Installing a new water heater is one of those home upgrades everyone needs—but few people fully understand. One of the most common questions homeowners ask is: how long does water heater installation really take? The answer depends on several factors, including the type of unit, your home’s plumbing setup, and whether repairs or upgrades are required. In this guide, we’ll break down realistic installation timelines, explain what can slow things down, and help you know when to call a professional for water heater repair or replacement.