Data Points Series
Combined heat and power (CHP) systems, also known as cogeneration, generate electricity and useful thermal energy in a single, integrated system. Heat that is normally wasted in conventional power generation is recovered as useful energy, which avoids the losses that would otherwise occur from separate generation of heat and power. While the conventional method of producing usable heat and power separately has a typical combined efficiency of 45 percent, CHP systems can operate at efficiencies of 60–80 percent or more.
Building codes have protected people with minimum health and safety requirements for buildings since the Code of Hammurabi in 1754 BCE. Energy provisions in US codes have protected owners and tenants from excessive energy waste since the 1970s. They set minimum performance levels for energy features in new buildings and renovations, notably insulation, windows, air sealing, and to some extent, lighting and heating and cooling equipment.
Heavy-duty vehicles (more than 8,500 lbs. gross vehicle weight) are central to our economy: tractor-trailers carry goods, vocational trucks and heavy pickups help provide services, and transit buses transport passengers. In 2015, heavy-duty vehicles represented only 5% of on-road vehicles but consumed 30% of all highway fuel. Tractor trucks dominate this sector, accounting for about two-thirds of heavy-duty oil consumption, followed by vocational vehicles and heavy pickups.
Utilities have options when it comes to meeting customer demand for electricity. They can build power plants to convert fossil fuels to energy. They can capture renewable resources like solar and wind. And they can work with residents and businesses to lower demand by implementing energy efficiency programs.
Electric utilities and independent statewide program administrators deliver a substantial share of efficiency programs across the country. Some utilities have delivered such programs for decades. Since the mid-2000s, though, the size and scope of the programs have grown dramatically. Today, utilities and administrators implement energy efficiency programs in all 50 states and the District of Columbia.
Appliance efficiency has increased remarkably over the past several decades. The graph below tracks the energy efficiency of four household appliances over a 35-year period. Three of the products (clothes washers, central air conditioners, and refrigerators), show a 50% or greater reduction in energy use over that period, and the fourth product, gas furnaces, shows a smaller but still significant reduction of 18%.
Over the past 40 years, light-duty vehicles in the United States have achieved remarkable gains in both fuel economy and performance. The graph below shows average miles per gallon, power-to-weight ratio, and 0-to-60 acceleration time of new cars and light trucks since the late 1970s. Fuel economy improved dramatically from 1975 to 1987, driven by the original Corporate Average Fuel Economy (CAFE) standards, which were adopted in 1975 in response to the 1973 oil embargo by Arab states.
The industrial sector, which includes dozens of individual industries spanning agriculture, forestry, fisheries, construction, mining, and manufacturing, accounts for about one-fifth of the US gross domestic product. Industry is unique among the end-use sectors in that its energy intensity has declined consistently over the past 35 years, as can be seen in the figure below.
Energy efficiency comes into a house from many directions: standards make appliances, equipment, and electronics more efficient, building codes ensure the right amount of insulation and ventilation, utility programs help families manage their energy use, and smart technology saves money with programmable thermostats and energy-sipping LED lighting. So it may come as a surprise that, according to the Energy Information Administration (EIA), on-site residential energy consumption actually grew 8.9% from 1980 to 2009.
From 1980 to 2014, energy use in the United States increased from 78 quads (quadrillion Btus) to 98 quads, an increase of 26%. (A quadrillion is 10 to the 15th power.) But over the same period, our gross domestic product (GDP) increased by 149%. A common approach for looking at these two variables together is to examine energy intensity, defined as energy use per real dollar of GDP.