Heat Pump Water Heater vs Gas: Efficiency, Yearly Cost, Installation, and What Each Needs in an Outage

EcoFlow- 2026/10/20

Table of contents

A gas water heater can leave you without hot water during a blackout, even when your gas supply is working. Power-vent and tankless models need electricity for their fans, ignition systems, or controls, while some traditional gas tanks with standing pilots can keep heating without an outlet. Heat pump water heaters also need electricity, but they use it differently and can be much more efficient. Here's how the options compare on energy costs, installation, recovery time, and outage readiness, including where EcoFlow TITAN Plus and EcoFlow TITAN Classic may fit.

Heat Pump Water Heater vs Gas Water Heater: Quick Comparison Table

A gas water heater burns natural gas or propane to heat water. A heat pump water heater uses electricity to pull heat from the surrounding air and transfer it to the tank, with electric resistance elements available for backup on many models. The right choice depends on your utility rates, available space, installation costs, and whether you need hot water during a power outage.

Feature	Heat pump water heater	Gas storage water heater
Energy source	Electricity	Natural gas or propane
How it heats	Compressor moves heat from room air; resistance elements for high demand	Burner under the tank
ENERGY STAR minimum UEF	3.30 (integrated); 2.20 on a 120V/15A circuit	0.81 (medium draw, >20 to ≤55 gal); 0.86 (high draw or over 55 gal)
Example model UEF	Rheem ProTerra 50 gal, 30A: 3.88	Rheem Professional Classic Plus atmospheric 40 gal: 0.66 (series 0.58 to 0.66)
First hour rating example	Rheem ProTerra 50 gal, 30A: 67 gallons per hour	Rheem atmospheric series: 52 to 105 gallons (series range)
Venting	None; needs air volume and a condensate drain	Chimney or vent pipe required
Electrical need	240V/30A on many full-size models; some 120V plug-in models	Atmospheric: no outlet needed (Rheem); power vent: "Requires electricity to operate" (Rheem)
Combustion on site	No	Yes; yearly service and CO alarms (CDC, CPSC)

Not all gas water heaters work the same way during an outage. As explained in this guide to whether a gas water heater needs electricity, the answer depends on its ignition and venting design. This difference also determines whether you need backup power to keep hot water available.

Which Water Heater Needs Power in an Outage? Where EcoFlow TITAN Plus and EcoFlow TITAN Classic Fit

A heat pump water heater runs on electricity, so it needs a suitable backup system to operate during a blackout. Gas models vary: some need power for a fan, ignition, or controls, while a traditional atmospheric tank with a standing pilot may continue working without electricity.

Water heater type	Needs house power?	What to check	Backup that may fit
Atmospheric gas tank with standing pilot	No outlet needed (Rheem: atmospheric models install "without the need of an electrical outlet")	Confirm the model has no power cord or electronic ignition	None needed for the water heater
Power vent gas tank	Yes: "an electric blower" that "Requires electricity to operate" (Rheem)	Blower, igniter, and control wattage on the label; confirm 120V	EcoFlow TITAN Classic for that 120V circuit, while gas supply is normal
Gas tankless	Yes: "120 volts AC, 60 Hz and less than three amps" (Rinnai)	Fan and control requirement in the manual; gas line size	EcoFlow TITAN Classic for that 120V circuit, while gas supply is normal
Heat pump water heater, 240V	Yes: Rheem 30A ProTerra (PROPH50 T2 RH400-30) lists 208 to 240V, 4,500W dual backup elements, 21.0 max running amps, and requires a dedicated 30A circuit breaker.	Compressor draw in heat pump mode, element wattage in hybrid or electric mode, starting load	EcoFlow TITAN Plus, if the load and other backed-up circuits are compatible
Heat pump water heater, 120V plug-in	Yes: A.O. Smith Voltex 120V lists 9.38 amps on a shared 15A circuit	Circuit and simultaneous loads	Either system, matched by an electrician

Backup options with EcoFlow TITAN

Heat pump water heaters: The EcoFlow TITAN Plus can back up a compatible heat pump water heater circuit through the 240V version of the Smart Home Panel 10. Before installation, ask a licensed electrician to check the 4,500W auxiliary heating element on applicable 30A Rheem models, the compressor's starting load, and how long you need hot water during an outage.

