The 72-Hour Home Outage Sizing Guide: How Much Backup Power Do You Actually Need?

Most homeowners who buy backup power get it wrong in one of two directions. They either buy a 500Wh station that can charge phones but can't keep a refrigerator running — or they price out a whole-home battery system, stagger at the $15,000 quote, and buy nothing at all.

There is a rational middle path, and it starts with a single question: what do you actually need to run, and for how long?

The answer most emergency preparedness experts settle on is 72 hours. That is the threshold FEMA's Ready.gov program uses for household emergency kits, and it maps reasonably well to how most grid outages resolve. Utility crews are typically on-site within 72 hours after severe weather events. Planning for that window — with a strategy to extend it using solar recharging — gives most homeowners a durable, practical backup solution at a fraction of the cost of a whole-home installation.

This guide walks you through the math, step by step.

Why 72 Hours Is the Right Planning Horizon

Short outages — a few hours after a thunderstorm — are inconveniences. Your refrigerator holds temperature for about four hours with the door closed. Your phone holds charge. You light candles and wait.

The outages that cause real damage are the ones that last longer: ice storms, hurricanes, extreme heat events, and wildfires. These routinely knock out power for one to four days, sometimes longer in rural areas. A 72-hour planning horizon covers the vast majority of these events while keeping your equipment budget in a range most homeowners can actually manage.

Beyond 72 hours, you are in a different planning category — one that typically involves either a whole-home battery system, a generator, or a portable power station paired with enough solar panels to sustain you through extended runs. We will touch on the solar pairing strategy at the end of this guide, because it is genuinely powerful and often overlooked.

Step 1: Separate Essentials from Luxuries

The biggest mistake in outage planning is trying to power everything. You do not need to power everything. You need to power the things that matter.

Divide your household into three tiers:

Tier 1 — Non-negotiable (life and safety)

• Sump pump (if you have a basement)
• Medical devices: CPAP, oxygen concentrator, insulin refrigeration, home dialysis
• Smoke and CO detectors (battery-powered, but good to verify)

Tier 2 — High value (food and communication)

• Refrigerator
• Chest freezer (if you have one)
• Router and modem
• Laptop and phone charging

Tier 3 — Comfort (worth including if budget allows)

• Lighting (LED is very efficient)
• Fans (much more power-efficient than air conditioning)
• Small window AC unit in extreme heat situations

Skip during an outage: Central air conditioning, electric range or oven, electric water heater, dishwasher, clothes dryer, and EV charging. These are high-draw appliances that dramatically change your storage requirements without adding much to your immediate safety or food preservation.

Step 2: Calculate Your 24-Hour Essential Load

Every appliance has a wattage rating (usually on a label near the power cord or in the manual). Multiply running watts by daily runtime hours to get watt-hours (Wh), which is the currency of battery capacity.

Here are typical consumption figures for common essentials:

| Appliance | Running Watts | Hours/Day | Daily Wh |

|---|---|---|---|

| Modern refrigerator | 100–200W | ~8–10 (cycles) | 800–2,000 |

| Chest freezer | 80–150W | ~8–10 (cycles) | 640–1,500 |

| Router + modem | 15–25W | 24 | 360–600 |

| LED lighting (4 fixtures) | 30–50W | 8 | 240–400 |

| Phone charging (2 phones) | 20–40W | 4 | 80–160 |

| Laptop | 45–65W | 6 | 270–390 |

| Box fan | 50–75W | 12 | 600–900 |

| CPAP (no heated humidifier) | 30–60W | 8 | 240–480 |

| Sump pump | 400–800W | 1–2 | 400–1,600 |

Note that refrigerators and freezers do not run continuously — the compressor cycles on and off. A modern Energy Star refrigerator typically draws full power for only 8–10 hours out of every 24. This is why the "200W × 24h = 4,800Wh" estimate many people use is too high by nearly half.

Example household calculation:

For a typical 3-bedroom home with a refrigerator, router, lighting, two phones, a laptop, and a fan:

• Refrigerator: 1,200Wh
• Router: 480Wh
• Lighting: 320Wh
• Phones: 120Wh
• Laptop: 330Wh
• Fan: 750Wh

Total: ~3,200Wh per day

Add a sump pump or CPAP and that climbs to roughly 3,600–4,500Wh per day.

Add a 15% buffer to account for inverter efficiency losses: ~3,700–5,200Wh per day is the realistic planning range for an active household running essentials.

For 72 hours of storage with zero recharging, you would need 11,100–15,600Wh — that is a whole-home battery category, not a portable power station. This is why the recharging strategy matters so much, which we cover below.

Step 3: Match Your Load to an EcoFlow Model

EcoFlow makes several portable power stations designed for home backup. Here is how they map to the household loads above:

EcoFlow DELTA 2 (~1,024Wh)

Best for: Apartments, very light loads, or supplementing a larger setup. Covers approximately 6–12 hours of a minimal essential load (router, lighting, phone charging, laptop only — no refrigerator). Not the right primary station for a family home during a multi-day outage, but a solid second unit or starter.

