The Hydrogen Intermediate and Peak Electrical System (HIPES) is a new proposed system that uses low-cost off-peak electricity or base-load nuclear energy to economically produce electricity for peak electrical demand, spinning reserve, and power regulation. HIPES has three major subsystems. Hydrogen and oxygen are produced from water using (a) off-peak electricity by methods such as electrolysis or (b) steady-state hydrogen production methods such as nuclear-hydrogen production with thermochemical cycles. The two gases are stored in large underground facilities using the same technologies used for the seasonal storage of natural gas. Peak electricity is produced by an advanced steam turbine with a burner that combines stored H2, O2, and water to produce high-pressure 1500°C steam, which serves as feed to a special high-temperature steam turbine with actively cooled blades. The steam plant efficiency is ~70%. HIPES power outputs can be rapidly varied to match changing electricity demand because the slow-response component of a traditional steam system (the boiler) has been eliminated. The economics are based on (a) the low cost of large-scale underground gas storage, (b) a low-capital-cost efficient method to convert hydrogen and oxygen into peak electricity (no steam boiler), and (c) the large differences in the prices of base-load and off-peak power relative to the premium prices paid for peak power production, spinning reserve, and power regulation. The technology, markets, and economics are described.