How Long Does a 100kWh Battery Last? Runtime for Your Home and Appliances
Short answer
A 100 kWh battery gives about 90 kWh of usable energy, enough to run a 1 kW load for about 90 hours or an average US home using 30 kWh a day for about 3 days. At a 5 kW load it lasts about 18 hours. Fully recharging it from empty in one day takes about 65 solar panels of 430 W, or roughly 28 kW of solar.
A 100 kWh battery is ten times the size of a typical single home battery. At this size, storage stops being a backup for a few circuits and becomes a multi-day energy reserve for an entire house, a homestead with no grid connection, or a small business.
This guide shows what a 100 kilowatt hour battery can run, how many days of backup it gives, how much solar it takes to recharge, and what it weighs, costs and needs to pass code.
What is a 100 kWh battery used for?
A 100 kWh battery pack stores 100 kilowatt hours at its nameplate rating. It is used in four main situations:
- Whole-home, multi-day backup. Homes facing long outages from hurricanes, ice storms or wildfire shutoffs ride through several days without a generator.
- Off-grid homesteads. A 100 kWh solar system with a large battery can carry a fully electric off-grid home through two or three cloudy days in a row.
- Small business and commercial sites. Shops, farms and clinics use 100 kWh class cabinets to cut demand charges and protect critical equipment.
- Electric vehicles. Large EV packs sit in the same range. The 2019 to 2020 Tesla Model S Long Range, for example, used a pack of about 100 kWh nominal and about 95 kWh usable.
How long does a 100 kWh battery last?
Runtime depends on two things: how much of the battery you can use, and how fast your loads draw from it. Lithium home batteries usually allow about 90% of rated capacity, so this guide uses 90 kWh as usable.
Example: 100 kWh × 0.90 ÷ 5 kW = 18 hours
Here is how that plays out at common load levels:
| Average load | What that looks like | Runtime | In days |
|---|---|---|---|
| 1 kW | Fridge, lights, internet, well pump cycling | 90 hours | about 3.8 days |
| 3 kW | Most of a home with no electric heat or AC running | 30 hours | 1.25 days |
| 5 kW | Home with central AC or a heat pump cycling | 18 hours | 0.75 days |
| 10 kW | Heavy use: AC, cooking and laundry at once | 9 hours | 0.38 days |
| 20 kW | Peak draw of a large all-electric home or small shop | 4.5 hours | 0.19 days |
Real homes rarely hold one steady load, so use your average draw across the day. Inverters also lose a few percent converting DC battery power to AC, so treat these figures as upper limits. To model your own appliance list, use the battery backup calculator.
Days of backup for an average US home
The average US residential customer buys about 10,791 kWh of electricity a year, or about 899 kWh a month, according to the US Energy Information Administration. That works out to roughly 30 kWh a day.
Example: 90 kWh ÷ 30 kWh per day = 3 days
| Household profile | Daily use | Days from 90 kWh |
|---|---|---|
| Essentials only (fridge, freezer, lights, internet, well pump, fans) | 10 kWh | 9 days |
| Careful whole-home use, no electric heat | 20 kWh | 4.5 days |
| Average US home | 30 kWh | 3 days |
| Large home in summer with central AC | 45 kWh | 2 days |
| All-electric home in winter with resistance heat | 60 kWh | 1.5 days |
Switching to an essentials panel during an outage can stretch the same battery from 3 days to more than a week, without any solar.
How long will a 100 kWh battery run specific appliances?
This table shows how long 90 usable kWh lasts if each appliance runs alone. Power figures are typical ratings, so check your own labels.
| Appliance | Typical power or daily use | Runtime on 90 kWh |
|---|---|---|
| Efficient refrigerator | about 1.5 kWh per day | about 60 days |
| LED lighting, whole house | 100 W | 900 hours |
| Well pump | 1,000 W while running | 90 hours of pumping |
| Space heater | 1,500 W | 60 hours |
| Central air conditioner, 3 ton | about 3,500 W while running | about 26 hours of compressor time |
| Electric water heater | 4,500 W element | 20 hours of heating |
| Level 2 EV charger | 7,200 W | 12.5 hours, about 90 kWh into the car |
Most of these appliances cycle on and off, so real runtime is longer than the continuous figure. A central AC that runs half the time on a hot day, for example, would use about 42 kWh across 24 hours, which is close to half the bank. EV charging can drain the bank in one evening, so lock it out during outages.
How many solar panels does it take to recharge a 100 kWh battery?
Using the site’s standard assumptions of 430 W panels, 4.5 peak sun hours and 80% system efficiency, each panel delivers about 1.55 kWh a day.
Example: 100 ÷ (0.43 × 4.5 × 0.8) = 100 ÷ 1.548 ≈ 65 panels, about 28 kW
Sixty-five residential panels cover roughly 1,350 to 1,400 square feet of module area, more than most roofs hold. And they would only refill the battery: a house also using 30 kWh a day needs about 20 more panels.
In practice, most 100 kWh solar systems only partially recharge the battery each day. A typical 8 kW rooftop array makes about 29 kWh on an average day (8 × 4.5 × 0.8), roughly enough to cover a home’s daily use with little left over. The battery is sized to carry the home through bad weather, then refill slowly over the following sunny days.
To size the array for your own location and loads, try the off-grid solar calculator or the how many solar panels calculator. The battery charging time calculator shows how many hours a given charger or array needs.
How is a 100 kWh battery built?
There are two common ways to reach 100 kWh, and they suit very different buyers.
Stacked residential modules
Most home installs combine several batteries of 5 to 15 kWh each: seven or eight 13.5 kWh units, ten 10 kWh units, or twenty 5 kWh rack modules. This route uses standard home inverters and can be spread across locations, which helps with code limits, but means many units to mount and wire.
