Picking the wrong size water heater is one of the most expensive mistakes a homeowner can make. Too small and you’re cold by the second shower. Too big and you’re paying to heat water you never use — every single month.
Here’s how to get it right.
Start With How Many People Live in Your Home
Tank water heaters are sized by gallon capacity. The standard breakdown most plumbers use:
- 1–2 people: 30–40 gallon tank
- 3–4 people: 40–50 gallon tank
- 5+ people: 50–80 gallon tank
These are starting points. Your actual usage habits, fixture count, and home size all affect the real number.
Tank vs. Tankless: The Sizing Rules Are Different
If you’re shopping for a tankless water heater, forget gallons. Tankless units are rated by flow rate — measured in gallons per minute (GPM). You need to estimate how many fixtures might run at the same time. A shower uses roughly 2 GPM. A dishwasher runs around 1.5 GPM. Two showers running simultaneously means you need at least 4 GPM at minimum.
Most homes in the Treasure Coast do well with a unit rated between 6–9 GPM. According to the U.S. Department of Energy, tankless heaters can be 24–34% more energy efficient for homes using 41 gallons or less per day — which makes them worth the higher upfront cost over time.
The Number Most Homeowners Ignore: First Hour Rating
For tank units, the First Hour Rating (FHR) tells you how much hot water the heater can produce starting from a full tank during the first hour of heavy use. This matters more than tank size alone. A 50-gallon tank with a high FHR outperforms a 50-gallon tank with a low one every time.
To figure out your peak hour demand, add up everything running during your busiest morning — showers (about 12 gallons each), dishwasher (6 gallons), laundry (7 gallons). That total is the FHR you need to meet or beat when comparing units.
Florida Homeowners Have One Extra Variable
Incoming groundwater in Treasure Coast runs cooler than most people expect, especially in winter. Cooler inlet water makes your heater work harder to hit your target temperature. This is why homeowners who size by national charts sometimes still end up slightly undersized.
If you’re on the edge between two sizes, go one tier up. Our team factors this in on every water heater replacement — it’s one of the first things we ask about.
When the Problem Isn’t the Water Heater — It’s the Size
If your current unit constantly runs out of hot water, the problem might not be age. It could be that your family has grown since the unit was installed. Common reasons to upsize rather than just replace:
- You added a bathroom or bedroom
- Kids moved back home
- You’re working from home now (more showers, more laundry)
- You switched to a larger soaking tub
A water heater repair can fix a performance issue, but if the unit was undersized to begin with, you’re just patching a bigger problem.
Get Sized Right the First Time
Size matters more than brand. Get it wrong and you’ll either spend years on high energy bills or have the same argument every morning about who used all the hot water.
Contact Discount Water Heaters and we’ll size it correctly before anything gets installed.
✓ Same-day service available ✓ Upfront pricing — no surprises ✓ Licensed technicians ✓ Warranty on all work
📞 Call or text: 772-202-6671