When selecting Ariston water heaters, buyers must prioritize heating technology and tank capacity. For electric models, ensure the presence of Titanium-shielded heating elements which offer superior corrosion resistance. For gas models, verify the Energy Factor (EF) rating to ensure high thermal efficiency. It is critical to match the tank volume (ranging from 10L to 500L) with the intended occupancy; for instance, a 30-50L unit is standard for single-bathroom apartments, while 100L+ units are required for multi-point high-demand scenarios.