Commercial cabinets
Commercial energy storage often comes as a single outdoor cabinet of about 100 kWh or more, with built-in cooling, fire detection and a matched inverter. Cabinets cost less per kWh and take less wiring, but they are built for businesses, farms and utility sites with commercial permits and three-phase or large single-phase service.
Weight and space
Packaged lithium home batteries typically weigh around 20 pounds per kWh, including the case and electronics. At that rate, 100 kWh of storage weighs about 2,000 pounds, roughly the weight of a small car. Stacked units need floor-standing racks or a strong wall, and cabinets usually sit on a concrete pad, with the maker’s listed clearances for cooling and service.
48 V or high voltage: which battery type fits?
Battery voltage changes the current, the cable size and the inverter you can use.
| Design | Typical voltage | Capacity in amp hours for 100 kWh | Current at 10 kW |
|---|---|---|---|
| Low-voltage rack | 51.2 V nominal (48 V class) | about 1,950 Ah | about 195 A |
| High-voltage stack | 400 V | 250 Ah | 25 A |
| Commercial cabinet | about 700 to 800 V | 125 to 143 Ah | about 13 to 14 A |
48 V systems are popular with off-grid builders because server-rack LiFePO4 modules are affordable and work with common off-grid inverters. At 100 kWh the downside is current: 200 A or more needs heavy busbars, thick cables and careful fusing. You can convert between amp hours and kilowatt hours with the kWh to Ah converter.
High-voltage racks run at hundreds of volts, so the same power flows at a fraction of the current. They are the norm for commercial cabinets, and because high DC voltage is dangerous, they should be installed by licensed professionals.
Is a 100 kWh battery allowed in a home?
This is where a 100 kWh battery differs most from a 10 kWh one. In the US, residential energy storage is governed by NFPA 855, which is adopted into the International Residential Code and many state fire codes. For one and two family homes it generally sets these limits:
- Individual units of up to 20 kWh each.
- An aggregate of 40 kWh in a utility closet or storage room.
- An aggregate of 80 kWh in an attached garage, on an exterior wall, or in a detached structure or outdoor ground mount.
A 100 kWh bank therefore exceeds the allowance for any single location. The usual workarounds are splitting the battery between locations (for example, part in the garage and part in a detached structure), or treating it as a larger installation that meets the standard’s full commercial-style requirements. Either route needs early approval from your local building and fire officials, because adopted editions and local amendments vary. Batteries should be listed to UL 9540, and fire officials may also require spacing between units, smoke or heat detection, and impact protection in garages.
How much does a 100 kWh battery cost?
Price depends heavily on the build route. These are typical US ranges in late 2026:
| Route | Typical price per kWh | For 100 kWh |
|---|---|---|
| DIY 48 V LiFePO4 rack modules, batteries only | about $150 to $300 | about $15,000 to $30,000 |
| Commercial cabinet, installed | about $400 to $800 | about $40,000 to $80,000 |
| Stacked residential batteries, professionally installed | about $700 to $1,200 | about $70,000 to $120,000 |
DIY prices exclude inverters, racks, wiring, permits and labor, which can add many thousands of dollars. The 30% federal residential clean energy credit ended for homeowner-owned systems installed after December 31, 2025, so do not count on it for a new home battery. Business owners may have different options and should confirm with a tax adviser. To weigh the cost against bill savings, see the home battery savings calculator.
100 kWh battery vs a backup generator
- Runtime: a generator on natural gas or a large propane tank keeps running as long as fuel arrives. A battery stops at about 90 kWh unless solar refills it.
- Power output: a whole-home generator can carry large motor loads directly. A battery’s output is limited by its inverters, so a 100 kWh bank still needs enough inverter capacity for your peak demand.
- Daily value: a battery can shift solar into the evening, cut time-of-use bills and run silently every day. A generator only earns its keep during outages.
- Upfront cost: a 100 kWh battery costs far more than most standby generators. Many homeowners get better value from a 20 to 40 kWh battery paired with a generator for rare long outages.
If your outages usually last less than a day, a smaller battery sized with the battery calculator often makes more sense than jumping to 100 kWh.
Frequently asked questions
How long will a 100 kWh battery power a house?
About 3 days for an average US home using 30 kWh a day, based on 90 kWh of usable capacity. Limiting use to essentials such as the fridge, lights, internet and well pump at about 10 kWh a day stretches that to roughly 9 days. A large home running central AC may get only 2 days.
How many solar panels do I need to charge a 100 kWh battery?
About 65 panels of 430 W, or roughly 28 kW, to recharge it fully from empty in one average day with 4.5 peak sun hours and 80% efficiency. Most home systems are much smaller and refill the battery over several sunny days instead.
How much does a 100 kWh battery weigh?
Roughly 2,000 pounds for packaged lithium home batteries, which typically weigh around 20 pounds per kWh. Bare cells and DIY rack modules can be somewhat lighter, while commercial cabinets with cooling and enclosures can be heavier. Floor-standing racks or a concrete pad are usually needed.
Can I install a 100 kWh battery at home?
Possibly, but it needs local approval. NFPA 855 generally limits residential units to 20 kWh each and caps the total at 40 kWh in utility rooms and 80 kWh in garages, on exterior walls or outdoors. A 100 kWh bank must be split between locations or meet larger-system requirements.
How much does a 100 kWh battery cost?
Typical late 2026 US ranges are about $15,000 to $30,000 for DIY 48 V battery modules alone, $40,000 to $80,000 for an installed commercial cabinet, and $70,000 to $120,000 for professionally installed stacked home batteries. Inverters, permits and labor change the total a lot.
