David Kluth makes a statement nearly every day with his work wardrobe.

It's not a fashion statement, per se, but Kluth's green T-shirt and baseball camp symbolize what he does for a living.

Kluth usually wears a green T-shirt and baseball cap to work, which makes sense because he is the owner of Renewable Energy Center, a Menomonee Falls store that specializes in environmentally-friendly products like cordless electric lawn mowers, synthetic motor oil that needs changing every 25,000 miles and solar powered water heating systems, battery chargers and attic fans.

He also sells biodiesel systems that allow you to use waste oil to heat your house or run your car or boat.

"With the economy the way it is, everybody is looking to save a little money," Kluth said recently at his store, located at N90 W16937 Appleton Ave.

"There are a lot of ways you can do that. Sometimes, it's the little things that can really add up."

As an example, Kluth points to the Neuton battery-powered lawn mower, which he allows customers to test by cutting grass in the cemetery behind his shop.

"Think of what you're spending to put gas in your car," he said. "You're spending a lot for the lawn mower, too. This mower costs about $470 bucks, which is on the high end for a push mower, but it runs for about 10 cents an hour.

"If you keep it for five years, it can pay for itself."

Kluth, who has operated his store since 2005, began selling Solatube skylights and solar-powered attic fans before branching into other products.

"Every year, I try to add a couple new things," he said. "I started out with the skylights and the attic fan.

"The attic fan can save you two or three hours on your air conditioning and it can prevent ice dams that happen in the attic.

"As I started talking to people and researching things, I found more products to sell like insulated concrete forms that you see in a lot of new construction. That's basically a cement wall with 2 ½ inches of Styrofoam on both sides. They put the rebar in there. It's 60 to 70 percent more efficient than a normal wall.

"If you have a heating bill that is $300 a month, you can knock that down to $100."

Kluth spends a lot of time doing that kind of math for his customers interested in "green" building and saving green. "I talk to a lot of people who are building new houses," he said. "If you're going to build a house for $400,000, why spend $50,000 on countertops? In 10 or 15 years, those are going to be old-school.

"Why not put in decent countertops and spend $40,000 on solar and things that can save you money over the long haul? A solar electrical panel lasts 100 years. If you have a 100-watt panel, it will produce about 95% efficiency."

Kluth's enthusiasm increases as he continues a tour of his showroom. The FuelMeister, which retails for about $2,700, converts waste oil to diesel fuel for autos, trucks and anything else that usually takes gas.

"It's like home brewing," Kluth said. "I can make a gallon of biodiesel for about 65 cents. I run my house on it. I've got a burning furnace right next to my natural gas furnace."

Kluth gets waste oil from a couple local restaurants, but worries that it may become more scarce.

"A couple years ago, they'd pay you to take it away," he said. "Then it was free. Now, some places try to charge for it."

One of Kluth's biggest sellers these days is a solar system for heating pools. "If you put in a solar system to heat the water in your house, it can take six or seven years for it to pay for itself," he said. "But, a solar pool system costs $2,000 or $3,000 and it can pay for itself in one year.

"A lot of rich people that have in-ground pools are spending from $3,000 to $6,000 to heat their pools at 82 degrees or above. A lot of them are sick of paying that. Why not spend the money up front? Now, you can open the pool two or three weeks beforehand and keep it open two or three weeks longer than you did before."

As oil prices and environmental awareness increase, Kluth figures to see his business increase as well.

"I used to install satellite TV systems," he said. "The money was OK. I was doing pretty well. But, I like this a lot more because I feel like I'm doing something positive."