Recent energy efficiency regulations mean using cutting edge technologies for many new and replacement latest in water heaters. Although not explicitly required, only condensing gas heaters and heat pump electric heaters can meet the specified performance for tank sizes above 55 gallons. These technologies cost significantly more, but that’s balanced out by energy cost savings over the lifetime of the unit. So even if your tank size is smaller, these alternatives are well worth considering. Especially if your choice qualifies for a utility rebate or tax credit.
Hot water heaters are something most people don’t think about, even when a replacement is necessary. But give these “new” options some thought before you just go with whatever you happen to already have as a replacement. Condensing, heat pump, and tankless water heaters seem like something new in the US, but they’ve been the most common choices in Europe and Japan for many, many years.
Condensing Gas Models
With designs from not that long ago, a third of the burner’s energy went straight out the flue. But with the latest models as much as 97% goes into water.
Condensing units look and operate like the old standards, except for one big difference. There’s a special stainless steel heat exchanger that condenses water vapor out of the exhaust gases, recovering heat. They also typically use closed combustion for cleaner and more efficient burning. So rather than the usual efficiency of around 80%, models with these technologies go well above 90%.
With an exhaust hardly above room temperature they’re less expensive to vent. They also have much better first-hour recoveries, so you’re less likely to run out of hot water and may even be able to choose a less expensive unit with a smaller tank.
Electric Heat-Pump Models
Per unit of energy, electricity is much more expensive than natural gas. But sometimes there’s no good choice other than an electric hot water heater. Conventional models are already in the 90% efficiency range, but it’s actually possible to do better than “100%!”
Heat pumps don’t directly use electrical energy to heat water. Instead they “pump” thermal energy from their surroundings into the water. So for every kWh (kilowatt hour) of electricity used they move 2, even 3 kWh equivalent of heat. That’s a huge win in lowering your electric bill when compared to conventional electric models. But it does mean they shouldn’t be installed in heated areas. And they work best in warm climates. In fact, they don’t work at all below freezing temperatures. But no worries — most are technically hybrids, with a standard electric resistance element for those cold times.
Latest in Water Heaters – Tankless
Efficiencies approaching 100% are indeed impressive, but that ignores heat lost from the big water tank. Even with excellent insulation that brings gas heaters in the 80% efficiency range down to 60-70% (an EF — effective energy factor — of .6 to .7). Tankless water heater bring that back up to 80%+ by getting rid of that tank. Condensing tankless water heaters reach well into the 90% range.
How do they do it? With bigger burners and advanced heat exchangers (or bigger electric heating elements) they heat water as you use it. And you have an endless supply of hot water. Products from leaders such as AO Smith also feature ultra low NOX emissions and expected lifetimes on the order of 20 years.
Ultra-compact tankless models can often be located at the “point of use” in a kitchen or bath. They’re great for additions or adding capacity. And there’s no waiting — you get hot water out the tap almost instantly.
Rebates? Tax Credits?
To check out exactly what’s available in your particular location and what models qualify, visit www.dsireusa.org.