With energy-consuming equipment, such as water heaters and refrigerators, we have good data on energy consumption and can set clear standards accordingly. In some product categories—clothes washers, for example—Energy Star standards were adopted because those standards provide a high enough threshold to represent just the very top segment of the product market (less than 10%). In other product categories—e.g., refrigerators and dishwashers—we set a higher threshold than ENERGY STAR: for example, exceeding those standards by 10% or 20%. With lighting and lighting control equipment, certain generic products qualify, such as compact fluorescent lamps and occupancy/daylighting controls, while in other categories only a subset of products qualify. In some cases, products that meet the energy efficiency requirements are excluded, because of evidence of poor performance or durability. Microturbines are included here because of the potential for cogeneration (combined heat and power) that they offer.
The Armstrong FloDirect™ Direct Fired Water Heater (formerly the DFT Hot Water Generator) for commercial and industrial applications can produce up to 600 gpm with a 145°F temperature rise (peak temperature 185°F). Its efficiency nears 100% because of the recovery of heat lost in combustion exhaust. It is suitable for hospitals, hotels, laundries, industrial plants and other facilities where large volumes of hot water are needed.
The most efficient fuel-fired water heaters include electronic-ignition gas-fired tankless (on-demand) models, direct-contact commercial water heaters, and advanced combination space- and water-heating systems.
Gas-fired condensing storage-tank type water heaters have fuel efficiencies greater than 90% and use a variety of types of insulation. Tankless water heaters have no standby losses, and some models have sealed combustion and no pilot lights. In combined or integrated systems, efficiencies are boosted by uniting space heating and/or cooling into a single system that includes water heating.
Other factors to consider include indoor air quality (in terms of combustion gases), particularly whether the system has sealed combustion with direct venting to the outdoors and/or enhanced combustion emissions controls (for NOx, particulates, etc.), and whether it is capable of continued operation in the event of a power outage. In almost every type of high-efficiency water heater there are issues of rate-of-use, climate, and maintenance that require consideration to make the appropriate selection for optimal results.
Commercial-sized water heaters listed here have thermal efficiency ratings of at least 96% for gas and 87% for oil, or have a high thermal efficiency along with additional environmental features such as sealed combustion. To date, neither CEE nor Energy Star has a commercial water heater standard.
Ratings and Commentary