For Michelle Vogt, it's as if her hot water heater leaked dollar bills.

The 40-year-old Woodland resident said her monthly energy tab soars to as much as $1,200 every summer, and she believes that her 7-year-old water tank is one of the main causes.

"It's heating all day," said Vogt, who noted that her neighbor's monthly bills are about $300 less. "It's got to be that."

An in-home energy audit confirmed Vogt's hunch.

For three hours Tuesday, technicians with San Mateo solar provider SolarCity scoured Vogt's four-bedroom home, looking for signs of energy-guzzling appliances, inadequate insulation and air leakages that that add to cooling costs in the summer and heating bills in the winter.

Using high-tech equipment such as infrared cameras to track warm and cold air flows, and an air pressure gauge known as a manometer, SolarCity's experts concluded that simple upgrades such as a new water heater could cut Vogt's energy bills by about 15 percent, or up to $180 a month.

More expensive retrofits, such as the installation of rooftop solar panels, could save even more.

The recommended fixes – not including the solar system – would cost about $6,000 after the available rebates.

The savings would pay for the cost of the upgrades in about five years, said Scott Lowery, energy efficiency training leader for SolarCity.

Vogt said that she and her husband, Casey Vogt, will probably make most of the recommended changes, and sock away the savings to help pay for their young children to eventually attend college.

"Gosh, we were thinking about how much we could do with that money," said Vogt, who helps manage her family's rice farm in Yuba City. "Our (energy) bills are pretty much like a mortgage payment."

Vogt is one of scores of PG&E or Sacramento Municipal Utility District customers who have received an in-house audit since the program was launched last year. An audit is required before utility customers can qualify for sizeable energy retrofit rebates, funded in part by federal stimulus dollars.

Energy contractors such as SolarCity perform the audits on behalf of the utility.

Because they're Pacific Gas and Electric Co. customers, the Vogts paid $299 for their audit. SMUD customers pay just $99 because the utility is using federal stimulus money to subsidize the cost.

PG&E offers rebates of up to $4,000 for major retrofits based on savings projected by these audits. SMUD, meanwhile, provides rebates of up to $9,000 on major upgrades.

Lowery said energy audits typically find savings of up to 30 percent, especially on older homes. Since the Vogts' home was built just nine years ago, it's much more energy-efficient than older models.

The owners, he added, have good insulation in their attic and have installed tinting on their windows to keep out heat.

Still, SolarCity's audit found areas for improvement.

The water heater is an obvious example. Hot water tanks built today are 15 percent to 20 percent more energy-efficient and better insulated than Vogt's 7-year-old model.

Replacing the existing tank would save about $30 a month, Lowery said.

Unplugging all those vampires – devices that suck power even when they're not turned on – and doing away with an electric space heater also would help cut the Vogts' bills.

It costs the same amount of money to run a 1,500-watt portable heater for two or three hours as it does to run a gas furnace for 24 hours, said Lowery.

Household electronics such as television sets, DVD players or personal computers can use up to 80 percent as much electricity on standby power as they do when they are turned on.

According to Lowery, improvements to the home's air ducts and other air passages would generate the biggest savings for the Vogts.

During their inspection, SolarCity's technicians found that parts of the house leaked as much as a quarter of their air. The air leakage makes it more expensive to cool the home in summer and to heat it in winter.

Areas around plumbing fixtures, lights and overhead fans contribute to the loss of air. Windows and doors typically leak about 15 percent of the air in a home, but air passages next to a home's fixtures and plumbing are responsible for much greater leakage – as much as 45 percent.

According to Lowery, air leakage costs the Vogts as much as $100 a month.

A sealant applied to the surface of the air ducts and other surfaces will not only remedy the problem of energy loss but will also improve the air quality in the Vogts' home by keeping out moisture that can contribute to mold, Lowery said.

"Fixing a leaky air duct is … one of the low-hanging fruits," he said. "It's not very glamorous or sexy, but it gives you the best bang for your buck."

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