EcoFlow DELTA 2 Max (~2,048Wh)

Best for: 1–2 person households with light essential loads, or as a primary station in climates where outages rarely last more than 24 hours. Covers approximately 12–18 hours of the household example above. With a solar panel charging during daylight hours, it can sustain a light load indefinitely in good weather.

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EcoFlow DELTA Pro Ultra

For homeowners who want seamless whole-home backup across most circuits, automatic switchover, and capacity that can grow to 21.6kWh. This is a semi-permanent installation rather than a portable unit, and it occupies a different category and price point. Worth a look if you are also planning a solar installation — it integrates directly with a home solar array.

The Solar Multiplier: Why You Should Think Beyond the Battery

Here is the insight that changes the math considerably: you do not need 72 hours of storage if you can recharge during those 72 hours.

Two EcoFlow 220W bifacial solar panels produce approximately 1,200–1,800Wh on a decent sun day, depending on your location and roof or ground orientation. If your essential household load is ~3,500Wh per day, solar panels cover roughly 35–50% of that — meaning a fully charged DELTA Pro effectively stretches its runtime from 24 hours to 36–48 hours, even with modest summer sun.

More importantly: in a typical 3-day storm outage, at least one of those days usually has workable sun. A single day of good solar input to a DELTA Pro adds back 1,200–1,800Wh — that is 6–10 more hours of essential power without any additional battery capacity.

EcoFlow 220W Portable Solar Panels fold flat for storage and set up in minutes. They are also the same panels you would use to start experimenting with solar energy before committing to a full rooftop installation — a real benefit if you are actively researching residential solar.

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The combination we recommend for most 3–4 bedroom homes: DELTA Pro + two 220W panels. Budget-conscious? Start with the DELTA 2 Max + one 220W panel, which covers a smaller household through a 72-hour event with one sunny day in the mix.

EcoFlow vs. a Gas Generator: Running the Numbers

Gas generators are still the most common home backup solution, and they have one undeniable advantage: unlimited runtime as long as you can get fuel. But the cost comparison is closer than most people expect, and the trade-offs are real.

A quality dual-fuel generator in the 3,500–7,500W range costs $500–$1,500 upfront. Add to that:

• Fuel: A 5,500W generator burns roughly 0.6–0.8 gallons per hour at 50% load. A 72-hour outage at 12 hours/day of runtime uses 25–35 gallons — roughly $90–$130 at current prices, assuming you can find fuel after a major storm (not always guaranteed).
• Maintenance: Annual oil changes, carburetor cleaning, fuel stabilizer, and a new spark plug — roughly $50–$100/year whether you use it or not.
• Carbon monoxide risk: Generators must run outdoors and cannot be operated in an attached garage. Setup and extension cords become a meaningful friction point.
• Noise: Most portable generators run at 65–75 decibels. An EcoFlow DELTA Pro operates silently.

Over five years, a generator's total cost of ownership often exceeds its purchase price. The EcoFlow DELTA Pro carries no fuel cost, requires no maintenance, can be used indoors, and charges from the wall when grid power returns or from solar panels when it doesn't. The premium over a mid-range generator is real — but so is the value.

How This Connects to Your Solar Plans

If you are researching residential solar on a site called SolarSimple, you already know the core challenge: rooftop solar does not provide backup power on its own. Grid-tied systems shut down during outages to protect utility workers. Battery storage is what bridges that gap — and whole-home battery systems (Powerwall, Enphase IQ, Franklin WH) run $10,000–$20,000 installed.

A portable power station like the EcoFlow DELTA Pro is not a replacement for that long-term investment. But it does several useful things in the meantime:

It gives you backup power now, while you are still in the solar research and installation pipeline (which typically takes 4–12 months from first quote to system turn-on).

It gives you real consumption data. Running your DELTA Pro through a few outage scenarios — or even just through a weekend as a test — tells you exactly how much power your household uses on essentials. That data is directly useful when sizing a future solar + battery system. Most installers ask you to estimate this; you will have actual measurements.

It becomes a complement, not redundant. After your solar installation, a DELTA Pro serves as portable backup for camping, power tools, outdoor events, and RV use — it does not get retired, it changes roles.

Our Recommendation by Household Type

Apartment or 1–2 person home, light load: EcoFlow DELTA 2 Max. Covers essentials through a typical outage, charges from a wall outlet overnight, pairs with one solar panel for extended coverage.

3–4 bedroom home, active household: EcoFlow DELTA Pro. The right size for the essentials load of a family home, expandable if needed, and accepts meaningful solar input to extend runtime across multi-day events.

Home with sump pump, medical equipment, or hurricane zone: EcoFlow DELTA Pro + two 220W solar panels. The solar pairing is not optional here — you need the daily recharge buffer to reliably cover a 72-hour outage scenario.

Large home or want automatic whole-home coverage: EcoFlow DELTA Pro Ultra, installed with the Smart Home Panel 2. Different category, different budget conversation — but worth a separate look.

Whatever size you choose, a fully charged station in your garage on the first day of a storm is worth more than a perfectly sized system that hasn't been delivered yet. Buy sooner, buy appropriately for your load, and add solar panels when the budget allows.

Last updated: 2026-06-19

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