Gas water heaters: The EcoFlow TITAN Classic can support compatible 120V fan, ignition, or control circuits that require electricity, provided the gas supply remains available. It connects through the 120V version of the Smart Home Panel 10, installed by a licensed electrician. It does not supply gas or power a 240V heat pump water heater.

Estimated runtime

These estimates assume 85% usable battery energy after conversion losses. Actual runtime depends on the heater's power draw and operating cycle.

Gas tankless water heater: While Rinnai’s official FAQ specifies up to 3A at 120V (360W), power consumption varies by operating state, including standby draw, active combustion fans, freeze protection, and optional recirculation pumps. Based on a maximum 360W draw, the EcoFlow TITAN Classic's 5 kWh base battery (assuming 85% usable energy) provides an estimated 11.8 hours of runtime. This calculation is a planning estimate; actual runtime depends on your specific model's operational mode and whether features like freeze protection are active.
Heat pump water heater: If a 4,500W resistance element runs continuously, the EcoFlow TITAN Plus's 5kWh base battery provides approximately 0.9 hours of element runtime. Heat pump-only operation draws much less power; check the heater's nameplate for its actual demand.

These are planning estimates, not compatibility guarantees for specific water heater models. These runtime estimates offer a starting point, but the right setup depends on your water heater's electrical requirements. Compare the EcoFlow TITAN Plus and EcoFlow TITAN Classic below to see how their voltage, output, and capacity differ.

EcoFlow TITAN 5000 Plus

•100% Whole-Home Backup. 7.2–10kW output and 5kW single-circuit capacity power your 3-ton AC, refrigerator, and the rest of your home simultaneously, with no soft starter required. • 100% Whole-Home Savings. Save up to $4,000 per year, with ROI in as little as 3 years. • Only 30% of Traditional System Cost. Industry-first 200V architecture, custom high-rate LFP cells, and a pre-wired SHP10 help lower costs across the entire lifecycle, from upfront purchase and installation to long-term use. •OASIS 3.0 — Your AI Home Energy Manager. Charges off-peak, powers your home during peak hours, and helps lower your electricity bill every day. •Built to North America’s Highest Safety Standards. UL 9540A tested and UL 9540 certified, with EV-grade LFP cells and 24/7 BMS monitoring.

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For essential 120V circuits, the EcoFlow TITAN Classic offers a simpler backup option, with 4kW output and expandable capacity up to 30kWh.

EcoFlow TITAN 5000 Classic

•4,000W Whole-Home Essential Power. Run your fridge, microwave, Wi-Fi, lighting, and CPAP all at once. • 5–30kWh Expandable Capacity. Get 1 day to 1 week of essential backup. Add batteries anytime, with no installer needed. • <25 dB. Quiet enough for indoor use—quieter than a whisper. • ≤20 ms Automatic Switchover. The lights don’t even flicker. • OASIS 3.0 — Your AI-based Home Energy Manager. Charges off-peak, powers your home during peak hours, and helps lower your electricity bill every day.

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The EcoFlow TITAN Plus can back up a compatible heat pump circuit, subject to checks for wattage, starting load, and runtime. The EcoFlow TITAN Classic supports compatible 120V gas heater controls if the gas supply remains available. Standing-pilot atmospheric gas tanks may need no battery. Ask a licensed electrician to confirm compatibility and account for starting versus running watts. Beyond outages, compare efficiency, UEF ratings, and the 2029 federal standard.

Efficiency compared: UEF, ENERGY STAR thresholds, and federal standards

Uniform Energy Factor (UEF) measures water heater efficiency under standard test conditions. Heat pumps can exceed 3 by transferring heat, while gas models typically score below 1 due to exhaust and standby losses. ENERGY STAR minimums, checked October 14, 2026, are 3.30 for integrated heat pumps, 2.20 for 120V/15A heat pumps, 0.81 or 0.86 for gas storage models depending on draw rate, and 0.95 for gas tankless models. The Department of Energy says heat pumps can be two to three times more efficient than conventional electric resistance heaters, not necessarily gas models. Standing-pilot gas units also consume fuel continuously to keep the pilot burning.

Federal water heater standards

Finalized in 2024, the updated federal standards require covered manufacturers to comply on and after May 6, 2029. Most common-sized electric water heaters will need heat pump technology to meet the requirements, while gas-fired and other storage models face more moderate efficiency increases.

