Compliance with harmonic limits is a significant concern for suppliers and consumers of electrical energy. A conventional application of IEEE 519-1992 requires users to limit harmonic currents while suppliers limit harmonic voltages. In a competitive arena, this approach could lead to denial of service and loss of revenue due to (indirect) conservatism in the existing limits. In addition, conventional harmonic studies using known load current spectra may be impossible due to the presence of a third-party re-seller or load aggregator. In this paper, limit compliance is considered based on the question of "How much harmonic current is required to produce a limiting amount of harmonic voltage?" Formulas are developed that relate voltage limits to current limits as a function of system impedance. These formulas: 1) allow the maximum harmonic-producing load to be estimated without conducting a specific harmonic study and 2) indicate the degree of conservatism in existing limits