Name – Default component text and counters are automatically added. This entry may be edited to include other descriptive or identifying text.

Water Heater Type - Select from one of three choices:

• Storage Tank - Conventional -  A conventional setup where a heater heats water in a storage tank, keeping it at a set temperature until needed. When hot water is used, the tank refills and reheats. Older tanks are sometimes retrofit with insulation blankets to reduce stand-by losses, or the energy wasted when a water heater maintains stored hot water at a set temperature, even when no hot water is being used. Can be heated by either electricity of fossil fuels.
• Storage Tank - Heat Pump - Uses electricity to transfer heat from the air into the water, making it much more energy-efficient than conventional electric storage tanks. If kept in conditioned space, these heat pump water heaters will pull heat from conditioned space to heat the water. This mechanism cools the conditioned space as a consequence and benefits buildings in hotter climates.
• Instantaneous - Also called demand-type or tankless water heaters, these heat water on demand as it flows through the unit, eliminating the need for a storage tank. By eliminating storage tanks, instantaneous water heaters eliminate stand-by losses. These are often used in applications with limited space and lower hot water use. Can be heated by either electricity or fossil fuels.

Fuel Type – The type of fuel used to heat water. Pull-down menu selections:  Electricity or Gas.

Efficiency Units - Select the heating efficiency value that corresponds to your water heater:

• EF (Energy Factor) - The ratio of useful hot water energy output to the total energy consumed over a test cycle. This typically applies to all water heater types.
• UEF (Uniform Energy Factor) - Similar to EF but based on an updated DOE test procedure, which accounts for different household usage patterns. This applies to all water heater types.
• Et (Thermal Efficiency) - The percentage of energy input that is directly transferred into hot water under steady-state conditions (i.e., no cycling or standby losses). This typically applies to gas-fired water heaters, especially larger central systems.
• COP (Coefficient of Performance) - The ratio of heat energy output to electricity input in heat pump water heaters. Only applies to Storage Tank - Heat Pump.

Efficiency – Energy efficiency value for the given Efficiency Units. For instance, if your water heater efficiency is 0.63 EF, the efficiency would be 0.63 and your Efficiency Units should be set to EF.

Water Distribution Type – Select from two options:

• In-unit - Each zone in the thermal space has a dedicated service hot water heater. These units tend to have lower capacity and storage values. In a multifamily context, this would imply each residential unit (e.g., apartment, dwelling, condo) would have a dedicated hot water system.
• Central - A single large water heating system provides hot water to multiple units in a building. Typically high-capacity boilers, commercial storage tanks, or heat pump water heaters serve these scenarios. Selecting this option opens up the additional modeling parameters for piping specifications and recirculation.

Recirculation Loop - Only applies to Central water distribution types. A recirculation loop is a piping system that continuously circulates hot water throughout a building to reduce wait times and minimize water waste. It is commonly used in hotels, apartments, hospitals, and large homes where hot water demand is high and distribution pipes are long. This simulation engine models recirculation loops with a swing tank configuration, or a hybrid approach to hot water storage and heating, where variable demand is managed through a second, dedicated storage tank serves the recirculation loop. It is commonly used in commercial and institutional buildings with fluctuating hot water loads.

Water Heater Location - Select from two options:

• Conditioned space- the water heater, storage tanks, and distribution pipes are located within the insulated and temperature-controlled parts of a building (e.g., utility rooms, mechanical rooms inside apartments, or hallways in commercial buildings). Stand-by losses dump heat and heat pump water heaters pull heat from these spaces, affecting the building's thermal load.
• Unconditioned space- This means the water heater, storage tanks, and/or pipes are located in areas without temperature control, such as garages, attics, basements, crawl spaces, or outdoor mechanical rooms.

Insulation Blanket – Only applicable to storage tank configurations -- An insulation blanket is a thermal insulating wrap designed to reduce heat loss from a storage water heater. It helps improve energy efficiency by maintaining water temperature longer, reducing standby losses. These are often applied only to older, conventional storage tanks.

Piping - Percentage in Unconditioned Space – The percentage of piping that occurs in unconditioned space. Pipes in unconditioned space lose heat when sitting idle and require users to incur dump losses.

Piping - Percentage Insulated – The percentage of piping that is covered with insulation. 
Note: This model prioritizes insulating pipes in unconditioned spaces first. For example, if 80% of the building’s pipes are in unconditioned space and 40% of all pipes are insulated, then insulation will first be applied to unconditioned pipes. In this case, half of the unconditioned pipes (40% ÷ 80%) will be insulated before any conditioned-space pipes are considered.

Piping - Piping Insulation Thickness – The thickness of insulation applied to hot water piping. Three options are available:

•  Greater than 3/8 inch (> 3/8") – Provides the highest level of insulation, reducing heat loss and improving energy efficiency. 
• 3/8 inch (3/8") – A moderate level of insulation, offering some heat retention benefits. 
• Less than 3/8 inch (< 3/8") – The lowest insulation level, offering minimal heat loss reduction. 

Note: Thicker insulation is more effective at maintaining water temperature, reducing standby heat loss, and improving overall system efficiency, especially for pipes in unconditioned spaces.

Low Flow Faucets – Select if low-flow fixtures such as showerheads with flow restrictors, high-efficiency low-flow faucet and aerators, and auto-flush and ultra-low-flow toilets are installed and in use. The Asset Score simulation engine does not apply water and energy savings from low flow fixtures for the dump-loss portion of service hot water use in multifamily contexts.