The verdict, in one paragraph
Do the free things first, because they work with no power at all: let a faucet trickle on the most exposed run, open the cabinet doors under sinks on exterior walls, and if you are leaving, keep the thermostat no lower than 55°F. Then deal with the electrical half: a self-regulating heat cable on exposed pipe is the standard preventive measure, and in an outage it needs something to run it. The highest-value backup power in a winter storm is not heat — it is a gas furnace blower, which this site puts at about 800W running with an 800 to 1,600W start, well inside a 2kWh battery with a 1,800W or larger inverter. A house that keeps its heat never gets near the threshold where any of this matters.
Which pipes freeze, and in what order
Not all plumbing is at equal risk. The Red Cross identifies the vulnerable runs as:
- Exposed outdoor lines — hose bibs, swimming pool supply lines, sprinkler lines.
- Pipes in unheated interior areas — basements, crawl spaces, attics, garages and kitchen cabinets.
- Pipes running against poorly insulated exterior walls.
One useful technical point from the National Weather Service: wind chill does not affect pipes, because an object cannot cool below the actual air temperature. A 20°F air temperature means a 20°F pipe eventually, and a "feels like 5°F" forecast does not make that happen faster in any way that changes your plan. Air temperature and duration are the numbers that matter.
The free steps, in the order to do them
- Let a faucet trickle. Moving water through a pipe, even slowly, helps keep it from freezing. The NWS suggests running the faucet on an outside wall overnight. Pick the run furthest from where the water enters the house.
- Open cabinet doors under sinks on exterior walls, so warmer room air reaches the plumbing. Move household chemicals out of reach first if there are children or pets.
- Hold one steady temperature day and night. The Red Cross notes this may raise a heating bill but can prevent a far costlier repair. Do not set back overnight during a cold snap.
- If you are leaving, set the thermostat no lower than 55°F. Both the Red Cross and the NWS publish that figure for extended absences.
- Close the house up. Garage doors shut, crawl-space vents closed, and interior doors open so heat circulates.
None of that needs electricity, and in a short outage it is usually enough on its own.
Where backup power actually earns its place
The instinct in a cold outage is to buy heat. It is the wrong instinct, because electric heat is enormously expensive in watts and a battery is measured in watt-hours. The right targets, in order:
| What to power | Typical draw | Why it is worth the watt-hours |
|---|
| Gas furnace blower | About 800 W running; 800-1,600 W start | Keeps the whole house above the threshold. By far the best return per watt-hour. |
|---|
| Self-regulating heat cable | Varies with pipe temperature by design | Protects the one run that is genuinely exposed, at a small continuous draw |
|---|
| Router and modem | 20-40 W | Makes a temperature alarm work. Cheapest item on the list. |
|---|
| Boiler circulator pump | Small, varies by system | Same logic as a furnace blower on a hydronic system |
|---|
| Space heater | 750-1,500 W, published, with no starting surge | Poor value - heats one room and empties a battery in about an hour |
|---|
| Electric furnace or strip heat | Thousands of watts | Not realistic on battery. Shed it and protect the pipes directly. |
|---|
Furnace blower and space heater figures are this site's working averages, derived on the per-appliance pages linked below from Champion's published wattage chart. Heat cable draw varies by design, which is the point of self-regulating cable.
The furnace is the whole game
A gas or propane furnace burns fuel to make heat and uses electricity only to move air and run its controls. Lose the power and a house full of usable heating fuel sits idle because a blower will not turn.
That is the single highest-leverage use of a battery in a winter outage. At about 800W running, a 2kWh unit delivering roughly 1,760Wh covers a blower cycling through a night with room for a heat cable and a router — and a heated house does not have a pipe problem. Backup power for a furnace covers how to actually connect it, which is the part people skip.
If the heat is electric, this does not apply and the honest answer changes — backup power for a home with electric heat is the harder case, and protecting the pipes directly becomes the strategy rather than heating the house.
If a pipe does freeze
- Keep the faucet open. As the ice melts, water needs somewhere to go, and flow through the pipe helps the thaw along.
- Never use an open flame. The NWS recommends a hair dryer instead. Blowtorches start house fires and are the classic way this goes badly.
- Work from the faucet back toward the frozen section, so meltwater can escape.
- Know where the main shutoff is before you need it. If a pipe has already burst, that valve is the only thing that limits the damage.
What to buy, in order of value
- Nothing, if your outages are short and your heat is gas. The free steps cover a few hours comfortably.
- A heat cable for the one exposed run you already worry about. Fit it in autumn.
- A temperature alarm if there is a crawl space, a basement or a property you are not always in.
- A 1 to 2kWh battery sized to the furnace blower, with at least 1,800W of inverter to clear its start.
- A way to connect it to the furnace. The battery is useless if the furnace is hardwired and nothing bridges the gap.
The winter storm outage kit covers the non-electrical half, and staying warm without power covers keeping people comfortable while the house cools.
The short version
Trickle a faucet, open the cabinets, hold a steady temperature and do not set back below 55°F if you leave — those are free and they work without power. Put a self-regulating heat cable on the genuinely exposed run before winter starts. Then spend your backup-power budget on the gas furnace blower rather than on heat, because at about 800W it is the cheapest way to keep an entire house above the threshold, and a warm house never has this problem. Keep the battery indoors so it can still be charged in a cold snap, and find your main shutoff valve today.
