Commercial Water Heater Size Calculator
Determine the right commercial water heater size for your business based on peak demand and application type.
Commercial Water Heater Sizing Guide
Proper commercial water heater sizing requires understanding peak demand, temperature requirements, and specific application needs. Undersized units lead to shortages while oversized units waste energy.
Commercial Water Heater Types
| Type | Capacity Range | Best For | Pros | Cons |
|---|---|---|---|---|
| Storage Tank | 30-120+ gallons | Moderate, steady demand | Lower upfront cost | Standby heat loss |
| Tankless | 5-10+ GPM flow | Intermittent high demand | Endless hot water | Higher initial cost |
| Boiler | 300,000+ BTU/hr | Large facilities | High capacity | Complex installation |
| Heat Pump | 50-120 gallons | Energy-conscious | High efficiency | Climate dependent |
Peak Demand by Business Type
| Business Type | Gallons per Hour | Temperature | Peak Times |
|---|---|---|---|
| Restaurant | 30-100+ GPH | 140°F+ | Meal rushes |
| Hotel (per room) | 10-20 GPH | 120°F | Morning/evening |
| Laundromat | 50-200 GPH | 160°F | Weekends |
| Office Building | 2-5 GPH/person | 110°F | Start/end day |
Commercial Sizing Factors
1. First Hour Rating (FHR)
The most critical metric for storage tank systems:
- FHR = Recovery rate + (0.7 × Tank capacity)
- Must exceed peak 1-hour demand
- Example: 50 gal tank with 40 GPH recovery = 85 FHR
2. Temperature Rise Requirements
Commercial applications often need higher temperatures:
| Application | Minimum Temp | Recommended Temp |
|---|---|---|
| Handwashing | 100°F | 110°F |
| Showers | 105°F | 115°F |
| Dishwashing | 140°F | 150°F |
| Laundry | 120°F | 140°F |
| Sanitation | 160°F | 180°F |
3. Pipe Sizing Considerations
Commercial systems require proper pipe sizing:
- Minimum ¾" supply lines for most applications
- 1" or larger for high-demand facilities
- Consider recirculation systems for large buildings
- Insulate all hot water pipes
Frequently Asked Questions
How do I calculate peak demand for my business?
Three methods:
- Fixture count: Sum flow rates of all fixtures
- Usage patterns: Track actual consumption during peak
- Industry standards: Use GPH/person estimates
What's better for restaurants - tank or tankless?
Depends on:
- Tank: Better for steady demand (dishwashing)
- Tankless: Better for intermittent peaks (handwashing)
- Hybrid: Often ideal with tank for kitchen + tankless for restrooms
How many tankless units do I need for a hotel?
Consider:
- 1 unit per 10-15 rooms (point-of-use)
- Centralized systems need careful pipe sizing
- Factor in simultaneous shower use (morning peaks)
What size boiler do I need for a laundromat?
Calculation example:
- 10 washers × 3 GPH @ 160°F = 30 GPH
- Assume 50°F incoming: 110°F rise
- BTU = 30 GPH × 8.33 lbs/gal × 110°F = ~27,500 BTU/hr
- Add 25% safety factor: 35,000 BTU/hr minimum
Do commercial systems need water softeners?
Highly recommended for:
- All tankless systems
- Areas with hard water (7+ grains/gal)
- High-temperature applications
- To extend equipment lifespan