NEW YORK — David Kincaid of Shreveport, La., wanted to save energy, but he needed a little nudge. When he learned of a free online program that would reward him, he was sold.

The 31-year-old husband and father of four tackled his home efficiency upgrades with a simple mission in mind: "Low budget, high returns."

His first step was taking a few minutes to sign up on Earthaid.net. It's one of many new online tools to help people reduce their energy consumption and, in some cases, reward curbed emissions with any number of prizes: a back massage, a yoga mat or cold hard cash — your choice.

Two programmable thermostats, two water heater blankets and 25 fluorescent light bulbs later, Kincaid reaped $300 in utility savings and, as a reward, three new oak trees for his front yard. The upgrades cost him about $260 and it took only a few months to rake in the savings and the greenery.

This is a nascent market, but experts say before long anyone with a utility bill will be debating the virtues of services such as Earth Aid, Google PowerMeter and My Emissions Exchange as casually as they compare smartphones.

That's because these services address two pressing issues that touch everyone: the weight of your wallet and the health of the environment.

Each year the average household spends about $2,200 on utilities and spews 22,300 pounds in carbon dioxide emissions. With just a few basic energy upgrades, consumers could pocket an average of $660, or 30 percent of their spending, and shrink their carbon footprint by as much as 8,000 pounds each year, according to the Environmental Protection Agency.

If these online tools gain mass appeal they could play a key role in curbing U.S. residential emissions, which make up nearly 13 percent of the nation's total, according to the Department of Energy.

For David Kincaid, Earth Aid helped his family understand their energy consumption with detailed graphs that tracked their natural gas, electric and water usage. The program automatically pulls and analyzes the data, mapping out spending and emissions patterns and year-over-year comparisons. Its social networking function lets users compete with friends and neighbors in saving energy.

"It makes it easier for us as parents to explain (energy) to our kids and for them to see a tangible result of their actions," Kincaid said. Now the kids are quick to switch off lights and shut down electronics, with the hope that they can soon plant another oak tree.

Meanwhile, Tami and Randy Wilson are receiving their rewards in cash through My Emissions Exchange, www.myeex.com, a carbon broker that combines residential and small business carbon savings and sells them as credits to companies that want to offset their emissions. MyEex takes a 20 percent cut of the sale.

On MyEex, anyone with a utility bill can enter their monthly data on the Web site, send copies of their bills to MyEex for verification and get paid for every ton of carbon reduction achieved.

When their utility announced a steep rate increase, the Wilsons installed solar panels on their 1,500-square-foot home, cutting their monthly electric bill from $100 to $0.

Between the monthly utility savings, hefty government subsidies, solar renewable energy certificates and a few carbon credits, the Wilsons expect to pay off their $58,000 solar system in six years.

The Google PowerMeter application takes a slightly different approach to motivate consumers. It pulls data from energy monitoring devices to chart a household's real-time energy consumption.

PowerMeter is compatible with store-bought devices such as The Energy Detective and AlertMe. The real-time data let consumers see times of the day when energy use is high and identify appliances and habits that draw the most power.

This is one area where it pays to be an early adopter, said Mick Womersley, associate professor and director of sustainability at Unity College in Maine. The products are free and can bring savings right away.

"It's a 100-dollar bill on the ground that consumers should pick up."