I'll update this message with links.
http://home.businesswire.com/portal/site/google/index.jsp?ndmViewId=news_view&newsId=20051012005756&newsLang=en"Natural gas water heaters are less expensive than electric models to operate, and they heat water up to twice as fast: Homeowners can cut water heating costs by 50 percent by using natural gas," Sitherwood said.
http://www.consumerreports.org/main/detailv4.jspConsider gas. Based on national average fuel costs, gas heaters cost roughly half as much to run as electric models and can pay for their higher up-front cost in as little as a year. Factor in the cost of running a gas line to your home if you don’t have one. Also consider adding insulation to hot-water pipes and the cold water pipe exiting the water heater.
http://www.eere.energy.gov/femp/technologies/eep_electric_waterheaters.cfmWhere natural gas is available on-site, a gas water heater will almost always be more cost-effective than an electric model. Depending on the climate and energy costs, a solar-assisted or heat pump water heater may result in substantial energy and cost savings.
http://www.google.com/search?q=cache:CLA-c2MgGZwJ:www.efficiencyvermont.com/Docs/Heating%2520Switch%2520Release_FINAL.doc+vermont+energy+heat+gas&hl=en&ie=UTF-8Joint Announcement from: Efficiency Vermont, Burlington Electric Department, Central Vermont Public Service and Green Mountain Power.
Considering a Switch to Electric Heat? – Think Again