There are many ways in which houses can conserve energy.
Improvements in energy-efficient lighting can reduce power usage by as much as 65 percent. In fact, if every American household changed just five of the most-used lighting fixtures to energy-efficient technology, they would save a total of $6 billion in costs and reduce power usage by the equivalent of the annual output of more than 21 power plants.
Many homes have high-performance, energy-efficient windows -- featuring double glazing or special coatings -- to reduce heat loss in cooler climates and heat gain in warmer climates.
These two factors account for 50 percent of a home's heating and cooling needs. Replacing window frames with low-conductance materials like wood, vinyl and fiberglass can also improve a home's insulating capability.
In the future, more homes will most likely incorporate solar cells, also known as photovoltaics. Solar cells are made of semiconductor materials (usually silicon), which absorb sunlight's energy and stores it until it is needed to power something. Unfortunately, solar cells can only absorb between 15-25 percent of sunlight's energy. This is because it only absorbs visible light; other kinds of light pass right through the cell as if it were transparent.
The prototype Solar House in Raleigh, North Carolina, only gets about half its total electricity needs from its photovoltaic system. Solar cells are also more costly than conventional electricity. Quite a bit of hardware is needed for energy capture, storage and conversion, for example, and these can be expensive.
While most households pay a fixed rate for their electricity -- that is, it costs them the same regardless of what time they are using it -- some utilities in Michigan are experimenting with an option called a time-of-use rate. This means that power used during peak usage hours costs more than off-peak consumption. To take advantage of this new trend, Whirlpool is developing new appliances that can be programmed to operate during off-peak hours to save homeowners money. Prototype washers, dryers, and dishwashers are currently being tested.