Backup Power Goals for Homes: What You Need to Run and Why It Matters

A residential backup power system exists to keep specific household functions running when the utility grid is unavailable. The goal is not “power the whole house” by default; the goal is to maintain safety, prevent property damage, preserve food/medicine, and sustain basic comfort for the type of outages you actually experience.

Start with outage scenarios and translate them into critical loads

Different outages create different risks. Begin by listing the scenarios that matter in your home, then map each scenario to the loads (circuits/appliances) that reduce the risk.

Scenario A: Short outage (minutes to a few hours)

• Primary risks: loss of lighting, loss of internet/communications, inability to open garage door, disruption to work/school, brief heating/cooling interruption.
• Typical critical loads: a few lighting circuits, refrigerator (optional for short duration), modem/router, phone charging, garage door opener, a few receptacle circuits for laptops.

Scenario B: Multi-day outage (1–7+ days)

• Primary risks: food spoilage, inability to cook, loss of water (well), loss of heat (even if you have gas/oil heat), inability to keep devices charged, fatigue from manual workarounds.
• Typical critical loads: refrigerator + freezer, heating system controls/blower (or boiler controls), well pump or water booster, kitchen receptacles for small appliances, networking, selected lighting, possibly a dehumidifier or sump pump depending on season.

Scenario C: Cold weather outage (freezing temperatures)

• Primary risks: frozen pipes, unsafe indoor temperatures, carbon monoxide risks from improvised heating, inability to run heat distribution fans/controls.
• Typical critical loads: furnace/boiler controls, circulation pumps, blower motor, thermostats, ignition systems, and possibly a small space heater only if your backup system can support it (space heaters are high-wattage).

Scenario D: Sump pump / flooding event

• Primary risks: basement flooding, mold, property damage.
• Typical critical loads: sump pump circuit (sometimes two pumps), dehumidifier (secondary), a few lights for safe access.

Write your scenarios as short statements you can test your plan against, such as: “If the power is out for 72 hours in January, we can keep the house above 60°F, keep pipes safe, keep food cold, and have water.”

Must-run vs nice-to-have: a structured decision method

Use a two-pass approach: first decide what is non-negotiable (must-run), then decide what is comfort (nice-to-have). This prevents oversizing and helps you choose the right type of solution.

Pass 1: Must-run (safety, health, property protection)

• Health: medical devices (CPAP, oxygen concentrator, refrigerated meds), essential charging.
• Property protection: sump pump, well pump (if needed to prevent freeze or maintain sanitation), heating controls to prevent frozen pipes.
• Food/medicine preservation: refrigerator, freezer.
• Basic communications: modem/router, a way to charge phones, possibly a small TV/radio for alerts.
• Minimum lighting: a few LED lighting circuits or plug-in lamps.

Pass 2: Nice-to-have (comfort, convenience, productivity)

• Comfort: additional rooms’ lighting, ceiling fans, more outlets, entertainment.
• Cooking convenience: microwave, toaster oven, coffee maker (often high draw but short duration).
• Work-from-home: office circuit, printer, extra monitors.
• Whole-house feel: central air conditioning or electric range (often pushes you toward larger systems).

Decision rules that keep you honest

• If a load prevents injury, illness, or major damage, it belongs in must-run.
• If you can substitute it easily (flashlights instead of whole-house lighting), it’s usually nice-to-have.
• If it is high-wattage resistive heat (space heaters, electric water heater, electric oven), treat it as a special case: include only with a deliberate plan and sufficient capacity.
• If it has a motor/compressor (well pump, fridge, sump pump), plan for higher starting power than running power.

Common critical loads and what “running it” really means

When you say “I need heat,” you may only need the controls and distribution powered. Many fuel-fired systems still require electricity for ignition, controls, and fans/pumps.

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Worksheet method: build your load plan step-by-step

The objective of the worksheet is to produce three numbers you can act on:

• Peak running watts (what you need continuously when multiple items are on)
• Starting surge allowance (extra capacity for motors/compressors starting)
• Energy per day (watt-hours/day) to estimate fuel needs and runtime

Step 1: Room-by-room inventory (10–20 minutes)

Walk through the home and list what you would want during an outage. Do it by room to avoid forgetting “hidden” loads.

• Kitchen: refrigerator, freezer (if separate), microwave, coffee maker, small appliances, a few lights.
• Mechanical room: furnace/boiler, circulator pumps, condensate pump, sump pump, well pump controls, any alarm panels.
• Bedrooms: CPAP/medical devices, phone chargers, one lamp.
• Office/living: modem/router/ONT, laptop, a lamp, TV (optional).
• Garage/outside: garage door opener, exterior light (optional).

Then tag each item as MUST or NICE.

Step 2: Identify how each item is powered (circuit vs plug)

For each item, mark whether it is:

• Plug load: can be powered by a receptacle (lamp, router, microwave).
• Hardwired/circuit load: typically on a dedicated circuit (furnace, well pump, sump pump).

This matters because plug loads are easier to manage flexibly, while circuit loads often define the minimum “infrastructure” your backup plan must support.

Step 3: Read nameplates and labels (capture real numbers)

Use the equipment nameplate, user manual, or a label near the motor/control box. Record what you find; don’t guess if you can avoid it.

