The solvent utilized in the electrospinning solution significantly impacts the morphology and thermal properties of PVA/PEG/Ag nanofibers. To prevent leakage of PEG, solid-liquid phase change, a suitable encapsulation method involves utilizing a combined single-phase electrospinning that incorporates PEG and supporting polymer of PVA. This study aims to investigate the production of thermal-regulating nanofibers from a solution containing PEG 6000, PVA, and AgNO3 precursor using electrospinning method. The influence of water and formic acid as a solvent on the morphology of the nanofibers was examined using SEM. The selected nanofiber characteristics and thermal performance were evaluated through FE-SEM, FT-IR, XRD, DSC, PCM leakage, and DTG tests. SEM images revealed that the formic acid-based nanofibers, consisting of two polymers and two polymer/Ag NPs, exhibited a nanoporous membrane, possibly due to enhanced cross-linking compared to water-based nanofibers. The results of the DSC indicated that fusion and solidification enthalpies of the selected water-based nanofibers were measured as 70.09 and −85.43 J/g, respectively. Unexpectedly, the DSC results indicated higher enthalpies compared to unheated samples. SEM image after thermal cycles, leakage results, and DTG of water-based nanofibers demonstrated their production with thermal stability, reliability, and the potential for creating shape-stable, thermally regulating fabricated nanofibers for various applications.