How Long Does a 4kWh Battery Last? Runtime for Your Home and Appliances
Short answer
A 4 kWh battery holds about 3.6 kWh you can actually use. That runs a steady 1,000 W load for roughly 3.2 to 3.6 hours, or a fridge, lights, Wi-Fi, a TV and a CPAP from dinner until breakfast during an outage. Three 430 W rooftop panels refill it on a typical sunny day, while a single 200 W camping panel needs about five days.
Four kilowatt hours is the size of the biggest all-in-one portable power stations and of a 12 V 300 Ah lithium battery. It covers a real evening without grid power, yet still fits in a truck for a camping weekend.
This guide works through what a 4 kWh battery will run and for how long, using numbers you can check. It covers an outage night hour by hour, a camping day, the panels that recharge it, and the jobs a battery this size simply cannot do.
How many hours will a 4 kWh battery run?
The label figure is not what reaches your appliances. Lithium batteries hold back a reserve to protect the cells, and this site plans with 90% usable capacity. Anything plugged into an AC outlet also passes through an inverter, which loses roughly another 10%.
Example: 4 × 0.90 × 0.90 ÷ 1.0 kW = 3.24 hours on AC, or 3.6 hours on DC
So a 4 kWh battery gives about 3.6 kWh from its 12 V or USB ports and about 3.24 kWh from its AC outlets. The table shows both at common steady loads.
| Steady load | DC runtime (3.6 kWh) | AC runtime (3.24 kWh) | What draws this much |
|---|---|---|---|
| 50 W | 72 hours | about 65 hours | Router, modem and two LED lamps |
| 150 W | 24 hours | about 21.5 hours | Fridge averaged over a day |
| 300 W | 12 hours | about 11 hours | Fridge, TV, lights and laptop together |
| 600 W | 6 hours | about 5.4 hours | Small window AC running |
| 1,000 W | 3.6 hours | about 3.2 hours | Microwave or a sump pump |
| 1,500 W | 2.4 hours | about 2.2 hours | Space heater or hair dryer |
| 3,000 W | 1.2 hours | about 1.1 hours | Electric oven plus a kettle |
Treat these as planning figures: cold weather, an aging battery and standby draw all trim a little more. To total your own list of appliances, use the battery backup calculator.
Capacity is not the same as power
The kWh rating is stored energy; the inverter’s watt rating is how much can come out at once. A 2,000 W inverter cannot start a 3,000 W load even on a full battery, while a 6,000 W inverter can run it for about an hour.
Can a 4 kWh battery get you through an outage night?
Yes, if you plan it. Federal food safety guidance says a closed refrigerator keeps food safe for only about 4 hours without power, while a full freezer holds for about 48 hours (see the FoodSafety.gov outage chart). That makes the fridge the first thing to put on battery when the lights go out in the evening.
Here is a realistic plan for a 14 hour outage, from 6 pm to 8 am, in a home with gas or no heating demand:
| Load | How it is used | Energy |
|---|---|---|
| Refrigerator (about 1.5 kWh a day) | 14 hours, cycling on and off | 0.90 kWh |
| Microwave, 1,200 W input | 15 minutes to heat dinner | 0.30 kWh |
| Four LED bulbs, 36 W total | 5 hours | 0.18 kWh |
| Router and modem, 20 W | 14 hours | 0.28 kWh |
| TV, 100 W | 3 hours | 0.30 kWh |
| Phones and a laptop | Recharged overnight | 0.15 kWh |
| CPAP without heated humidifier, 40 W | 8 hours | 0.32 kWh |
| Box fan, 50 W | 8 hours | 0.40 kWh |
| Total | 2.83 kWh |
Against 3.24 kWh of AC energy, you reach 8 am with about 0.4 kWh, or roughly 12%, still in the battery. Skip the TV and the fan and you keep about 1.1 kWh in reserve, enough for several more hours of fridge and Wi-Fi if the outage drags on.
Fridges vary by age and size. Our guide to how many watts a refrigerator uses shows how to measure yours with a plug-in meter before you rely on the numbers above.
