Harnessing hot electrons and holes resulting from the decay of localized surface plasmons in nanomaterials has recently led to new devices for photovoltaics, photocatalysis, and optoelectronics. Properties of hot carriers are highly tunable, and in this work, we investigate their dependence on the material, size, and environment of spherical metallic nanoparticles. In particular, we carry out theoretical calculations of hot carrier generation rates and energy distributions for six different plasmonic materials (Na, K, Al, Cu, Ag, and Au). The plasmon decay into hot electron–hole pairs is described via Fermi’s golden rule using the quasistatic approximation for optical properties and a spherical well potential for the electronic structure. We present results for nanoparticles with diameters up to 40 nm, which are embedded in different dielectric media. We find that small nanoparticles with diameters of 16 nm or less in media with large dielectric constants produce most hot carriers. Among the different materials, Na, K, and Au generate most hot carriers. We also investigate hot carrier-induced water splitting and find that simple-metal nanoparticles are useful for initiating the hydrogen evolution reaction, whereas transition-metal nanoparticles produce dominantly holes for the oxygen evolution reaction.