Integration of controls and safeguards tuned to keep the heat pump running as the primary heat source, rather than quickly defaulting to resistance elements.

For homeowners and light-commercial owners, the long history of heat pump technology in the European market may be relevant when comparing brands. A manufacturer with decades of experience in a specific technology may offer more mature designs and long-term field data than newer entrants, although real-world reliability still depends on proper sizing, installation quality, and maintenance.

Key Specifications: Capacity, Noise Level, Airflow, and Operating Range

Beyond efficiency metrics, the practical experience of living with a heat pump water heater depends on details like tank size, noise, airflow, and where the unit can operate effectively. For the Accelera 300 E, several specifications stand out.

79.8-Gallon Capacity and 74.2-Gallon First-Hour Rating

With a 79.8-gallon tank and a first-hour rating of 74.2 gallons, the Accelera 300 E is sized for households with moderate to high hot water demand. This might include families with multiple bathrooms, frequent showers, and simultaneous uses like laundry or dishwashing. The first-hour rating indicates how much hot water the heater can deliver in the first hour of use starting with a full tank, accounting for both tank capacity and the rate at which the heater can recover.

Because the Accelera is a true heat pump model, its recovery rate can be slower than a high-wattage resistance water heater. However, the large tank volume helps buffer this by providing a substantial reserve of hot water, especially when draws are spread out across the day rather than concentrated in a short time window.

Sound Power Level: 60 dB (Approx. 52 dB at 3.3 Feet)

Heat pump water heaters make noise because they use a compressor and fan. The Accelera 300 E has a sound power level of 60 dB and a measured sound pressure level around 52 dB at a distance of 3.3 feet (1 meter). This is in the range of a quiet conversation or a low-speed bathroom fan. In many mechanical rooms, basements, or utility areas, this noise level is unlikely to be disruptive, but it can be more noticeable if the unit is installed near living spaces or in acoustically reflective rooms.

When planning installation, it is worth considering door and wall construction, as well as any open returns or ducts that might transmit sound to bedrooms or living areas. In multifamily or light-commercial buildings, noise can also be a factor if mechanical rooms share walls with offices or other quiet spaces.

Airflow: 324 CFM and Its Impact on Your Space

The Accelera 300 E moves about 324 cubic feet per minute (CFM) of air across its evaporator coil. This airflow enables efficient heat transfer from the ambient air to the refrigerant but also means the unit has a noticeable effect on the room where it is installed. Specifically, it will:

• Cool and dehumidify the room air as it extracts heat, which can be a benefit in warm or humid climates (for example, in a basement in summer).
• Potentially overcool small, enclosed rooms in cooler climates if there is not enough makeup air or if the space is already near the lower end of the operating temperature range.

In some installations, ducting kits or louvered doors are used to ensure adequate airflow to and from the space and to direct the cooled exhaust air where it is most beneficial or least disruptive. When planning an installation, pay attention to room volume, other equipment in the space, and local climate.

Operating Temperature Range: 42°F to 108°F

The specified operating ambient temperature range for the heat pump system is approximately 42°F to 108°F. Within this range, the heat pump can efficiently extract heat from the air and deliver it to the water. If ambient temperatures fall below the lower limit, the compressor may not operate correctly, and the system may rely more heavily on the electric booster heater or shut down to protect itself.

For homeowners, this means the Accelera 300 E should be installed in spaces where temperatures stay within this range most of the time, such as conditioned basements, well-insulated mechanical rooms, or interior utility rooms. Placing the unit in unconditioned garages or sheds in cold climates can significantly reduce efficiency and reliability unless the space is designed to maintain adequate temperatures year-round.

Electrical Requirements and Refrigerant: What You Need to Know

The Accelera 300 E is designed for North American electrical systems and uses a common refrigerant type. Understanding these details helps ensure compatibility with your home’s infrastructure and informs long-term environmental considerations.

15-Amp 240-Volt Circuit and Power Draw

Electrically, the Accelera 300 E operates on a 220–240-volt, 60 Hz circuit with a recommended 15-amp breaker. The rated power consumption for the compressor and fan is about 650W, while the booster heater adds 1500W of capacity when it is engaged. Together, they can draw more power than the heat pump alone, but the overall demand remains significantly lower than many conventional electric water heaters that often have 4500W or larger elements.

Because the current draw is relatively modest, many homes can accommodate the Accelera 300 E without major electrical service upgrades, especially if an existing electric water heater circuit is already in place. Still, a qualified electrician should verify breaker sizing, wire gauge, and panel capacity to ensure code-compliant installation.