What a 4 kWh battery cannot do
Size matters most when you look at a whole house. The U.S. Energy Information Administration puts the average residential customer at about 10,791 kWh a year, which is close to 30 kWh a day and an average draw of about 1.2 kW. At that pace, 3.24 kWh of AC energy lasts about 2.6 hours.
Several common loads are out of reach or close to it:
- Central air conditioning. A 3 ton unit draws roughly 3 to 3.5 kW and would empty the battery in about an hour.
- 240 V well pumps and electric ranges. Many power stations offer only 120 V. Some large units, such as models with 120/240 V output, can run them, but the energy still disappears quickly.
- Electric water heaters and dryers. At 4 to 5.5 kW, they exceed the inverter rating on most stations of this size.
- EV charging. At typical EV efficiency of about 3 to 4 miles per kWh, 3.24 kWh adds roughly 10 to 13 miles.
If those loads matter, step up. The 5 kWh battery guide covers a full day of essentials, and the 10 kWh battery guide covers longer whole-home outages.
What kinds of batteries come in 4 kWh?
Three quite different products share this size:
| Type | Real examples | What you get | Best for |
|---|---|---|---|
| Large portable power station | Anker SOLIX F3800 (3.84 kWh), EcoFlow DELTA Pro 3 (4.096 kWh) | Battery, inverter, chargers and outlets in one wheeled case | Renters, outage backup, car camping |
| 12 V lithium battery | 12 V 300 Ah LiFePO4 (3.84 kWh) | Battery only; you add an inverter, charger and solar controller | Vans, boats, trailers, DIY cabins |
| 48 V module or wall battery | 51.2 V 80 Ah rack module (4.1 kWh), small AC-coupled units | Battery that pairs with a hybrid inverter | Starter home systems you plan to expand |
Big power stations are heavy. Anker lists the F3800 at 132 lb, with a 6,000 W continuous output, 2,400 W of solar input and a rating of 3,000 or more cycles. That cycle figure is why lithium iron phosphate (LFP) is now the norm at this size: at one full cycle a day, 3,000 cycles is more than eight years.
How many amp hours is a 4 kWh battery?
Example: 4,000 Wh ÷ 12.8 V = 312 Ah
| Nominal voltage | Amp hours for 4 kWh | Common product | Battery current at 1,000 W AC |
|---|---|---|---|
| 12.8 V | about 312 Ah | 12 V 300 Ah (3.84 kWh) | about 87 A |
| 25.6 V | about 156 Ah | 24 V 150 Ah (3.84 kWh) | about 43 A |
| 51.2 V | about 78 Ah | 48 V 80 Ah (4.1 kWh) | about 22 A |
Current assumes a 90% efficient inverter. The 12 V version needs thick cable and a large fuse, so it fits best where 12 V wiring already exists. Convert other sizes with the kWh to Ah converter.
How long does a 4 kWh battery last on a camping trip?
Off the grid, a 4 kWh battery is more about days than hours. A typical car camping or overlanding day with a 12 V compressor fridge looks like this:
- 12 V compressor cooler: about 0.40 kWh
- Induction burner, 1,500 W for 20 minutes of cooking: 0.50 kWh
- CPAP, 40 W for 8 hours: 0.32 kWh
- Tent or van fan, 30 W for 8 hours: 0.24 kWh
- Laptop, 60 W for 3 hours: 0.18 kWh
- LED string lights and phone charging: 0.10 kWh
That is about 1.74 kWh a day. On 3.24 kWh it lasts close to two days with no charging. Cook on a gas stove instead and daily use falls to about 1.24 kWh, which stretches the battery to roughly 2.6 days.
How much solar keeps you level?
To stop the battery falling day after day, the panels must replace what you use. At 4.5 peak sun hours and 80% system efficiency, each 100 W of panel makes about 0.36 kWh a day.
