Charlie and Susan Wing are about to invest $6,000 in a project that is expected to return $21,000 in ''interest'' over the next 10 years - and a whole lot more than that in the decades that follow.
Moreover, they are so enthusiastic about the project that they are taking steps to show others how to benefit in a similarly substantial manner.
The Wings recently bought a solid, turn-of-the-century farmhouse here, and they are investing the money in simple energy-saving improvements that computer analysis says will save them $21,000 in their total energy costs (heating oil, electricity for hot-water appliances, and so forth) over the next 10 years.
That's the equivalent of ''an interest rate unmatched by money-market funds, certificates of deposit, or anything else,'' Mr. Wing says.
In fact, the Brunswick couple will be spending an estimated $22,500 on home improvements. But the bulk of that money is for structural and cosmetic alterations; only $6,000 is for direct energy-saving changes.
''When the job is done, I want the house to look as new as the condominiums down the street,'' Mr. Wing says.
The return on the energy-saving portion of the investment comes to something like 35 percent; but even if the Wings calculate the entire cost of the alterations as an energy-saving investment, the return is still 9.3 percent. That compares well with other possible tax-free investments.
An energy audit shows that the Wings' 1,750-square-foot house currently requires 1,600 gallons of fuel oil a year to keep it at 68 degrees F. during the day and 55 degrees at night. After the improvements, 400 gallons will do the same thing. This means that the $6,000 spent on energy saving will be recouped in less than four years, and the entire cost in 11 years.
You would have to try hard to find a better investment today, in either cool or hot regions of the world, than energy conservation through caulking, weatherstripping, insulating, improving hot-water systems, and adding other passive-solar features to your home. The Wings stress this point over and over.
Actually, a family living in the average, poorly insulated American home can make money by borrowing from the bank to effectively insulate it, Mr. Wing insists.
''The payback in saved energy will be greater than the bank charges in interest,'' he says.
Mr. Wing, who for the past decade has been heavily involved in energy-saving retrofits, is not the least bit surprised by the predicted savings on the home. Most laymen, however, are very surprised. Some even find the payback incredible. Angus King, a producer and show host with public television in Maine, fell into that category. He was so impressed, in fact, that he felt the message should be taken before the nation at large via the TV screen.
So now Mr. King has his cameras rolling, recording every change the carpenters and insulation experts make in the 80-year-old house. A take-apart model, an exact scaled-down replica of the house, will be frequently used in the programs to help orient viewers to what is going on. Computer-screen displays will also help with the illustrating. Wing will host the show, which will eventually be offered free to the PBS network .
Why free? Because public TV isn't exactly flush with funds, King says, and the message must be delivered.
Wing points to a just-released report, ''World Energy Outlook,'' by the International Energy Agency. The conclusions of the agency are that world oil supplies will remain stable and plentiful through 1985, after which steadily rising world needs will see demand overtake supply.
Erratic and often-sharp increases in the price of oil will then follow unless further conservation and the development of alternative fuels have reached the stage where they can cushion the effects of the next oil shortage. As Wing sees it, those who insulate well now are not only improving their own financial situation but, in the long run, helping both the nation and the world at large.
The TV show, he says, will point out how relatively simple most energy-saving techniques are; how cost-effective retrofitting is, even when done by a contractor; and how many of the energy-conservation improvements family members can readily do themselves.
Besides cutting down on air infiltration (caulking and sealing) and heat transfer (insulating and adding thermal shutters to all windows), the Wings will boost the ''solar fraction'' (heat gained from the sun) of their home to 28 percent of the heat total. They will do this by adding sun-gathering windows to the south wall of the house and a sun room to the western wall. Getting the sun to provide more than a quarter of their heating needs is not bad for Maine - and is particularly good for a home that was not sited with solar energy in mind.
How will the show differ from other retrofit stories that have been aired recently? In several small ways, including the use of the computer, Wing says, but mainly in the cost of the alterations. Similar shows have concerned expenditures in the big leagues, costs in excess of $100,000. Consequently, they have had less relevance for the average person, Wing feels.
When the they bought the home, the Wings asked a real estate broker how much it would fetch on the open market if they made it ''the spiffiest house on the street.''
The broker replied: ''In this locality, no more than $75,000.''
Put another way, anything the Wings spent in excess of $25,000 on remodeling would be lost, should they ever wish to sell and move out. Thus, after a little calculating they found they could accomplish all that they wished and still stay