How Long Will My Home Battery Last During a Blackout?
One of the first questions homeowners ask after installing a battery is:
"If the power goes out, how long will my battery keep the house running?"
The honest answer is:
It depends entirely on how much electricity you're using.
A battery's runtime is determined by two things:
The battery's usable storage capacity (kWh)
The amount of power your home is consuming (kW)
Think of it like a fuel tank in a car. The larger the tank, the further you can drive. But your fuel consumption has a huge impact on how long that fuel lasts.
Understanding Battery Capacity
Battery capacity is measured in kilowatt-hours (kWh).
For example:
Sungrow BatteryCapacity
SBR096 = 9.6 kWh
SBR128 = 12.8 kWh
SBR160 = 16.0 kWh
SBR192 = 19.2 kWh
SBR224 = 22.4 kWh
SBR256 = 25.6 kWh
The higher the kWh rating, the more energy the battery can store.
A Simple Runtime Formula
A rough estimate can be calculated using:
Battery Capacity ÷ Average Load = Runtime
For example:
12.8 kWh battery ÷ 1 kW household load = 12.8 hours
This provides a useful guide, although actual results will vary depending on appliance usage and battery reserve settings.
Example 1: Essential Loads Only
Many Sungrow backup systems are configured to power only critical circuits during a blackout.
Typical essential loads:
Refrigerator
Internet modem
Lighting
Television
Phone chargers
Average demand:
400–600 watts (0.4–0.6 kW)
Using an SBR128 battery:
12.8 kWh ÷ 0.5 kW = approximately 25 hours
In this scenario, many households can comfortably get through an overnight outage and well into the following day.
Example 2: Average Evening Usage
A typical family may be running:
Fridge
Lights
TV
Wi-Fi
A few kitchen appliances
Average demand:
1.0–1.5 kW
Using a 12.8 kWh battery:
Average LoadEstimated Runtime1.0 kW12.8 Hours1.5 kW8.5 Hours
This is enough to carry many households through an evening blackout.
Example 3: Heavy Household Loads
Now let's add some larger appliances:
Air conditioner
Oven
Multiple appliances
Pool equipment
Average demand:
3–5 kW
Using a 12.8 kWh battery:
Average LoadEstimated Runtime3 kW4.3 Hours5 kW2.5 Hours
The battery drains much faster because power consumption has increased significantly.
What Uses the Most Power?
Many homeowners are surprised by how much power certain appliances consume.
ApplianceTypical Power DrawLED Lighting50–200 WRefrigerator100–300 WTelevision100–250 WWi-Fi Router10–20 WMicrowave1,000–1,500 WKettle2,000–2,400 WOven2,000–4,000 WAir Conditioner1,000–4,000 WEV Charger7,000 W+
A kettle may only run for a few minutes, but an air conditioner running continuously can dramatically reduce battery runtime.
Will Solar Panels Help During a Blackout?
If your Sungrow system includes backup functionality and the sun is shining, your solar panels can recharge the battery and assist with powering loads during the outage.
This can significantly extend runtime.
For example:
Battery starts morning at 50%
Solar begins producing energy during the day
Household loads are supplied by solar
Excess solar recharges the battery
In some situations, a home can remain powered for multiple days during an extended outage if solar production exceeds consumption.
Bigger Batteries Last Longer
Let's compare runtimes assuming an average household load of 1 kW.
Battery SizeRuntime9.6 kWh9.6 Hours12.8 kWh12.8 Hours19.2 kWh19.2 Hours25.6 kWh25.6 Hours
This demonstrates why larger battery systems are becoming increasingly popular for households wanting greater energy independence.
The Most Important Thing to Remember
Many people focus on battery size and forget about consumption.
A 12.8 kWh battery can last:
More than 24 hours for essential loads
Around 8–12 hours for normal household use
Only a few hours if running high-demand appliances continuously
The secret to long blackout protection isn't just installing a larger battery—it's managing what you run during the outage.
Final Thoughts
The runtime of your Sungrow battery depends on both its capacity and the amount of electricity your home is using at the time. For most households running essential loads, a properly sized battery can provide many hours of backup power and often carry the home through an overnight outage.
If your goal is to maximise blackout protection, focus on three things:
Choosing the right battery size
Designing an effective backup circuit
Managing large electrical loads during outages
Remember:
The battery determines how long the backup lasts. The inverter determines how much you can run at once.