Example: 1.74 ÷ (4.5 × 0.80) × 1,000 = 483 W, so about 500 W of panels
With one 200 W folding panel, you replace 0.72 kWh a day and the net drain falls to about 1.0 kWh. The battery then lasts roughly three days instead of two. With 400 to 500 W, you can camp indefinitely in good weather.
How long do 100 W to 400 W panels take to recharge a 4 kWh battery?
The table assumes the battery starts empty, needs 3.6 kWh to refill, and gets 4.5 peak sun hours at 80% efficiency.
| Solar input | Energy per sunny day | Days to refill 3.6 kWh | Typical setup |
|---|---|---|---|
| 100 W | 0.36 kWh | about 10 days | One small folding panel |
| 200 W | 0.72 kWh | about 5 days | One suitcase panel |
| 400 W | 1.44 kWh | about 2.5 days | Two 200 W or one 400 W portable panel |
| 800 W | 2.88 kWh | about 1.25 days | Four 200 W panels |
| 1,290 W | 4.64 kWh | under 1 day | Three 430 W rooftop panels |
Example: 4 ÷ 1.55 = 2.6, so 3 panels of 430 W
Two practical checks matter more than the panel count. First, every power station caps solar input by watts and by voltage, so read the spec sheet before wiring panels in series. Second, a DIY 12 V battery needs a charge controller sized to the array: 400 W into a 12.8 V battery pushes about 31 A. Size yours with the charge controller calculator. If you plan to live on a small daily budget, our page on a 4 kWh per day solar system sizes the whole setup.
Charging from a wall outlet
A standard US 15 A, 120 V circuit can supply about 1,800 W at most. A station charging at 1,500 W refills 4 kWh in around 3 hours once charging losses are included, while a slower 500 W charger takes 8 hours or more.
How much does a 4 kWh battery cost?
These are typical US ranges in late 2026. Prices move often with sales, so treat them as a guide only.
- 4 kWh class portable power station: about $1,800 to $3,500 for the unit alone. Bundles with solar panels or a transfer switch cost more.
- 12 V 300 Ah LiFePO4 battery: about $250 to $600 for the battery alone. Add an inverter, a charger, a solar charge controller, cables and fuses.
- Portable solar panels: folding 100 to 400 W panels add a few hundred dollars per panel, depending on wattage and brand.
A 4 kWh battery suits one outage night, a camping weekend or a small cabin. For multi-day storms or central air, step up to a larger, expandable system.
Frequently asked questions
How long will a 4 kWh battery run a refrigerator?
A typical kitchen fridge uses about 1.5 kWh a day. With 3.24 kWh available from the AC outlets, a 4 kWh battery runs that fridge alone for a little over two days. A newer, efficient fridge using 1 kWh a day lasts about three days.
How long will a 4 kWh battery run a CPAP machine?
A CPAP without a heated humidifier draws about 40 W, so it uses about 0.32 kWh over an 8 hour night. On 3.24 kWh, that is roughly 10 nights through the AC outlet. Running it from a 12 V DC adapter avoids inverter losses and adds about one more night. A heated humidifier can cut this by half or more.
Can a 4 kWh battery run an air conditioner?
It can run a small 5,000 to 6,000 BTU window unit drawing about 500 to 600 W for around 5 to 6 hours of compressor time. Central air drawing 3 kW or more would empty it in about an hour, and the startup surge may trip a smaller inverter. For cooling, a larger battery or a generator is the better fit.
Is 4 kWh the same as 4 kW?
No. Kilowatt hours (kWh) measure stored energy, like the size of a fuel tank. Kilowatts (kW) measure how fast energy flows, like the size of the fuel line. A 4 kWh battery with a 2 kW inverter can deliver 2,000 W at once for about 1.6 hours. Always check both the capacity and the continuous output rating.
How many solar panels do I need to charge a 4 kWh battery?
Using 4.5 peak sun hours and 80% system efficiency, three 430 W panels refill a 4 kWh battery in one sunny day. With portable gear, 400 W of panels takes about two and a half days and a single 200 W panel about five days. Cloudy weather or winter sun can double those times.
