The United States should reduce the energy it uses to heat water by 25% by 2020, mainly through the use of solar and advanced water heaters. That is the conclusion of a report, 'A Technology Roadmap' developed by the industry and funded by the Department of Energy’s Solar Energy Technologies Program.
The country consumes 100 billion kWh of electricity each year to heat water in homes and apartments, 1 trillion cubic feet of natural gas, 900 million gallons of oi and 500 million gallons of LPG. “This energy comes at a significant cost,” the report notes. The average home spends US$207 per year to heat water, the third-largest household energy expense behind space heating and space cooling. Electric and gas water heaters dominate the residential market, accounting for 99% of units sold and 93% of the energy consumed by water heaters.
The use of solar water heaters, geothermal heat pump water heaters, tankless electric, high-efficiency natural gas, and gas-fired tankless systems account for a very small share of the national market, and these technologies offer significant energy (and water) savings and reduced GHG emissions that “will not be realized unless they are developed and brought to market in a sustained and orderly manner.”
The goal of the roadmap is to reduce primary fossil fuel use for water heating by 25% by 2020, and accomplishing that goal will require “integrated and focused technology and market transformation activities.” It will also require development of “efficient, user-friendly products that can compete in the market on the basis of price, performance, and value-added attributes such as environmental protection, insurance against supply interruptions, and the ability to meet multiple residential/commercial needs.”
Solar Water heaters can reduce energy consumption by 50 to 75% and whole house electric tankless by more than 20% (when compared to a conventional water heater), and high efficiency natural gas water heaters can be more than 20% more efficient than conventional gas water heaters. On a national scale, installation of high efficiency natural gas water heaters in residences alone could save 223 billion cubic feet of natural gas (about=24 days worth of imports from Canada). Eliminating 50% of the electricity consumed to heat water by installing solar water heaters could save almost 55 billion kilowatt-hours per year (about 26 days worth of electricity from the nation's nuclear power plants).
According to the Roadmap Solar water heating has several barriers to use:
- Cost - Solar water heater cost about $2600, up to ten times more expensive than conventional water heaters. Development of polymer, rather than glass and metal, collection systems is targeted to cut that cost in half. The economies of high volume production would further reduce the cost. Long term financing, by utilities or the government, could reduce the cost to acceptable levels. The Lakeland Electric utility has a program where they install and maintain the water heater for free and they charge the customer for the amount of hot water used, at a cost less than would be incurred by an electric water heater. The utility reduces its peak demand and transmission losses. The program generates a 7% annual rate of return for the utility and it generates Renewable Energy Credits for the utility. Incentives and tax credits are widely used and encurage implemetation in the states where they are available.
- Reliability - Although early models were not very reliable, these problems have been eliminated in modern systems installed in temperate climates. Freeze-up problems in more severe climates can be solved by using an active (pumped with temperature sensors) system rather that the drain-back systems used in temperate climates. Water heaters used in Germany, which has a climate similar to that in the norther snow belt in the U.S., have overcome this problem. An equivalent (based on population) 150,000 solar water heating systems are installed annually in Germany, which highly subsidizes the installation, vs. 6,000 in the U.S.
- Education - A plumber or plumbing supply house that is educated about the types of solar water heaters and benefits are more likely recommended installation of a solar heater than those that are not educated. Manufacturers and distributors need a more active education program that is disseminated to consumers, builders, plumbing unions, industry associations and retailers.
- Training and licensing - Solar water heaters are more complex than conventional water heaters, installing them may require knowledge or experience that is not normally part of the training for plumbers that are the key sales route for water heaters. The North American Board of Certified Energy Practitioners is in the process of drafting a certification/licensing program for solar water heaters which will be released for comment by the solar community. Certification/licensing should go a long way towards ensuring that installers are well informed of the design and safety issues involved with with solar water heaters as well as the proper installation and operating procedures.
- Building practices and codes - Preparing a home, during construction, for solar water heating is a relatively easy cost effective avenue for energy and resource conservation. A minimum requirement should be that rough-ins, from the water heater to the attic, suitable for running piping and electrical wires should be required when the home is being constructed. Installing dry piping and conduit should be required if they could not easily be installed during a retrofit. Requirements that houses be oriented so as to best take advantage of solar incidence is a more controversial possibility. Making code officials, developers and builders aware of the desirability of these requirements should be part of the educational program.
Electric Water Heaters
Advanced, high-efficiency water heaters (heat pumps,tankless instantaneous, and geothermal) are generally more expensive to purchase that conventional water heaters. Their advantage over solar water heaters is that the technology is usually more mature. Generally similar measures, as were outlined for solar water heaters, for cost, education, training practices and building practices need to be implemented. The details of each of these points are different than for solar water heaters and are explained in the main Roadmap document.
Roadmap developed to expedite solar water heating in U.S., reFocus website, Elsevier, November 30, 2005
Solar and Efficient Water Heating, A Technological Roadmap, 2005 (pdf, 73 pages), Represenatives of the Water Heater Industry and DOE, 2005