Why Pair Two Heater Types?
Natural-gas storage heaters are workhorses: they heat large volumes of water cheaply, but during rush periods the tank can’t recover fast enough and the outlet temperature may dip below the 140 °F (60 °C) often required for food-service sanitation.
Electric tankless units, installed just before the most demanding fixtures, add instantaneous BTUs only when flow is detected. Together you get the best of both worlds:
| Benefit | How the combo delivers |
|---|---|
| Guaranteed hot water at code temperatures | Storage unit pre-heats; booster tops-off to a precise setpoint, even if the tank cools. |
| Lower operating cost | Gas handles ~90 % of daily BTU load at a lower $/BTU; the electric element runs only for last-mile fine-tuning. |
| Reduced heater size | Because peak-demand spikes are trimmed by boosters, the central tank can be sized for average—not worst-case—load. |
| Shorter pipe runs = less waste | Boosters mount within a few feet of dishwashers, prep-sinks, or rest-rooms, cutting standby losses in long recirculation loops. |
| Redundancy | If either unit requires maintenance, the other can maintain limited hot-water service. |
Where This Strategy Shines
- Restaurants, cafeterias & breweries – Health codes mandate 140 °F sanitizing water or 180 °F rinse temps. Boosters nail that last 10–20 °F.
- Hotels & multi-family – Late-night showers after laundry cycles won’t run cold.
- Salons & medical offices – Precise temperature control at individual suites or procedure rooms.
Sizing & Design Checklist
- Estimate peak flow at each boosted fixture (GPM × desired ΔT).
- Size the storage tank for ~70 % of daily demand or the largest fill-draw cycle—whichever is greater.
- Select booster wattage so
kW = (GPM × ΔT × 500) / 3412. Example: 2 GPM boost from 120 °F to 140 °F ⇒ 5.9 kW unit. - Electrical service – Confirm 240 V circuits with adequate amperage; most commercial boosters need 30–60 A.
- Mixing valves/tempering – To comply with scald-protection codes, add thermostatic mixing downstream if fixture temp must be lower than 140 °F.
- Recirculation strategy – Loop to the tank only; boosters don’t need constant flow and will fire on demand.
- Ventilation & combustion air – The gas tank still needs code-compliant venting; tankless electrics do not.
Installation Tips from Oasis Plumbing Co.
- Mount boosters vertically to protect heating elements and simplify service access.
- Isolate with full-port valves so either unit can be serviced without shutting down the building’s hot-water supply.
- Use stainless flex connectors rated for 180 °F to resist scale and corrosion.
- Add sediment filtration upstream; tankless elements foul quickly if debris slips past.
- Program booster setpoint 10–15 °F higher than the storage tank to avoid “see-saw” temperature hunting.
Operating Cost Snapshot
A Denver-area fast-casual kitchen using 200 gallons/day at 140 °F can save 15-25 % on annual water-heating energy versus an all-electric tankless array while eliminating lunchtime cold-water dips typical with a standalone 75-gal gas heater.
Rule of Thumb: Every degree you pre-heat with gas is 3–4× cheaper than the same BTU delivered with electricity—use the booster only for the narrow temperature band you truly need.
Maintenance & Lifecycle
| Component | Maintenance interval | Common tasks |
|---|---|---|
| Gas storage heater | 6–12 months | Flush tank, inspect anode rod, test T&P valve |
| Tankless booster | 12 months | Descale heat exchanger with food-grade vinegar, clean inlet screen |
| Crossover valves | 5 years | Replace gaskets & check mixing accuracy |
Combined systems typically out-live single technology installations by 2–3 years because the load is shared and each unit cycles less aggressively.
Ready to Upgrade?
Oasis Plumbing Co. designs, installs, and maintains hybrid hot-water systems across Colorado. We handle sizing calculations, electrical coordination, and health-department paperwork so you can focus on running your kitchen—not the water heater.
Questions about capacity, payback, or code compliance?
Call us at (303) 555-0147 or schedule a site visit online.