I noticed you don’t mention water heaters. Since water heaters are an important household item, an explanation as to efficiency, energy uses, and global warming is warranted. Even with no testing there is a lot of general information out there that can help consumers make a better choice. I recently did my own research and called the Oregon State Department of Energy to get information. First, note that although water heaters rust out suddenly, the units are grounded to the water pipe so that there is a little time to make a good decision before you purchase a new model. Do switch off the circuit to the unit though.
The boring water heater is an important element in energy independence and global warming as well as energy bills. Up to 30% of an energy bill is consumed by heating water. In general, the choice of a water heater that makes the most cost sense also makes the most energy sense. So energy efficiency is an important guide. Note: Many of the past energy rebates are no longer available.
ELECTRIC VERSUS NATURAL GAS: There is not a simple choice between a natural gas unit and an electric unit. A gas unit will save substantially in monthly payments over an electric unit but the initial cost for a 0.60 gas unit is $200 more. In general, the gas unit is a better choice if you already have a gas furnace as the switch-over costs aren’t that large. Note that a 40-gallon natural-gas water heater can put out 69 gallons per hour–more than the 58 gallons per first hour that a 52 electric water heater can.
ENERGY SUPPLIES AND GLOBAL WARMING: But with a natural gas water heater the question arises, will our energy supplies hold out and will natural gas help or hinder efforts for global warming? Natural gas is still being discovered in the U.S. but it just is not keeping up with our increasing demand for its use. All energy prices are going up with time so a [decision] shouldn’t be based on the immediate fear of running out of natural gas.
As far as global warming is concerned, natural gas is cleaner burning than the coal or oil that is partially burned to produce electricity So in the short run (10 years or the expected life of a water heater) natural gas is better for global warming. But in the long run an electric water heater with reusable electric energy sources, such as wind, hydroelectric, or solar is better for the environment. In particular, natural gas should theoretically be saved for making pharmaceuticals or fertilizers and other such higher priority uses than generating electricity, which, in turn, is used to heat water. The national natural resources decision on our ultimate use of natural gas versus coal or electricity is still probably 10 years off.
HIGH-TECH WATER HEATERS: There are some quite high-tech water heaters for above $1,000 on the market. These will increase efficiency a little but may not pay for themselves before the warranty expires. Instantaneous gas heaters are also available for higher prices.
RECOMMENDATIONS: For most people an energy-efficient water heater is the least expensive way to help with energy independence, the environment and energy bills. The decision between natural gas or an electric water heater isn’t clear-cut as the availability of gas pipelines is not universal. In general, an electric water heater of 0.93 FTE efficiency is reasonably priced and fairly efficient. For about $50 more a switch comes with the unit which allows a homeowner to turn off the unit when the owner is away thus saving even more energy. Likewise, a natural gas water heater with a rating of 0.60 also meets the energy efficiency and economy considerations. Generally, natural gas water heaters start at $200 above an electric unit but pay for themselves over the 10- to 12-year life span.