• Watts (W): if listed, record directly.
• Amps (A) and volts (V): compute watts as W ≈ V × A.
• For 120 V plug loads: many labels show amps; example: 120 V × 2.5 A ≈ 300 W.
• For 240 V loads (common for well pumps): example: 240 V × 6 A ≈ 1440 W.

Also note if the label mentions LRA (locked-rotor amps) or starting current; that’s a clue the starting surge could be much higher than running.

Step 4: Add duty cycle assumptions (how often it runs)

Many critical loads do not run continuously. Estimating duty cycle helps you plan fuel and runtime realistically.

• Refrigerator/freezer: often cycles; use a conservative duty cycle like 30–50% depending on ambient temperature and door openings.
• Furnace blower/boiler pump: depends on weather and thermostat setpoint; in cold snaps it may run a large fraction of the hour.
• Well pump: short bursts; total daily runtime depends on water use and pressure tank size.
• Sump pump: can be near-zero most days or near-continuous during heavy rain; plan for a worst-case event if flooding is your key risk.
• Networking: typically continuous.

Write duty cycle as a percentage or minutes per hour. Example: Fridge: 40% (24 h/day), Well pump: 10 min/hour during active use.

Step 5: Set runtime targets (what “success” looks like)

Define how long you need to sustain must-run loads without resupply or major intervention.

• Short target: 4–8 hours (bridges most brief outages)
• Overnight target: 12–18 hours (sleep without worry)
• Multi-day target: 48–96+ hours (storm recovery)

Runtime targets should match your scenario list. If your area sees frequent 2–3 day outages, plan for that, not just “a few hours.”

Step 6: Calculate peak running watts and surge allowance

Create two totals: (1) what might run at the same time, and (2) what might start while other loads are running.

• Peak running watts: sum the running watts of loads you expect simultaneously (e.g., fridge + furnace blower + router + some lights).
• Surge allowance: add extra capacity for the largest motor starting event (often well pump or sump pump). If you don’t have starting data, assume motor loads may need several times their running watts briefly.

Practical scheduling can reduce required peak. Example: don’t run microwave while the well pump is likely to start; avoid running multiple high-draw kitchen appliances at once.

Step 7: Estimate daily energy (watt-hours/day)

Energy is what drives fuel use and battery sizing. For each load:

Daily Wh = Running W × Hours per day (or × 24 × duty cycle)

Example (illustrative numbers):

• Router/ONT: 20 W × 24 h = 480 Wh/day
• Fridge: 150 W × (24 h × 0.4) ≈ 1440 Wh/day
• LED lighting: 60 W × 5 h = 300 Wh/day

Add them up for must-run loads first; then see what nice-to-have items do to the total.

Fill-in worksheet template (copy and use)

Use this table as a working document. Start with must-run only.

Turn your worksheet into a practical load plan

Create a “critical loads list” you can follow during an outage

Once you’ve identified must-run loads, write a short operating plan that reduces peak demand and extends runtime:

• Always on: networking, essential lighting, medical devices.
• Cycle loads: refrigerator/freezer (keep doors closed; avoid frequent openings).
• One-at-a-time loads: microwave/coffee maker/toaster oven; avoid stacking with pump starts.
• Storm mode: if sump pump is active, postpone nonessential cooking appliances.

Define your “comfort level” in measurable terms

Comfort is easier to budget when you define it. Examples:

• “Maintain 60°F in living areas; bedrooms can be cooler.”
• “Keep internet up continuously for remote work.”
• “Cook one hot meal per day using a single appliance at a time.”

Choosing portable vs permanent standby: criteria you can apply

Use your worksheet outputs (must-run list, peak running watts, surge needs, daily energy, runtime targets) to decide which category fits your goals.

Choose a portable solution when these are true

• Comfort target is modest: you’re focusing on must-run loads and can live without whole-house convenience.
• Budget is limited: you want the most capability per dollar and can accept manual setup.
• Outages are occasional or short: you can respond when needed and don’t require seamless operation.
• Fuel access is flexible: you can obtain and store appropriate fuel, and you’re comfortable refueling during an outage window.
• Manual operation is acceptable: you can start the unit, manage loads, and monitor fuel.

Choose a permanent standby solution when these are true

• Automation is required: you need power to come on without anyone home (medical needs, travel, rental property, critical sump pump risk).
• Multi-day resilience is a priority: you want extended runtime with minimal hands-on intervention.
• Higher comfort target: you want more circuits supported simultaneously and less load juggling.
• Fuel availability supports it: you have a reliable long-duration fuel source and want fewer refueling trips.
• Lower tolerance for disruption: you want a system that behaves more like utility power for daily life continuity.

Quick decision checklist (answer yes/no)

• Do you need automatic operation when you’re away or asleep? If yes, lean permanent standby.
• Is sump pump or freeze protection a high-stakes risk? If yes, lean toward higher automation and reliability.
• Can you safely manage fuel and manual startup during storms? If no, lean permanent standby.
• Is your must-run list small and your runtime target short? If yes, portable is often sufficient.
• Do you want to power many circuits without scheduling? If yes, lean permanent standby.