The Centro de Investigación de Hidroponía y Nutrición Mineral (CIHNM) of the Universidad Nacional Agraria La Molina (UNALM) has designed, built and tested a modified DFT system for growing lettuce (Latuca sativa). It is made of local materials and saves 75% of electricity cost. The nutrient solution, which is recycled intermittently, is maintained in the channels at a depth of 2 cm instead of the usual 10 to 20 cm. This is accomplished by adjusting the height of inlets and outlets. A timer controls the pump so that it runs only 15 minutes per hour thus saving 16 hours electricity per day. When the pump is "off", the heigth of nutrient solution in the channels is 2 cm, so the roots are always in the nutrient solution without suffering stress. The modified DFT system was compared with a floating raft system to evaluate 7 heat tolerant lettuce cultivars (indoor: Atala, Lucile and Rapsody; outdoor: Crufia, Garuda, Senaria and Thirza) during the last El Niño phenomenon. This is the first evaluation of heat tolerant cultivars in a soilless culture in Peru and probably in South America. Although yields of the different summer cultivars were affected by high temperatures, none of the 7 cultivars bolted, so their cultivation could be recommended in Peru during hot weathers and in other countries with similar conditions. The Atala, Lucile and Thirza cultivars showed more growth and heat tolerance. There are lettuce cultivars that are more appropiate to be grown in DFT (Lucile & Senaria) and others in floating raft systems (Rapsody & Thirza). The Peruvian modified DFT model has given good results.