Solar fluid heater. The solar fluid heater comprises a solar collector having an evacuated glass tube of double walled construction comprising an inner absorber tube and an outer protective tube in spaced apart relationship with each other. One ends of the absorber and protective tubes are closed and the other ends of the absorber and protective tubes are sealed together . The space between the absorber and protective tubes is evacuated. An open ended working fluid flow tube is disposed within the absorber tube in spaced apart relationship with the absorber tube, The inner end of the working fluid flow tube is disposed in the proximity of the closed one end of the absorber tube and the outer end of the working fluid flow tube protrudes out of the other end of the absorber tube. A turbulator is located in the space between the absorber tube and working fluid flow tube over the working fluid flow tube along the length thereof in contact with the absorber tube and working fluid flow tube. The turbulator comprises a flexible wiry helical structure having a plurality of windings of a thermally conducting material wire arranged along the length thereof. The windings have a uniform diameter and are held together at a close pitch distance with a thermally conducting springy material holding wire running through the helical structure. A main header is partitioned into an inlet header and an outlet header by a partition wall . The outer end of the working fluid flow tube extends through the inlet header and is mounted in the partition wall and communicates with the outlet header. The inlet header communicates with the other end of the absorber tube. The space between the absorber tube and working fluid flow tube forms an inflow passage for the working fluid and the space within the working fluid flow tube forms an outflow passage for the working fluid.