Sizing
What Size Water Heater Does a Denver Home Need?
Tank capacity is a poor predictor of whether you run out. First-hour rating is the number that matters.
Published 2026-06-17 · Denver Water Heater Service Center
Most people replace a 50-gallon heater with a 50-gallon heater and hope. Sometimes that is right. But if you were running short before, or the household has changed, sizing deserves ten minutes.
Count your peak hour, not your day
What matters is the busiest sixty minutes — usually weekday mornings. Add it up:
| Use | Hot water consumed |
|---|---|
| Shower (low-flow, 8 min) | About 14–16 gallons |
| Shower (older head, 8 min) | About 20–26 gallons |
| Filling a 60-gallon soaking tub | About 40 gallons |
| Dishwasher cycle | About 6 gallons |
| Clothes washer, warm | About 7–12 gallons |
| Shaving or hand washing | About 2–4 gallons |
Match it to a first-hour rating
Every tank has an FHR on its EnergyGuide label — the gallons it can deliver in one hour starting fully hot. It combines storage with recovery rate, which is why a 40-gallon gas heater can out-deliver a 50-gallon electric one. Aim for an FHR at or slightly above your peak hour.
| Household | Peak hour | Gas tank | Electric tank | Tankless (January) |
|---|---|---|---|---|
| 1–2 people, one bath | ~30 gal | 30–40 gal | 40 gal | 5.0–6.6 GPM |
| 3–4 people, two baths | ~45 gal | 40–50 gal | 50–66 gal | 6.6–8.0 GPM |
| 5+ people or a soaking tub | ~65 gal | 50–75 gal | 80 gal | 8.0–9.8 GPM |
| Two simultaneous showers | ~55 gal | 50 gal high-recovery | 80 gal | 9.0+ GPM |
The Denver winter adjustment
Recovery rate is quoted at a 90-degree rise. In January, Denver inlet water in the low 40s means a heater must lift water nearly 80 degrees to reach 120°F — so real-world recovery in winter is slower than the label, and tankless output drops by roughly 40 percent against brochure figures. If you size for a Denver February, September takes care of itself.
Do not just buy bigger
An oversized tank costs more upfront, occupies more space, and loses standby heat you never use. Three better moves when mornings are tight: choose a high-recovery model in the same physical footprint; stagger shower times by fifteen minutes; or, if you genuinely need continuous supply, go tankless.
Measure before you order
Efficiency standards changed tank dimensions in 2015, so a modern 50-gallon unit can be several inches taller and wider than the one it replaces. Check the door opening, the closet header, the vent clearance above and the drain pan diameter. We measure on every quote — it is the most common cause of a failed install day.
Questions about your own water heater? Call 720-735-8936 — we answer 24 hours a day and we are happy to talk through a problem whether or not it turns into a job.
Cold shower this morning? We can be out today.
Tell us what the heater is doing and we will give you a straight answer on the phone — repair, replace, or wait.