THE main cost of washing clothes is not in the purchase of the washing machine, or the hot water or the detergent. It is, in fact, the hidden cost of wear and tear on clothes that are washed. Whitegoods' manufacturers Fisher and Paykel learned this when researching the needs of customers. In the long run, it can cost more to replace shrunken sweaters and torn shirts than the cost of the machine purchase and weekly hot water and detergent bills. Fisher and Paykel have taken what they learned and introduced a ''clothes care'' philosophy, which they incorporated into the design of their washing machines and clothes dryers. The dryers have a pressurised cabinet system with technology that is licensed to major manufacturers around the world. Fisher and Paykel have taken just as much care in the room which is the focus of the home - the kitchen - where many white products play an important role. Company engineers and designers set out to make refrigerators, freezers and electric ranges to complement modern kitchen trends. An integral part of the Fisher and Paykel development process is the concept of ''food care''. This ensures that, right from the start, the ability of the refrigerator to store food correctly, or for an oven to remain at the correct temperature, is an integral part of the product's development. Fisher and Paykel is based in New Zealand. Whitegoods account for about half the company's business, of which almost 50 per cent is exported.