Rule	What it covers	Status	Source
Consumer water heaters final rule (89 FR 37778, May 6, 2024)	Electric, gas, and oil storage water heaters; most common-size electric tanks reach heat pump efficiency levels	Final; compliance May 6, 2029	DOE Consumer Water Heaters page; Federal Register
Gas-fired instantaneous (tankless) final rule (89 FR 105188, Dec. 26, 2024)	Gas tankless efficiency	Disapproved by Congress under the Congressional Review Act (resolution signed May 9, 2025); withdrawn by DOE May 20, 2025 (90 FR 21390); DOE "is still considering" amended standards	Federal Register 2025-09030; DOE Spring 2025 Unified Agenda

The 2029 federal standards raise efficiency requirements for water heaters but do not ban gas models. UEF helps compare efficiency, while converting watts to BTU per hour helps compare electric heating loads with gas burner ratings. Efficiency affects energy use, but local electricity and gas prices determine which heater costs less to run.

Operating Cost: Electricity vs Natural Gas at 2025 National Prices

A heat pump water heater uses less energy than a gas model, but the annual cost depends on your local utility rates. This example uses 2025 national average prices and the Department of Energy's standard water-heating test conditions to illustrate the difference. The Energy Information Administration reported an average residential electricity price of 17.3 cents per kWh in 2025. The average residential natural gas price was $15.34 per thousand cubic feet, or about $1.48 per therm using the EIA conversion factor.

Estimated yearly water heating cost

For this example, the DOE's medium-use test pattern assumes 55 gallons of water heated each day from 58°F to 125°F. That's about 30,733 Btu of heat per day, or 11.2 million Btu per year. To estimate the energy cost, divide the annual heat required by the water heater's Uniform Energy Factor (UEF). Convert electricity using 3,412 Btu per kWh or natural gas using 100,000 Btu per therm, then apply the relevant national average price. These figures are estimates, not guaranteed household costs; your actual bill will depend on your rates and the specific water heater you choose.

Example unit	UEF	Estimated energy per year	Estimated cost per year
Heat pump, ENERGY STAR minimum	3.3	about 997 kWh	about $172
Heat pump, Rheem ProTerra 50 gal 30A	3.88	about 847 kWh	about $147
Gas tank, ENERGY STAR medium-draw minimum	0.81	about 138 therms	about $205
Gas tank, Rheem atmospheric 40 gal	0.66	about 170 therms	about $252

These estimates use national average energy prices and rated UEF values. Actual costs vary with local rates, climate, and usage. Fixed gas charges and installation costs are excluded. The federal Section 25C tax credit ended for property placed in service after December 31, 2025. Eligible households may qualify for HEAR rebates of up to $1,750 for ENERGY STAR heat pump water heaters where state programs are available. Compare why your gas bill is so high, then check whether your home needs wiring, drainage, or other changes to install a heat pump.

Switching From Gas to a Heat Pump Water Heater: Space, Wiring, Venting, and Recovery

Replacing a gas water heater with a heat pump model can change more than the energy source. Heat pump units need enough surrounding air, a condensate drain, and a suitable electrical circuit. A gas model, by contrast, needs the right gas connection and venting arrangement.

Space, temperature, and airflow

The Department of Energy recommends installing a heat pump water heater where temperatures stay between 40°F and 90°F year-round. ENERGY STAR guidance calls for about 1,000 cubic feet of air space around the unit, though installation requirements vary by model. Some installations need additional ventilation or ducting, especially in a closet. Check the manufacturer's instructions before choosing a location. A cramped space with little airflow can affect performance.

Electrical wiring and gas connections

Many full-size heat pump water heaters need a 240V circuit on a 30A breaker, though 120V models are available. Check the requirements for your chosen unit. Switching from gas may also involve changes to the old gas line and venting, which a licensed plumber should handle. An electrician can check your panel capacity, install the circuit, and assess backup power needs.

Condensate and hot water recovery

Heat pump water heaters need a condensate drain or, in some cases, a condensate pump. Check the model's First Hour Rating, too, to make sure it can meet your household's hot water demand. For example, the supplied Rheem specifications list 67 gallons per hour for a 50-gallon, 30A ProTerra model. If you want to store solar energy for household use or outages, explore solar battery systems and have an electrician confirm that the setup supports your water heater's electrical requirements.

