Lauren HollandBy Lauren Holland

Updated November 2026

Home backup power systems keep your essential loads running when the grid goes down. In this guide, you will learn how to list the appliances that matter most, calculate the watt-hours you need for a multi-hour outage, choose between a portable power station and a larger installed setup, and avoid the sizing mistakes that leave people in the dark after the first night.

What Home Backup Power Systems Actually Do

A backup system stores electricity, usually in lithium batteries, and feeds it to selected circuits or devices when utility power drops. Most homeowners do not need to power the whole house. Instead, they protect a short list of loads: a refrigerator, a few lights, phone and laptop charging, a medical device, and perhaps a sump pump. Sizing starts with that list, not with the size of the unit on a store shelf.

Shopping for one? See our guide: Top 5 EcoFlow Power Stations with Solar Panel Options for Home Backup (2026).

Portable options are often plugged into outlets or a transfer switch and suit apartments, rentals and modest homes. Larger installed systems tie into the electrical panel and can cover more circuits automatically. Our overview of Home Backup With a Solar Generator: What It Can Power and How to Connect Safely explains the connection options in more detail.

Step 1: Build an Essential Loads List

Walk through your home and write down every device you would want running during an outage. Then note its rated wattage, which is usually printed on a label near the power cord or on the back of the unit. Starting wattage matters for motors and compressors, which can draw a surge several times their running draw for a moment.

  • Refrigerator or chest freezer
  • Lights (LED bulbs, typically 5 to 15 watts each)
  • Wi-Fi router and modem
  • Phone, tablet and laptop chargers
  • CPAP machine (commonly 30 to 90 watts while running, depending on model and humidifier use)
  • Sump pump (often 800 to 1,200 watts running, with a higher start surge)
  • Window fan or small space heater, if you plan for them

Be cautious with high-draw appliances such as electric ranges, clothes dryers and central air conditioning. These usually fall outside what a portable system can run for long periods. If you need them, a whole-home or large-capacity installed system is the right conversation to have, and a licensed electrician should confirm the wiring.

Step 2: Calculate Your Daily Watt-Hour Needs

Watt-hours (Wh) measure how much energy a battery holds. To estimate what a device uses, multiply its wattage by the hours it runs per day. A 60-watt CPAP running 8 hours uses about 480 Wh per night. A refrigerator that cycles on and off may average 100 to 150 watts over 24 hours, which is roughly 2,400 to 3,600 Wh per day, but actual figures vary widely by model and temperature.

Refrigerators are the largest question mark. Check the appliance’s energy guide label, which lists annual kilowatt-hours. Divide that number by 365 to get an approximate daily kWh figure, then convert to Wh by multiplying by 1,000.

A Simple Sizing Example

Load Watts Hours per day Daily Wh
Refrigerator (average) 120 24 (cycling) about 2,880
CPAP with humidifier 60 8 480
LED lights (5 bulbs) 50 5 250
Phone and laptop charging 80 3 240
Wi-Fi router 12 24 288
Total about 4,140 Wh/day

Real systems lose some energy in conversion from battery DC to household AC, commonly 10 to 20 percent. Divide your total by roughly 0.85 to account for that loss. In this example, 4,140 Wh becomes about 4,870 Wh, so you would want a battery capacity near 5 kWh for one day of coverage with these loads, or more for multiple days.

Add Margin for Real Conditions

Batteries also should not be drained to zero routinely, and cold weather reduces usable capacity. Many people size for 20 to 30 percent more than their calculation to allow for those effects and for unplanned loads like a phone charged twice.

Step 3: Decide on Solar Recharging

Without a way to recharge, a battery covers one outage and then it is empty. Solar panels extend runtime for multi-day events. A rough check is to compare your daily Wh need to the panel wattage multiplied by about 4 to 5 peak sun hours in an average location. A 400-watt panel array might produce roughly 1,600 to 2,000 Wh on a good day, which can offset a modest daily load. Winter, shade and cloud cover all reduce output, so treat these numbers as estimates.

Solar options vary by product line. Some owners pair a portable station with folding panels, while others choose a bundled kit. Our comparison of 5 Best Solar Generators for Home Backup Power Picks Compared (2026) shows how different bundles approach this.

