Prospective house purchasers are having increasing difficulty qualifying for mortgage loans due to high interest rates. To that, add high energy costs.

The Federal Home Loan Mortgage Corp., which makes a secondary market in mortgages, recently found that 59 percent of the 4,000 lenders it surveyed consider energy costs when deciding whether a loan application should be approved. They may figure in average monthly utility bills along with taxes and insurance payments when determing if the householder has enough income to make payments.

Or lenders may keep the debt-to-income ratio lower, say to 25 percent, if the house has high fuel bills. In case of a low down payment, and therefore a riskier loan, energy costs may be looked at more closely.

The survey also found that 12 percent of the lenders had mortgage delinquencies or foreclosures that could be attributed to high energy costs.

In other words, some pressed owners paid their fuel bills instead of their mortgages and, as a consequence, risked losing their homes. However, just 2 percent of the lenders identified high energy costs as a frequent factor in late payments or defaults; 79 percent said they were rarely the cause.

Another survey question showed a still larger number, 68 percent, instruct apraisers to include the energy efficiency of a house in its appraised value. Energy-saving features like adequate insulation and heat pumps help increase a dwelling's worth.

Fewer than a third of the lenders surveyed will make energy-related home improvement loans in combination with first mortgages. Such loans are generally unsecured loans made at higher rates.

Four out of five grant loans for active and passive solar systems. Yet only one in 10 will take solar systems and other energy saving devices into account by offering better loan terms.