R134a Refrigerant: Performance and Environmental Context

The Accelera 300 E uses R134a refrigerant, a common choice in many heat pump and refrigeration applications. R134a is a hydrofluorocarbon (HFC) that offers good thermodynamic performance but has a relatively high global warming potential (GWP) compared with some newer refrigerants. In everyday operation, the refrigerant is contained within a sealed loop and does not enter the environment under normal conditions.

Environmental impacts primarily arise if refrigerant leaks occur during the unit’s lifetime or if proper recovery practices are not followed at end-of-life. When comparing options, some homeowners may prioritize models that use lower-GWP refrigerants, while others focus more on overall energy efficiency and operational carbon reduction, which the Accelera 300 E provides through reduced electricity use compared with standard electric water heaters.

Real-World Performance: How the Accelera 300 E Behaves in Homes

Laboratory ratings like UEF and DOE annual energy estimates are helpful, but homeowners often want to know how a unit feels and behaves day to day. While every installation is different, several patterns commonly show up when heat pump water heaters like the Accelera 300 E are installed in typical homes.

Hot Water Availability in Medium and Larger Households

In a three- to five-person household with common usage patterns—morning showers, evening dishwashing, and laundry—an 80-gallon heat pump water heater with a 74.2-gallon first-hour rating is generally adequate when the unit is properly set up. Users often find that spacing out hot water-intensive activities or slightly adjusting schedules helps ensure reliable supply without frequently triggering the booster element.

If multiple high-flow showers run concurrently and for long periods, or if large soaking tubs are filled regularly, a heat pump water heater’s slower recovery can be more noticeable than with a conventional high-wattage resistance heater. In such cases, users may need to raise the setpoint (within safe limits) or adjust usage habits, which can modestly reduce efficiency but still retain much of the energy savings compared with a standard tank.

Impact on Room Temperature and Humidity

Because the Accelera 300 E extracts heat from ambient air and expels cooled, dehumidified air, it often behaves like a small air-conditioner or dehumidifier in the space where it is located. In warm, humid basements, this side effect can be welcome, reducing mold risk and improving comfort. In cooler climates or smaller rooms, however, the cooling effect may be less desirable and can contribute to lower room temperatures, especially during extended operation.

To manage this, some installations provide a pathway for cooled air to be directed to spaces where cooling is beneficial, or they provide a source of makeup air from warmer areas of the building. Attention to ventilation and room size can help maintain the ambient temperature within the unit’s preferred range, preserving efficiency and reliability.

Noise and Everyday Living

At around 52 dB sound pressure at 3.3 feet, the Accelera 300 E is noticeable when running but comparable to many household appliances. Homeowners often describe the noise as a low hum or a soft fan sound. In a basement or closed mechanical room, this is usually unobtrusive. In a utility closet adjacent to living spaces or bedrooms, the noise may be more apparent, making door seals, insulation, and room placement worth considering during design.

Durability, Warranty, and Maintenance

Beyond efficiency, long-term value depends on how long the unit lasts and what protection the manufacturer offers. For many homeowners, the length and terms of the warranty offer a practical proxy for expected durability and manufacturer confidence.

10-Year Warranty and Build Quality

The Accelera 300 E carries a 10-year warranty on the tank and heat pump components when installed and operated according to the manufacturer’s instructions. A decade of coverage is competitive within the heat pump water heater category and indicates that Stiebel Eltron expects the tank and compressor system to provide long service life under typical residential conditions.

The design uses a heavy, well-insulated tank and external wraparound condenser, which can reduce the number of penetrations into the tank wall and may lower the risk of certain types of leaks. However, as with any water heater, long-term reliability still depends on water quality, sediment control, and periodic maintenance tasks like inspecting the anode rod where applicable, flushing sediment, and verifying condensate drainage.

Maintenance Requirements

Typical maintenance tasks for a heat pump water heater such as the Accelera 300 E include:

• Cleaning or inspecting air filters to maintain proper airflow and efficiency.
• Ensuring the condensate drain and spillover systems are clear and functioning to prevent water damage.
• Flushing the tank periodically to reduce sediment buildup, especially in areas with hard water.
• Having a qualified technician check refrigerant lines and electrical connections if any performance issues arise.

