ABSTRAK Evaporasi merupakan proses penghilangan sebagian besar air pada bahan dengan cara memberikan panas pada titik didihnya menggunakan evaporator. Proses evaporasi menghasilkan uap air yang dapat dimanfaatkan untuk pembangkitan proses serupa. evaporator double effect termodifikasi merupakan alat evaporasi dengan proses penguapan berganda dan bekerja pada tekanan dibawah 1 atm. Energi uap yang dihasilkan dari penguapan bahan di ruang proses 1 (efek 1) akan digunakan untuk pemanasan  bahan  di  efek  2.  Tujuan  penelitian  adalah  melakukan pengujian pada aspek teknis terutama efisiensi energi dari mesin evaporator double  effect  termodifikasi pada bahan nira tebu. Pengukuran  dan  pengamatan  pada  proses evaporasi dilakukan  terhadap  data suhu  bahan  dan  uap,  tekanan  vakum,  volume bahan, konsumsi bahan bakar, rendemen giling sementara batang tebu, dan pengurangan volume bahan. Pencatatan suhu, tekanan, dan volume dilakukan setiap 10 menit. Hasil pengamatan suhu titik didih bahan didapatkan sebesar 63,4 oC pada tekanan rata-rata sebesar -60 CmHg. Pengamatan konsumsi bahan bakar menunjukkan bahwa pada 5 jam 20 menit proses rata-rata sebesar 21.312 kJ/jam. Pada efek 1 rata-rata presentase pengurangan kadar air sebesar 54% sedangkan pada efek 2 sebesar 20,7%. Didapatkan nilai efisiensi rata-rata sebesar 56,3%.Kata Kunci : Efisiensi; Evaporator Double Effect; Evaporasi; Nira Tebu   ABSTRACTEvaporation is a process removing most of the water in a material by giving heat till boiling point using an evaporator. The evaporation process produces water vapor that can be used for generating similar processes. Modified double effect evaporator is an evaporation tool with multiple evaporation processes and works under pressure 1 atm. The steam energy generated from the evaporation of material in process chamber 1 (effect 1) will be used to heat the material in effect 2. The purpose of this research is to test the technical aspects, especially the energy efficiency of the modified double effect evaporator on the sugar cane juice. Measurements and observations on the evaporation process are carried out on data of material temperature and vapor, vacuum pressure, material volume, fuel consumption, temporary milled yield of sugarcane, and reduction in material volume. Recording temperature, pressure, and volume is recorded every 10 minutes. Observation of material boiling point temperature was 63.4 oC and average pressure was -60 CmHg. The results of observations of fuel consumption showed that in about 5 hours 20 minutes the average process was 21,312 kJ / hour. In effect 1 the average reduction in water content was 54% while in effect 2 it was 20.7%. Obtained an average efficiency value of 56.3%.Keywords: Double Effect Evaporator; Efficiency; Evaporation; Sugarcane Juice