Pros and Cons of Heat Pump and Gas Water Heaters, Plus Safety and Maintenance

Neither option suits every home. A heat pump water heater can reduce energy use, but it needs electricity, space, and a suitable drain. Gas models can be easier to install in homes already equipped for gas, and some can operate during an outage without any battery.

Heat pump water heater

Heat pump water heaters offer high efficiency without combustion, but they need suitable space, airflow, and electrical capacity. Consider these pros and cons before choosing one for your home.

Pros	Cons
ENERGY STAR integrated models rated UEF 3.30 or higher	Needs a 40°F to 90°F space (DOE) and air volume (ENERGY STAR)
No combustion or flue	Many full-size models need a 240V/30A circuit
Can help cool and dehumidify the space (ENERGY STAR)	Stops heating in an outage; element mode draws 4,500W on Rheem's 30A models
From 2029, the federal standard moves common-size electric tanks to heat pump efficiency (DOE)	Higher upfront cost; federal 25C credit ended after 2025 (IRS)

Gas water heater

Gas water heaters can suit homes with existing gas lines and venting, often keeping replacement costs simpler. However, efficiency, electrical needs, and combustion safety vary by model.

Pros	Cons
Atmospheric models need no electrical outlet (Rheem)	UEF below 1 (ENERGY STAR gas storage minimum 0.81; Rheem atmospheric example 0.66)
Simple replacement where gas and venting already exist	Needs venting, combustion air, and yearly service (CDC)
Lower energy price per unit of heat at 2025 national averages (EIA)	Power vent and tankless models need electricity (Rheem, Rinnai)
Strong first-hour ratings in the Rheem atmospheric series (52 to 105 gallons)	Combustion means CO alarms are a must (CPSC)

Safety and maintenance

Have a qualified technician service your water heater and other fuel-burning appliances every year, as the CDC recommends. The CPSC also advises installing carbon monoxide alarms on every level of your home and outside sleeping areas. If you keep a gas water heater, monitoring indoor carbon monoxide should be part of your household safety routine. Maintenance depends on the type of water heater. For a heat pump model, follow the manufacturer's instructions for cleaning or replacing filters and checking the condensate line. For a gas model, schedule annual service and keep the area around the burner and vent clear.

Conclusion

Heat pump water heaters can use less energy than gas models, but the best choice depends on your utility rates, installation requirements, hot water demand, and outage needs. Compare UEF ratings and EnergyGuide labels, then check whether your home has enough space, drainage, and electrical capacity for a heat pump. If you keep a gas water heater, confirm whether it needs electricity before buying backup power. EcoFlow TITAN Plus may suit a compatible heat pump circuit, while EcoFlow TITAN Classic is intended for compatible 120V loads such as certain gas water heater controls. Ask a licensed electrician to confirm the setup before relying on either system.

FAQs

Is a heat pump water heater cheaper to run than gas?

It can be. In the supplied example using 2025 national average energy prices, a heat pump model with a UEF of 3.30 costs about $172 a year to operate. The gas models shown range from about $205 to $252 under the same assumptions. Your local rates, model efficiency, and operating conditions can change the result.

Does a gas water heater work during a power outage?

Some do. A traditional atmospheric gas tank with a standing pilot may keep heating without electricity. Power-vent tanks and most tankless models need electricity for fans, ignition, or controls, so they generally stop during an outage unless those loads have compatible backup power.

Is a heat pump water heater more efficient than a gas water heater?

ENERGY STAR's supplied criteria list a minimum UEF of 3.30 for integrated heat pump water heaters, compared with 0.81 to 0.86 for gas storage models and 0.95 for gas tankless models. Compare the ratings for the specific products you're considering.

Can I replace a gas water heater with a heat pump model?

Often, yes, but the installation needs to meet the new unit's requirements for air space, temperature, drainage, and electrical supply. Many full-size models need a 240V circuit, although 120V options exist. Have a licensed plumber and electrician review the installation before buying.

Are gas water heaters being banned?

No. The DOE's 2024 rule raises efficiency requirements for covered water heaters, with compliance required on and after May 6, 2029. It doesn't prohibit gas water heaters. Check the applicable requirements for the model you're planning to install.