A storage tank with a millivolt control needs no power
The water heater that keeps working in an outage is the natural-draft storage tank with a millivolt gas control. Bradford White's Canadian spec sheet for the RG240T6N lists the electrical supply as none required, because the control is powered by the pilot thermopile. With gas still flowing, the burner can run and the tank keeps delivering hot water.
That is a specific design, not a rule for every gas tank. A power-vent or direct-vent tank uses a blower and electronic controls that need electricity, so it stops like a tankless unit. Whether a given tank will work in an outage is read from its own spec sheet and control type, not assumed from the fact that it burns gas.
A condensing tankless unit stops without power
A condensing tankless unit has no stored hot water and needs electricity for the fan, the control board and the freeze protection. The Rinnai RU199iN runs on 120 V and draws 148 W when freeze protection is active against 84 W in normal operation. If the power fails, the unit stops and there is no hot water until power returns.
The freeze protection is another reason the unit needs power in winter. It protects the unit's internal water path, not the building's pipes, and it cannot run on a dead circuit. A vent or condensate line that freezes during a long outage is a separate risk the installation accounts for.
What FortisBC advises before an outage
FortisBC's outage guidance is to make a family emergency plan, post emergency and utility numbers, and prepare a kit with at least 72 hours of supplies. It also recommends carbon monoxide alarms where fuel-burning backup equipment such as generators, wood stoves or propane heaters may be used, and surge-protecting power bars for electronics.
Customers who depend on power for medical needs can register as a vulnerable customer with FortisBC. For a water heater, the practical preparation is knowing whether the unit needs electricity at all and where the gas shut-off is, without attempting any gas work.
During the outage
FortisBC advises switching off appliances, electronics and lights to prevent a surge when service is restored, while leaving one light on inside and one outside to show when power is back. It warns against touching the circuit breaker or fuse panel with wet hands or while standing on a damp floor.
On gas appliances, FortisBC states that a gas furnace will not operate during an outage but a gas fireplace can provide warmth until power returns. It does not direct homeowners to relight or service gas equipment, and this site publishes no instructions for gas, combustion or venting work; those are done by a licensed gas fitter.
When the power returns
FortisBC advises waiting 10 to 15 minutes after power is fully restored before slowly turning everything back on, to let the electrical system stabilise, and notes this matters especially in winter. A tankless unit that was off will restart on its own; if it does not fire or shows a fault code, that is a service call rather than something to work around.
A storage tank that ran through the outage needs no special action, but a unit that was already near the end of its life may reveal a problem when it cycles back on. A no-hot-water call after an outage is diagnosed first, and the diagnostic charge is credited toward the repair.
Planning for the next outage
Outage resilience is one of the few clear trade-offs between a storage tank and a tankless unit. A natural-draft tank with a millivolt control keeps working without power; a condensing tankless unit trades that for higher efficiency, wall space and continuous hot water while power is available. Neither is right for every home, and the choice is made from how the household uses hot water and how often the power goes out.
CANRO Heating & Cooling repairs and diagnoses gas water heaters across its verified Metro Vancouver coverage, and provides free written estimates for replacements. The diagnostic charge for a repair visit stays distinct from the free install or replacement estimate.