Battery Backup for Home: How Many Hours of 'Normal Life' Do You Need?
- What Should Your Home Battery Backup System Really Be Powering During A Power Outage?
- How to Calculate What Size Backup Battery for Home You Actually Need?
- What Can a 4 to 6 Hour Battery Backup for Home Power Outage Handle?
- How Long Will an 8 to 12 Hour Home Backup Battery Keep Things Running?
- What Does 24 Hour Battery Backup for Home Actually Look Like?
- Can You Really Run a Backup Battery for Home for 48 to 72 Hours?
- Should You Choose a Portable Power Station or Fixed Whole Home Battery Backup?
- Select Capacity
- Frequently Asked Questions
It’s not a question of how long you can, but how long you need. Most people’s perfect window of opportunity for a backup system will fall somewhere in the realm of 6 hours to 3 days, depending upon what you can’t do without and how often the lights go out. Let’s calculate your number.
What Should Your Home Battery Backup System Really Be Powering During A Power Outage?
Before you select the size of the batteries you will use, you must understand what you are going to leave on and what you are going to unplug. Not everything is worth having backup power, and you cannot run the entire house as if nothing is wrong because the largest system you have won’t last long.
The Stuff That Can’t Go Off
Your refrigerator leads the pack. A typical modern refrigerator is usually a “hundreds-of-watts when the compressor is running” kind of load, and it cycles on and off throughout the day. The exact number depends on the model, temperature settings, and room conditions, and it also has a brief startup surge. Let it go, and you’ll be throwing away hundreds of dollars of food.
And so too your phone chargers and Wi-Fi routers, which are often low-wattage devices (routers are commonly in the ~5–20W range depending on model) but enable you to stay in touch with the world.
A few LED light sets for security purposes round out the essentials, and these will add perhaps 20 to 60 watts, depending upon how many you choose to use.
What You Can Use Strategically
Cooking appliances are found within the middle area. A microwave, for example, draws 1,000 watts of power but operates for only a few minutes.
Electric kettle or portable induction cooker - same principle - high current draw for a short period of time.
Your well pump, if you have one, also belongs to this list. It surges to 1,200 watts when it turns on, but cycles off when your pressure tank is full.
Laptops, TVs, and fans are some of the things that fall into this category, too. You can use them, but not all at once and not all day long.
The Power Hogs to Skip
Central air conditioning is the major power suck in the house. A standard unit often lands in the multi-kilowatt range while running (commonly cited around ~3,000–5,000W for central AC, depending on size and efficiency), and this can drain many backup batteries in a couple of hours if you try to run it continuously.
Clothing dryers, always-on electric water heaters, and EV charging stations must also be included in “not during outages.”
Pumps for pools can wait. Dishwashers can wait. If it can heat, cool, and spin at incredibly high speeds, it can wait.
After you sort your gear into these categories, you can begin to think in terms of hours.
How to Calculate What Size Backup Battery for Home You Actually Need?
To determine your required capacity, you only need to calculate the wattage of your important devices, multiply it by time, then add 30% to it.
The Basic Formula
Find where the power rating is marked on each important gadget, add those up, and then multiply by how long you want to power each one. This will give you your watt-hours, which is how batteries are rated. For instance, your fridge might average around 200 watts over time (accounting for cycling). Your router and modem consume 30 watts, lighting consumes 40 watts, and you may like to power a laptop of 60 watts for a few hours. This means a total of 330 watts at a time. To power this load for 6 hours, you would therefore need a minimum of 1,980 watt-hours.
But batteries aren’t 100% efficient. The power inversion from DC from batteries to AC for your house is typically most efficient at certain loads; high-quality pure sine wave inverters are commonly rated around 90–95% efficiency (and real-world efficiency varies with load). And you don’t want to fully drain your lithium-ion batteries if you want them to last. So take your figure and increase it by 25% to 30%. The 1,980Wh requirement turns into a 2,500Wh battery.
Matching Duration to Capacity
Here's how the numbers typically shake out:
| Target Runtime | Minimum Capacity | What It Supports |
| 4 to 6 hours | 1,000 to 2,000Wh | Fridge, lights, phones, one meal cooked |
| 8 to 12 hours | 2,000 to 4,000Wh | Overnight essentials, morning routine |
| 24 hours | 5,000 to 8,000Wh | Full day with careful load management |
| 48 to 72 hours | 10,000Wh and up | Multi-day independence, requires solar charging |
These aren't hard rules. A household that keeps things minimal can stretch a 3,000Wh portable power station for 24 hours. A family running multiple devices simultaneously might burn 8,000Wh before dinner.
What Can a 4 to 6 Hour Battery Backup for Home Power Outage Handle?
This is your ride-out-the-storm window. In many areas, a lot of everyday outages are resolved within a few hours—but major weather events can push outages much longer, so it’s safer to plan for more than the “typical” case.
You will be able to keep the fridge cool, charge your gadgets, light up the room, and perhaps cook one hot meal using the microwave or electric kettle. You will, however, not be able to cool the house using the air conditioner, have long hot showers, or act as if it were a normal day.
The usual 1,500Wh portable power station with an average of 1,200-1,500 watts of power will be able to handle this fine. It will be able to power your refrigerator’s ~200W average consumption for a period of 6 hours after considering the inefficiency of the power station, leaving some power for the lighting and small appliances.
How Long Will an 8 to 12 Hour Home Backup Battery Keep Things Running?
But now you’re covering overnight and into the next morning, which is important in case power outages in your area continue past sunset. This length of time will allow you to have a normal sleeping pattern, have your coffee, and have a semi-normal routine until noon.
With capacities of 2,000Wh to 4,000Wh, you can power the same necessities as the smaller window and then some strategic comfort loads. A space heater for an hour before bedtime. Enough laptop time to work from home. A hot breakfast.
