The Low Down On Green Living
February 11th, 2009
We’ve always found it a bit strange that one of the most energy-intensive systems in our homes wasn’t covered by the Energy Star program: water heaters. Water heaters are particularly challenging to select. They’re expensive, they employ several different technologies, and unlike many appliances you can’t just judge their merits based on what you see in a store.
Well, Energy Star has finally stepped up and given us some guidance. The standards for hot water heaters were released last year, and as of January 1 many different manufacturers now offer Energy Star models. So what does an Energy Star water heater mean for you? As you might expect, it differs by category, so we’ll run through them and list some good options for you below.
Storage Hot Water Heaters
Storage hot water heaters are the ones most of us have in our homes - a big tank with a burner at the bottom. They’re the least efficient type of hot water heater, for significant energy is lost as the hot water sits in the tank regardless of the insulation level. The new Energy Star standards say that a storage hot water heater must have an Energy Factor of at least 0.62, meaning that 62% of the energy in the fuel burned is converted into heat in hot water. This is about 7% more efficient than the current minimum federal standard for storage hot water heaters. If you’re on a budget, then these models are best.
Some options include:
Tankless Whole-House Hot Water Heaters
The new Energy Star standard for tankless hot water heaters is that they must have an Energy Factor of 0.82. This isn’t that stringent: most quality tankless units already meet or exceed this level. However, the Energy Star certification also specifies that the warranty be at least ten years on the heat exchanger and five years on parts. This is a major upgrade for some manufacturers. Tankless hot water heaters make sense if you don’t have huge hot water demands and if space is at a premium in your home.
Gas Condensing Water Heaters
Gas condensing water heaters are very similar to the traditional storage hot water heaters from the outside. But inside, there’s a major difference: they have very efficient heat exchangers that capture much more of the heat from burning fuel than do traditional models. An Energy Star condensing model must achieve an Energy Factor of at least 0.8, which puts most of these models right up there with tankless versions. That efficient heat exchanger comes at a price, though, so they’ll be more expensive than your typical storage model. Condensing models are great if you have a large family with high hot water demands - the storage gives you a bit more capacity than a comparable tankless unit.
Heat Pump Water Heaters
The previous three hot water heaters all employ gas as a fuel. So what happens if you use electricity? Consider a heat pump hot water heater. Like a normal heat pump or air conditioner, a heat pump water heater uses a refrigerant to “move” heat from outdoors inside to heat your water. Because you’re moving rather than creating heat, the efficiencies are incredibly high: Energy Star heat pump water heaters have Energy Factors of > 2.0. Per unit of energy, though, electricity is often much more expensive than gas or propane, so this higher efficiency might not translate into higher savings.
Solar Hot Water Heaters
Solar hot water heaters convert the sun’s energy into hot water, so why isn’t every solar hot water an Energy Star? The answer is that if they’re too small then they won’t make much of a difference. Therefore, an Energy Star solar hot water heater must have a Solar Fraction of > 0.5, meaning that it provides at least 50% of your total hot water heating needs.
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