Sizing primer: capacity, FHR, BTU input, recovery time
Choosing a water heater is fundamentally a sizing problem — match the equipment to your household's hot water demand. Four numbers actually drive the decision: tank capacity (gallons), first-hour rating (gallons delivered in one hour), BTU input (how fast the unit can reheat), and recovery time (gallons of hot water produced per hour from cold). The trick is understanding which number matters most for your household.
For most Tulsa metro households, a 50-gallon gas tank covers a family of four comfortably. But size alone isn't the full picture — first-hour rating (FHR) tells you how much hot water the unit can actually deliver in the first hour of use, which matters if your household runs multiple hot water draws simultaneously.
Rarely run multiple draws at once
Moderate simultaneous hot water use
High demand, consider tankless
| Household size | Tank capacity | First-hour rating | Recovery — gas | Recovery — electric |
|---|---|---|---|---|
| 1–2 people | 30–40 gal | 42–55 gal/hr | 30 gph @ 90°F rise | 15 gph @ 90°F rise |
| 3–4 people | 40–50 gal | 55–72 gal/hr | 32–40 gph @ 90°F rise | 18–22 gph @ 90°F rise |
| 5+ people | 50–80 gal | 72+ gal/hr | 40+ gph @ 90°F rise | 22–25 gph @ 90°F rise |
| Tankless (any size) | On-demand | ~6–11 GPM sustained | No recovery time — heats on demand | |
We do a household assessment on every installation — not just to sell a bigger unit, but to make sure you're not paying for capacity you'll never use. Get a free sizing estimate →
Gas vs. electric vs. hybrid heat-pump
Fuel type is the first big decision — and it's largely constrained by what your home already has. Gas requires a gas line and venting. Electric only needs a 240V circuit. Hybrid heat-pump uses electricity but moves heat rather than generating it, cutting energy use roughly in half — at the cost of higher upfront price and stricter installation requirements.
| Factor | Gas (natural gas / propane) | Electric | Hybrid heat-pump |
|---|---|---|---|
| Heating technology | Burner combustion | Resistance heating elements | Heat pump (moves ambient heat) |
| BTU input / capacity | 30,000–50,000 BTU/hr | 4,500–5,500W @ 240V | ~3,500W compressor |
| Recovered efficiency / UEF | UEF 0.60–0.72 | UEF 0.90–0.95 | UEF 3.0–4.0 |
| Upfront installed cost | $1,950 (tank) / $4,200 (tankless) | $1,400–$1,800 (tank) | $3,200–$4,500 (tank) |
| Operating cost (Tulsa, family of four) | ~$600–$800/yr | ~$900–$1,200/yr | ~$350–$500/yr |
| Installation requirements | Gas line + venting (direct/power/atmospheric) | Dedicated 240V circuit (30A) | 240V circuit + condensate drain + ≥700 cu ft air + ≥40°F ambient |
| Cold-climate performance | Unaffected — burner heat output is constant | Unaffected — elements produce same heat always | Recovery slows as garage temps drop below 40°F (Tulsa winter risk) |
| Best for | Homes with existing gas service; budget-first lifetime cost | Homes without gas line; simple install priority | Conditioned-space homes with high electric rates; long-term efficiency focus |
Oklahoma electric rates (typically 10–13 ¢/kWh) are lower than the national average, which narrows the operating-cost advantage of hybrid heat-pump vs. electric in this market. Gas remains the lowest-cost option to operate in the Tulsa metro for most households. If you're choosing electric (no gas service available), hybrid heat-pump is worth the premium — it cuts electric bills nearly in half. If you have gas service, the lifetime math usually favors a high-efficiency gas tank or tankless unit.
For a deeper look at the tankless option itself, see our Tankless Installation Guide → covering gas line requirements, venting types, and flow rate sizing.
Tank vs. tankless: which fits your home?
Both work. Neither is universally better — the right choice depends on your household size, budget, and how you use hot water.
| Factor | Standard Tank | Tankless |
|---|---|---|
| Upfront cost | $1,950 installed | $4,200 installed |
| Lifespan | 8–12 years | 15–20 years |
| Energy savings | Standard efficiency | 20–30% less energy use |
| Hot water capacity | Limited by tank size, but consistent | On-demand, but limited flow rate (GPM) |
| Failure mode | Tank leak at end-of-life (flooding risk) | Heat exchanger scale damage (no leak) |
| Maintenance | Annual flush, anode rod every 2–3 years | Descale every 1–2 years (Tulsa hard water) |
| Best for | Normal households, budget-first buyers | Large households, long-term thinkers, off-grid homes |
Oklahoma's hard water affects both types differently. Sediment buildup shortens tank life faster here than in softer-water markets. Tankless units need periodic descaling — annually in the Tulsa metro, rather than the 2–3 year interval recommended elsewhere. Either way, budget for hard water's accelerated maintenance schedule when sizing your decision.
