A 45° parallel-plate energy spread analyzer has been designed and built for the ISAC project at TRIUMF. It features an energy resolution of⩽0.04&percent;and a spectrometer constant ofk=1.29.Nineteen 0.1 mm by 10 mm metal guard frames with 1 M&OHgr; resistors are used to equalize the electric field in the analyzer to an order of⩽0.5&percent;.Electric field simulation is done by a codePOISSON. This article describes the design of the analyzer. Preliminary experimental results are also presented. ©1998 American Institute of Physics.