Step 4: Choose Your Connection Method

How the system connects to your home matters as much as its capacity. Options include:

  1. Direct plug-in: Power a fridge, router or CPAP through the unit’s outlets. Simplest and cheapest to set up, but every device needs its own plug.
  2. Interlock kit or dedicated circuit: A licensed electrician installs a transfer switch or a backup-circuit panel so selected circuits run automatically.
  3. Whole-home integration: A professionally installed system that backs up a large share of the panel, usually with automatic switchover.

Never backfeed a home through a standard wall outlet. That practice can energize utility lines and endanger line workers. Use a properly rated transfer switch or interlock installed to code. If you are unsure, consult a licensed electrician.

Step 5: Plan for Sump Pumps and Medical Devices

Sump pumps and medical devices deserve extra planning. A sump pump may need a surge capacity well above its running wattage, so check the unit’s startup rating before you buy. Run a test: switch the pump on with the backup system connected and confirm it starts and keeps up with inflow.

For CPAP users, verify the machine’s actual draw on the label and consider a spare battery or a plan for relocating to a shelter if an outage lasts beyond your capacity. Medical equipment questions should go to your physician or equipment supplier.

Common Mistakes to Avoid

  • Sizing only by the battery capacity printed on the box, without converting for inverter losses.
  • Forgetting startup surge for motors, compressors and pumps.
  • Running space heaters or dryers and assuming the system can keep up.
  • Skipping a test run. Try your setup on a normal day before you need it.
  • Letting the battery sit empty or fully discharged in storage. Follow the manufacturer’s charging guidance.
  • Improvised wiring or backfeeding. Use a transfer switch or interlock installed by a qualified electrician.

Tips for a Reliable Setup

  • Keep a written list of what the system powers and how long it lasts, and post it near the unit.
  • Recharge the battery to high levels whenever a storm is forecast.
  • Check the fridge door seals and keep it closed to stretch runtime.
  • Store the system somewhere dry, ventilated and above flood level.

These items help most people put a backup plan into practice. Check that any product you consider has the capacity, ports and certifications your plan requires.

  • Portable power station: The core of most small home setups, sized in watt-hours and offering both AC outlets and USB ports for charging. View on Amazon
  • Folding solar panels: Recharge the station between sunny days during longer outages, provided the panels match your station’s input limits. View on Amazon
  • Plug-in watt meter: Measures the real draw of your fridge, CPAP or router so your calculations use actual numbers. View on Amazon
  • Heavy-duty extension cords rated for outdoor use: Useful for connecting a station to a fridge in another room, but keep runs short and avoid daisy-chaining power strips. View on Amazon

FAQ

How many watt-hours do I need for a home backup power system?

Add up the daily watt-hours of your essential loads, add about 15 to 20 percent for inverter losses, then add a safety margin. A refrigerator, CPAP and lights often total several kilowatt-hours per day.

Can a portable power station run my whole house?

Usually not. Portable units are best for selected loads such as a fridge, lights, medical devices and charging. Whole-house coverage generally requires a larger installed system.

How long will a backup system run my refrigerator?

It depends on battery capacity and the fridge’s average consumption. Divide the battery’s usable watt-hours by the fridge’s average daily watt-hours to estimate days of coverage, then check the result against real use.

Do I need solar panels for a home backup power system?

Not for short outages. Solar becomes important for outages lasting more than a day or two, because it lets you recharge the battery.

Is it safe to plug a backup system into a wall outlet to power the house?

No. Backfeeding through a standard outlet can endanger utility workers and damage equipment. Use a transfer switch or interlock installed by a licensed electrician.

Can a sump pump run on a portable power station?

Many can, but check the pump’s starting surge and confirm the station can supply it. Test the setup before a storm.

How do I keep my home backup power system ready?

Charge it regularly, follow the manufacturer’s storage guidance, test it periodically under load, and review your essential loads list whenever you add or change appliances.

Conclusion

A good home backup plan starts with a clear list of essential loads and an honest watt-hour calculation. Choose a capacity with margin, decide whether solar recharging is worth adding, and connect the system safely through a proper transfer method. Test it before you need it, and consult a licensed electrician for any permanent installation.

Ready to choose one?

Lauren Holland

About Lauren Holland

Lauren Holland is part of our editorial team and reviews and edits our solar generators for home backup & emergencies guides, checking product details against manufacturer specifications and owner feedback.