These tasks are generally similar to or slightly more involved than those for conventional water heaters but can be managed as part of regular home maintenance schedules. Maintaining airflow and condensate drainage is particularly important in heat pump units, as blockages can reduce efficiency or cause nuisance shutdowns.

Installation Considerations: Space, Location, and Climate

A successful installation often matters as much as the product choice itself. The Accelera 300 E has specific space, climate, and handling considerations that homeowners and contractors should understand before committing to this model.

Size, Weight, and Handling

Physically, the Accelera 300 E is a large and heavy unit. It stands roughly 75 inches tall and has a diameter around 27 inches. The dry weight is close to 298 pounds, and when filled with water it can weigh about 957 pounds. This significant weight requires careful planning for transport, placement, and floor loading capability, especially on elevated structures or in older homes with wooden joist framing.

Moving the unit into tight basements or mechanical rooms may require additional labor and equipment such as dollies, straps, or even partial disassembly of doors or stair railings. These factors can increase installation complexity and cost compared with a smaller, lighter water heater.

Room Volume and Ventilation Needs

Since the Accelera 300 E draws and exhausts room air, it works best in spaces with adequate volume and airflow. Small, sealed rooms can experience rapid cooling and may drop below the recommended ambient temperature range, especially in colder climates. In such cases, installers may need to provide louvered doors, wall grilles, or ducting solutions to bring in warmer air and exhaust cooled air, keeping the system within its operating envelope.

In contrast, open basements or mechanical rooms in mild or warm climates often provide an ideal environment. The heat pump can operate efficiently, and the cooling and dehumidification of the air can even be seen as a secondary benefit.

Climate Suitability

The Accelera 300 E can be used in a wide range of U.S. climates, but performance and savings will vary. In warmer regions where ambient air within the installation space tends to stay well within the 42°F to 108°F range, the unit can operate with high efficiency for most of the year. In colder regions, careful placement in semi-conditioned or fully conditioned space becomes more critical to avoid frequent reliance on the booster heater.

For households in very cold climates, it may be necessary to consider how the heat pump’s cooling effect interacts with the home’s heating system. In some scenarios, the home’s space heating system may need to work slightly harder to offset the heat extracted by the water heater, which can modestly reduce net whole-house energy savings. Even so, many installations still see significant water heating energy reductions compared with conventional electric tanks.

Comparing the Accelera 300 E to Standard Electric and Other Heat Pump Water Heaters

When deciding whether the Accelera 300 E is the right choice, it helps to compare it against both standard electric water heaters and other heat pump models in terms of efficiency, performance, cost, and practicality.

Versus Standard Electric Water Heaters

Compared with a conventional electric storage water heater, the Accelera 300 E offers significantly higher efficiency and lower operating costs, as indicated by its UEF of 3.609 and DOE annual energy use of 1,289 kWh. The trade-offs include a higher upfront cost, more complex installation logistics due to size and weight, and potential impacts on room temperature and humidity.

For homeowners who plan to stay in their home for many years, the long-term savings on energy bills can often offset the higher initial cost, especially where electricity rates are moderate to high. In rental or short-ownership situations, or where electric rates are unusually low, the payback period may be longer, and basic electric heaters may remain more common despite their lower efficiency.

Versus Other Heat Pump Water Heaters

Compared with other heat pump water heaters, the Accelera 300 E sits in the upper range of tank size and efficiency. Some hybrid models from other brands may have slightly faster recovery rates due to larger resistance elements or multiple operating modes but may default to resistance heating more often, reducing real-world efficiency. In contrast, the Accelera 300 E’s smaller 1500W booster and control strategy aim to keep the heat pump in primary control as much as possible, preserving efficiency.

Other differentiators include the use of R134a versus newer refrigerants, specific noise profiles, and brand-specific warranties. Some competing models may offer integrated smart controls, demand-response capabilities, or app-based monitoring, which can be appealing to certain users. Homeowners comparing options should weigh efficiency, control features, refrigerant type, warranty, and total installed cost, rather than focusing on a single metric.

Strengths of the Stiebel Eltron Accelera 300 E

The Accelera 300 E offers a set of clear strengths that make it a strong candidate for many energy-conscious homeowners and light-commercial property owners.