The key is to stagger the draws. Do not heat lunch while the coffee is brewing and another person is powering a tool. Pick one high-draw appliance to run at a time and let the battery rest between the two. Most good home power backup units in the price range have a continuous power output of 2,000 to 3,000 watts.
What Does 24 Hour Battery Backup for Home Actually Look Like?
A whole day of backup power will see you through most weather-related outages without needing a generator. This is 5,000-8,000Wh of storage and is more expensive, but certainly gives you peace of mind if you live in an area of unreliable infrastructure.
In this capacity, you can support cooking three meals, operating the refrigerator, working with home appliances, and providing sufficient lighting to function. Some people even use the window unit air conditioner for a couple of hours in the middle of the day, but the capacity is quickly depleted.
The trick is to budget your day in tiers. Things that run constantly, like your fridge and router, are always on. Things that run on a schedule, like cooking and hot water, run at their scheduled times. Then there's discretionary stuff, like TV or gaming, that gets what's left. It's like rationing, but for electrons.
For this purpose, you will require a whole-house battery backup solution with a minimum power output of 3,000-5,000 watts. Most solutions within this category will allow you to add additional batteries, which means you could start with a 5,000Wh solution and work your way up to 8,000Wh or higher.
If you want a concrete “whole-home direction” example (especially when 120V/240V matters), EcoFlow’s DELTA PRO ULTRA X is built for split-phase whole-home use and modular expansion—so instead of running extension cords to rooms, you’re thinking in circuits and priority loads.
Can You Really Run a Backup Battery for Home for 48 to 72 Hours?
Yes, but that takes planning and usually involves solar panels. A 10,000-15,000 Wh battery bank can power a subsistence level of electricity for 3 days, provided you are very ruthless in power conservation and can recharge during daylight hours. That’s hurricane-level preparedness. You’re rotating all the loads, cooking once a day, forgoing showers, and conserving electricity like it’s the precious commodity it is. It’s not comfortable, but it’s doable without wasting gas in a generator.
Most people setting up multi-day backups involve multiple portable power stations or have a home modular battery backup system that takes solar power. A couple of hundred watts of solar power can add on the order of ~1,000-2,000Wh on a good sunny day, depending on sun hours and system efficiency, and thus provide an indefinite power supply.
This is also where modular systems like DELTA PRO ULTRA X are easiest to justify: multi-day outages are less about “one big battery” and more about scalable storage + meaningful solar input, so you can keep essentials running and recharge during daylight rather than counting down to zero.
Should You Choose a Portable Power Station or Fixed Whole Home Battery Backup?
Each has its advantages, and it is up to you to choose what suits your budget, convenience, and special needs, if any, such as medical equipment.
Portable Units
Portable units excel in terms of flexibility and cost. A 2,000Wh portable power station will cost you anywhere from the high hundreds to the low thousands of dollars, depending on output power, feature set, and seasonal promos. Installation only takes minutes, and you could move it with you to camp with when the power is good. It allows you to begin with one and then add additional ones in the future to create your home backup power solution.
Fixed Installations
They are convenient. They reside in your garage, are connected to your electric panel, and often switch on automatically when paired with an automatic transfer setup when the power goes out. However, the installation costs $5,000 to $15,000, and they are fixed, which means you can’t relocate them, and installation is done by a professional.
Unless you have some medical requirements that would necessitate an instant automatic backup solution, for most people, a portable power station would be a more practical option because you get 80% of what you want at 20% of the cost.
Check for the presence of a pure sine wave output to shield your electronics, the availability of solar charging, and sufficient AC ports to connect your crucial devices. The presence of pass-through charging, which enables you to use the power bank while it is charging, is an additional feature. The UPS feature for sensitive devices such as computers is also an advantage.
Select Capacity
Add up the watts, multiply it by the desired hours, and then tack on 30%. That's the minimum capacity. And then you have to determine if you're preparing for 4-hour nuisances or 48-hour disasters.
Frequently Asked Questions
Q1. Should I Size My Backup for Just 4 Hours?
No, go bigger. The averages don’t show you the tail. The average outages could be 2 or 3 hours, but it is the occasional 12-hour winter storm power outage that you need to prepare for. If your average is 4 hours, you need 8-12 hours. You will need it only once or twice a year and be thankful you have it. Additionally, deep discharging your batteries reduces their life. So, actually increasing your home backup system size by 50% can help you avoid frequent deep discharges, which is generally better for long-term battery health.
Q2. Can a Battery Backup Run a Well Pump?
Most 1/2 to 3/4 horsepower well pumps consume 800 to 1,200 watts, but surge 2,000 to 3,500 watts for a brief moment during startup. Be sure to check your battery’s surge capacity, not just its continuous rating. A battery rated for 2,000 watts continuous might surge 4,000 watts for a brief moment, which is sufficient for most pumps during startup. However, you will quickly deplete your battery’s capacity if you’re refilling a large pressure tank. The pump will consume a meaningful chunk of energy depending on the pump’s wattage and how long it runs, and you don’t want to run water too much during power outages.
Q3. Is It Ok to Keep a Home Battery Plugged in All the Time?
Trickle charging draws a small amount of power (often single-digit to low-teens watts, depending on the system), so the annual electricity cost is usually modest. Modern lithium batteries will be happy if you keep them topped up and do not let them sit discharged. Most good portable power stations come with battery management circuits that will not let the battery be overcharged. The problem of battery longevity is not the charge cycles; it’s the temperature. Store your emergency power source in a temperature-controlled environment, and not in a garage or a cold shed. If stored under optimal conditions and maintained charged, the battery will last you for many years, and many LFP-based systems are commonly rated for thousands of cycles until you notice a degradation in capacity.
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