For a family of four running normal loads, either option works well. If you have multiple people showering simultaneously or want to eliminate standby heat loss long-term, tankless is the better investment. See our full tank vs. tankless comparison →
First-hour rating and recovery time explained
First-hour rating (FHR) is the single most useful number on the Energy Guide label when you're choosing between tank units of the same capacity. It tells you how much hot water the unit can deliver in the first hour starting with a full tank, including both stored hot water AND recovery from cold. Two 50-gallon gas tanks can have very different real-world capacities based on burner size.
40–50 gallon gas tanks
per hour, 90°F rise
per hour, 90°F rise
How to use FHR in practice: Add up the gallons of hot water your household uses in the busiest hour. If it's 60 gallons and you're choosing between a 50-gallon tank with FHR of 55 gal/hr and one with FHR of 72 gal/hr, the latter covers your morning routine without running cold. The first tank runs out when the burner can't keep up with two simultaneous showers plus a dishwasher.
Recovery time and BTU input: A tank unit's recovery speed depends on burner size (BTU/hr input). A 30,000 BTU/hr burner reheats a 50-gallon tank from cold in roughly 35–40 minutes. A 50,000 BTU/hr burner does it in roughly 22–25 minutes. For large households, faster recovery means shorter waits between back-to-back hot water draws. For small households, recovery speed matters less. Don't pay a premium for higher BTU input you don't need.
Higher BTU input doesn't always cost more to operate. A high-input burner runs for less time per duty cycle, so the cumulative energy use can be similar. Look at the Energy Factor (EF) or Uniform Energy Factor (UEF) on the yellow label — that's the actual efficiency number, accounting for standby losses. A standard 50-gallon gas tank ranges UEF 0.60–0.72; a high-efficiency condensing gas tank can hit UEF 0.85+.
Want to know what FHR your existing unit is rated for and whether it's the right size for your home? We can assess that as part of any service call. Request an assessment →
Hybrid heat-pump water heaters: when do they pay off in Oklahoma?
Hybrid heat-pump water heaters (also called HPWHs) are the most efficient electric option on the consumer market — they use roughly half the energy of a standard electric tank. Instead of generating heat directly with a heating element, a heat pump compresses refrigerant to move heat from the surrounding air into the water. The catch is the installation environment: HPWHs need space, ambient warmth, and a condensate drain.
vs. UEF 0.90–0.95 standard electric
family of four in Tulsa
vs. standard electric
Federal IRA tax credit: Many HPWHs are eligible for a federal tax credit under the Inflation Reduction Act. Credit amounts and eligible model lists change periodically — verify current status on the Energy Star certified HPWH list before purchase. Credits can be substantial (sometimes 30%+ of the equipment cost), so confirm eligibility and current documentation requirements with a tax professional before claiming.
Where HPWHs work — and where they don't
HPWHs work best in conditioned space — basements, utility rooms, finished garages kept above 40°F year-round, or interior closets adjacent to living space. They need roughly 700 cubic feet of surrounding air (about a 10×10 ft room with adequate ventilation) so the heat pump has warm air to extract. A condensate drain is required for the dehumidification moisture the heat pump pulls from the air. Most HPWHs also include a resistive element as backup for high-demand periods.
Unheated garage installs in Tulsa can drop below 40°F in winter — at that point, the heat pump's efficiency drops and recovery slows significantly. The resistive backup kicks in but you've lost the energy savings. If your only installation option is an unconditioned garage, plan for it to remain above 40°F year-round (insulate, add a small heating element, or relocate the unit). Tight utility closets without adequate air volume starve the heat pump and force it into resistive mode constantly. A standard electric tank is the better fit for those locations.
If you don't have gas service, a hybrid heat-pump is the next best thing — particularly for households in conditioned space who use a lot of hot water. If you do have gas service, the math usually still favors gas for total lifetime operating cost. We can evaluate which path makes sense for your home and your utility arrangement. Get a free quote →
Frequently asked questions
Need help picking the right water heater?
We'll assess your household demand, walk you through the tank vs. tankless and fuel-type tradeoffs, and give you a straight quote — no sales pitch. Serving the Tulsa metro.