In order to simultaneously stabilize the shape and enhance the heat transfer efficiency of a typical polyethylene glycol (PEG) phase change material (PCM), a family of novel nanocomposites consisting of single-walled carbon nanotubes (SWCNs) and PEG was tailor-made via a facile impregnation method. The effects of SWCNs loadings ranging from 2% to 10% on the chemical structure, thermal performance and heat transfer enhancement of PEG were investigated experimentally. The fabricated nanocomposite exhibits high adsorption of PEG as high as 98% and can completely preserve its original shape without any PEG leakage even when subjected to a 400 melt-freeze cycle. The maximum adsorption of PEG is the highest value in literature up to now. The melting point of PEG/SWCNs nanocomposite shifts to a lower temperature while the freezing point shifts to a higher temperature while compared to the pure PEG, resulting in a substantial reduction of the supercooling degree. Above all, the thermal conductivity was found to increase with SWCN loadings whether in solid or liquid state. In detail, only with a small SWCN loading of 4%, a dramatically high, 375% enhancement is obtained in the solid state and a relatively high enhancement of 121% is achieved in the liquid state. (C) 2017 Elsevier Ltd. All rights reserved.