• High efficiency and low operating cost: With a UEF of 3.609 and DOE estimated yearly use of 1,289 kWh, it targets substantial energy and cost reductions compared with standard electric tanks.
• True heat pump design: The system relies on the heat pump as the main heat source, with a modest 1500W booster element, helping maintain consistent efficiency rather than frequently defaulting to resistance heat.
• Large capacity and strong first-hour rating: A 79.8-gallon tank and 74.2-gallon first-hour rating support the needs of medium to larger households or light-commercial applications.
• Established European heat pump heritage: Stiebel Eltron’s more than 30 years of experience with heat pump water heaters in Europe underpins the design and engineering approach of the Accelera line.
• 10-year warranty: Long warranty coverage suggests confidence in the durability of both tank and heat pump components, assuming proper installation and maintenance.
• Beneficial side effects in certain climates: The unit’s dehumidification and cooling effect can help improve comfort in warm or humid basements and mechanical rooms.

Potential Limitations and Situations Where It May Not Be Ideal

Despite its strengths, the Accelera 300 E is not the best fit for every household or building. Understanding its limitations helps set realistic expectations and informs better product selection.

• Higher upfront cost: The initial purchase and installation price is typically higher than that of standard electric water heaters, and sometimes higher than smaller or lower-efficiency heat pump models.
• Size and weight: Its physical bulk and nearly 300-pound dry weight can make delivery and installation more challenging, especially in tight spaces or older homes.
• Dependence on ambient temperature: Efficiency and performance rely on maintaining room temperatures in the 42°F to 108°F range. Very cold or small enclosed spaces may force more booster operation or require additional ventilation measures.
• Cooling effect may be undesirable in some climates: While beneficial in hot, humid conditions, the cooling and dehumidifying effect can increase space heating needs or reduce comfort in colder regions if not carefully managed.
• Noise considerations: At around 52 dB at 3.3 feet, the unit is relatively quiet for a mechanical system but may still be audible if installed near bedrooms or living areas without sound isolation.
• Use of R134a refrigerant: Some users may prefer equipment using lower-GWP refrigerants, especially in regions with stricter refrigerant regulations or specific sustainability goals.

Is the Stiebel Eltron Accelera 300 E Right for Your Home or Light-Commercial Project?

Whether the Accelera 300 E is an appropriate choice depends on your hot water demand, installation conditions, and financial priorities. It tends to be a strong fit in scenarios such as:

• Medium to large households that regularly use significant hot water but want to control long-term operating costs.
• Homes with basements or mechanical rooms that stay within the recommended temperature range and have sufficient volume for airflow.
• Light-commercial applications like small offices, multi-unit residential common areas, or small hospitality settings with moderate hot water usage.
• Projects where long-term energy savings and carbon reduction are higher priorities than the lowest possible upfront cost.

On the other hand, it may be less suitable for very small households with low hot water demand, homes in extremely cold climates with only unconditioned spaces available for installation, or situations where space and structural limitations make moving and supporting a large, heavy water heater impractical.

How to Decide Between the Accelera 300 E and Other Options

If you are comparing the Accelera 300 E to alternative models, a structured decision process can help clarify your priorities. Consider the following steps when evaluating options:

• Define your hot water needs: Estimate daily and peak hot water usage based on the number of occupants, bathrooms, and typical routines, then compare this to tank sizes and first-hour ratings.
• Assess your installation space: Measure access paths, mechanical room size, ceiling height, and floor capacity, and consider temperature conditions throughout the year.
• Review local energy costs and incentives: Compare expected operating costs and available rebates or tax credits for high-efficiency water heaters, which can improve payback periods.
• Consider long-term plans: If you plan to own the property for many years, higher-efficiency units may provide better lifecycle value even if the upfront cost is higher.
• Consult a qualified installer: Have a licensed plumber or HVAC contractor review your space and electrical system to confirm feasibility and estimate installed costs for different options.

Using this framework, many homeowners find that the Accelera 300 E aligns well with long-term energy and comfort goals, provided their space and climate conditions are compatible with a large, true heat pump water heater.

Sources

• Stiebel Eltron — Accelera 220 E / 300 E technical specifications (PDF) https://www.stiebel-eltron-usa.com/sites/default/files/pdf/tech-specs-accelera-e.pdf
• U.S. Department of Energy — Water heater efficiency metrics and test methods (Energy Saver) https://www.energy.gov/energysaver
• ENERGY STAR — Heat pump water heaters product criteria and consumer guidance https://www.energystar.gov
• U.S. Environmental Protection Agency — Overview of refrigerants and global warming potential (EPA) https://www.epa.gov
• Stiebel Eltron — Company history and heat pump product overview https://www.stiebel-eltron-usa.com