“Will it run my whole house?” is the question we hear most about home backup power. The honest answer depends less on the brand and more on two numbers: how much energy your backup stores, and how much power it can deliver at once.
This guide explains the difference between whole-home and partial backup, what actually limits each one, and how Texas homeowners can get the coverage they want from a home battery, an EV with vehicle-to-home, or a standby generator.
The two numbers that decide everything
Storage (kWh)
The size of the tank. It decides how long your backup lasts. A bigger battery, or an EV with a large pack, runs the house longer.
Output (kW)
The size of the pipe. It decides how much can run at the same time. Go over it and the system shuts down to protect itself.
Startup surge
Motors like an AC compressor pull a short burst of extra power when they start. Your backup has to handle that burst, not just the running load.
Most people focus on storage, but output is what decides whole-home vs partial backup. A system can hold days of energy and still trip if the AC, the dryer and the oven all start at once.
What your home actually draws
These are typical running loads. Your own appliances will vary, which is why we size from your panel and your real usage.
| Appliance | Typical running load | Notes |
|---|---|---|
| Fridge and freezer | 0.1–0.3 kW | Cycles on and off |
| Lights, Wi-Fi, TVs, phone charging | 0.2–0.5 kW | Small, but always on |
| Microwave | 1–1.5 kW | Short bursts |
| Pool pump | 1–2 kW | Easy to pause in an outage |
| Central AC, per unit | 3–5 kW | Several times that for a moment at startup |
| Electric oven or range | 2–5 kW | Depends on burners in use |
| Electric water heater | 4–5 kW | Runs in long cycles |
| Electric dryer | 5 kW | One of the biggest loads in the house |
| EV charger | 7–11 kW | Usually paused during an outage |
Add it up and the problem is clear. A Texas home with two AC units, the dryer running and dinner in the oven can draw 15 to 20 kW, which is more than most single batteries or vehicle-to-home systems deliver. The same home with one AC unit and everyday loads draws well under 10 kW.
Whole-home backup
With whole-home backup, the battery or vehicle connects to your entire main panel. Every circuit in the house stays available during an outage, and you choose what to use in the moment.
- Nothing in the house goes dark, and nothing has to be rewired into a separate panel
- You decide in the moment whether to run the dryer or the AC
- Works well with load management that pauses big loads automatically
The catch is the output limit. If everything starts at once and the total goes past what the system can deliver, it overloads and shuts off until the load drops. Whole-home backup works best when the system is sized for your biggest loads, or when you’re comfortable running big appliances one at a time.
Partial backup
With partial backup, we move your essential circuits into a separate backup panel, often called a critical loads panel. Only those circuits run during an outage.
- The backed-up circuits can never add up to more than the system can carry
- Works with a smaller system and costs less to set up
- Nothing to think about in an outage: what’s backed up just works
The trade-off is that you choose ahead of time. Typical essentials are the fridge and freezer, lights, Wi-Fi, outlets, the garage door, fans and often one AC unit. Large loads like the dryer, oven, water heater and pool equipment usually stay off the backup panel.
A quick example
Take a home with two 4 kW AC units and a backup system that delivers about 11 kW. On whole-home backup, both AC units plus the fridge and lights fit, but starting the dryer on top of that would push it over. On partial backup, we’d put one AC unit and the essentials on the backup panel, so the system can never overload, and the second AC unit stays off until the grid comes back.
How to make whole-home backup work
If you want the whole house covered, there are four common ways to get there:
- Add output. A second home battery adds its output to the first, which is often enough to cover two AC units at once.
- Soften the AC startup. A soft start on each AC unit cuts its startup surge so the backup can start it easily. We partner with Belton AC to install them.
- Use load management. Smart controls can pause the dryer, water heater or EV charger automatically when the house is busy, so you never hit the limit.
- Run big loads one at a time. In a short outage, simply not running the dryer and oven together is often all it takes.
Where standby generators fit
A properly sized standby generator, often 20 kW or more, has enough output to run most whole homes at once, AC included. That’s the main reason generators are popular for whole-home backup. On natural gas, they also keep running for as long as the gas supply does.
Home batteries and vehicle-to-home systems trade some of that output for silent operation, almost no upkeep and the ability to work on normal days too, like shifting power to cheaper hours or joining grid programs. Many homes choose based on which matters more to them.
Which one is right for you?
| Your situation | Usually the best fit |
|---|---|
| One AC unit, mostly everyday loads | Whole-home backup with a single battery or V2H system |
| Two or more AC units and you want them all | Whole-home with a second battery, soft starts or load management, or a standby generator |
| You want backup that can never overload | Partial backup with a critical loads panel |
| You want the lowest setup cost | Partial backup covering the essentials |
| You worry most about multi-day outages | Battery plus solar, an EV with vehicle-to-home, or a standby generator |
The Texas reality check
Outside major storms, the average U.S. home loses power for about two hours a year in total. Most outages are short, and a single battery or a charged EV covers them easily, whole-home or partial.
Big events are different. Winter Storm Uri and Hurricane Beryl left many Texans without power for days. For those, how long your backup lasts matters as much as what it can run, which is where solar, a large EV battery or a generator earns its place.
How we size your backup
We start with what you want running in an outage, then look at your panel and your actual usage. When it helps, we ask for your 15-minute interval data from your utility to see your real peaks. From there we recommend whole-home or partial backup, and the right battery, vehicle-to-home system or generator to match.
Not sure which backup fits your home?
Tell us what you want to keep running and send a few photos of your panel. We’ll recommend whole-home or partial backup and quote the complete install.
Frequently asked questions
What is the difference between whole-home and partial backup?
Whole-home backup connects your backup to the entire main panel, so any circuit can run within the system’s output limit. Partial backup moves only your essential circuits to a separate backup panel, so only those run during an outage.
Can one home battery run my whole house?
Often, yes, as long as you don’t run every big appliance at once. Many single batteries deliver around 10 to 12 kW, which covers everyday loads and usually one central AC unit. Two AC units, a dryer and an oven together can go past that.
Can my EV back up my whole house?
With a vehicle-to-home system, an EV can back up the whole house or just your essentials, the same as a home battery. Its large battery means it lasts a long time, but it still has an output limit, so the same rules about big loads apply.
Will a battery run my central AC?
Usually one unit, yes. A soft start makes it much easier on the system. Running two or more AC units at once typically needs a second battery, load management or a generator.
Is partial backup cheaper?
Usually. It can work with a smaller system, though moving circuits into a separate backup panel adds some labor. We’ll compare both options in your quote.
Is a generator better for whole-home backup?
A properly sized generator has more output than a single battery, so it runs whole homes more easily. Batteries and vehicle-to-home systems are silent, need almost no upkeep and can work on normal days too. We install both and will recommend whichever fits your home.
Related: Home battery backup · Vehicle-to-home backup · Standby generators