Lightning is observed on all four Solar System giant planets; these observations can illuminate atmospheric structure in unique ways, but this relation requires interpretation. I present a computationally light, one-dimensional model of atmospheric convection and electrification and apply it to the Solar System giant planets. On Jupiter and Saturn, lightning observations are well-matched by the model; on Uranus and Neptune, existing observations are limited to the Voyager 2 flybys, and perspectives for future measurements are described instead. While quantitative results are imprecise, a number of strong qualitative results are demonstrated. On Jupiter, a dissolved antifreeze – presumably ammonia – in the water clouds is necessary to explain lightning observations. The vertically spread lightning distribution of Jupiter is replicated, and predicted to be matched on Saturn, Uranus, and Neptune, though shifted deeper on those planets. The best observable for constraining Jovian and Saturnian water abundance through lightning is the altitude of the deepest flashes. Anhydrous ammonia clouds are not predicted to substantially affect lightning on Jupiter and Saturn, but may play a large role in Uranian and Neptunian lightning, depending on the strength of the triboelectric effect under these conditions. From the model and comparisons to Jupiter, the Uranian and Neptunian lightning sferics observed by Voyager 2 are either deep lightning attenuated by the atmosphere between it and the spacecraft, or horizontally limited shallow lightning; a future Uranus Orbiter could resolve this question by attempting to detect an optical signal.