The Complete Guide to Battery Capacity

Portable power stations and solar generators are affordable, eco-friendly devices that provide off-grid and emergency power. There are many different devices, each with varying battery capacities. 

You can narrow your search for a solar generator by determining the required power output and storage capacity. Sizing your ideal system requires a few calculations, including your power requirements, the operating temperature, and the battery type. 

Let’s explore these factors and determine how to calculate the battery capacity you’ll need from a solar generator.

What Is Solar Battery Capacity?

Solar battery capacity refers to the amount of electricity that can be stored in a battery storage system. Storage capacity is typically measured in ampere-hours (Ah), watt-hours (Wh), or kilowatt-hours (kWh).

The greater the solar battery capacity, the more electricity it can store. A high-capacity battery is particularly useful for homes that rely on solar power as their primary source of off-grid electricity.

Factors Affecting Battery Capacity of Solar Generators

Size and Type of Battery

The most significant factor that affects storage capacity is the size and type of battery. Size refers to physical dimensions and volume. In general, larger batteries have higher capacity than smaller ones.

Battery chemistry also plays a crucial role in determining capacity. Different types of batteries have different chemistries and characteristics that impact their performance. For example, lithium-ion batteries typically have higher energy density and capacity than lead-acid batteries of the same size. LiFePO4 (LFP) batteries have a longer lifespan and deeper discharge capacity.


Temperature can significantly impact battery capacity. Most batteries have an ideal temperature range at which they can function. Operating outside of this range may diminish the capacity. 

Lead-acid batteries are highly susceptible to temperature changes and only perform well at room temperature. High and low temperatures cause the reactions in a lead-acid battery to speed up or slow down, respectively. Heat causes it to discharge faster, while cold reduces capacity. 

Lithium Iron Phosphate (LiFePO4) and other Li-ion batteries are less affected by extreme temperatures. For example, the batteries in the RIVER 2 series have discharge and storage temperatures of 14°F to 113°C (-10°C to 45°C). The optimal operating temperature is 68°C to 86°C (20°C to 30°C). 

Battery Age and Condition

As batteries age, their capacity decreases due to usage, temperature, and storage conditions. Ageing leads to a gradual breakdown of active materials and increased internal resistance. Damaged or faulty batteries may also have reduced capacity or not function at all. 

Proper maintenance and usage can extend a battery’s life and capacity. However, all batteries degrade over time.

Types of Solar Generator Batteries

Solar generators may contain any of several types of batteries:

  • Lead-Acid Batteries: These are common in solar generators, cars, and other energy storage applications. They are inexpensive and can withstand deep discharges. However, they are heavy, have a low energy density, and require regular maintenance.
  • Lithium-Ion Batteries: Li-ion batteries are popular due to their high energy density, low weight, and longer lifespan. They are more expensive than lead-acid batteries but require less maintenance and can be discharged deeper without damaging the battery. LiFePO4 is the preferred type of lithium battery for solar applications such as the EcoFlow Power Kits, which use solar panels to generate and store electricity. 
  • Nickel-Cadmium Batteries: Ni-Cad batteries have been used in solar generators for many years. They’re durable, have a long lifespan, and can operate in extreme temperatures. However, they have a lower energy density than lithium-ion batteries and contain toxic materials that harm the environment.

Sizing Your Solar Generator: How Big Should It Be?

The solar generator size you require depends on your electricity consumption. To be on the safe side, you should purchase a system with a power output and storage capacity that exceeds your usage.

To determine the system size you need, you should review your monthly electricity bills to determine your average annual consumption. 

You can also estimate your consumption by adding up the required wattage of your essential appliances. 

Here’s how.

  1. Identify the wattage requirements of your appliances. Survey the starting and running wattage requirements of the appliances and devices you plan to plug into the generator. You can usually find the wattage requirements labelled on the appliance, but we’ve also compiled the starting and running watts of typical household appliances in the table below. 
  2. Convert volts/amps to watts. If your appliance’s power requirements are in volts or amps, you can calculate an appliance’s running watts with this equation: 

Volts (V) x Amps (A) = ​​Watts (W)  

  1. Count the running watts of your appliances. Add up the running watts of the appliances you plan to use — does the total exceed the running watts listed on your generator? If so, you should consider buying a generator with more output capacity.
  2. Factor in starting watt requirements. Identify the appliance with the highest starting wattage. Add that appliance’s starting wattage to the running wattage total.
  3. Calculate the sum. That final number is the total starting watts you need from your generator.  As discussed above, to avoid overloading your generator, do not exceed its starting watts rating.

Starting and Running Watts of Typical Household Appliances 

ApplianceRated (Running) WattsStarting Watts
Washing Machine12002300
Light Bulb60-750
Coffee Maker10000
Clothing Iron15000
Toaster Oven12000
Curling Iron15000
Space Heater20000
20” Box Fan200350

The Relationship Between Battery Capacity and Battery Life

As the capacity of a battery decreases, so does its lifespan. As a battery repeatedly charges and discharges, its capacity and lifespan will gradually degrade.

Maximising Solar Generator Battery Life

Battery maintenance is crucial to maximising your solar generator lifespan. Avoid overcharging or undercharging, store it in a cool and dry place, and use it regularly. 

EcoFlow’s portable power stations use an advanced battery management system (BMS) and LiFePO4 chemistry to ensure maximum durability.

Increasing Solar Generator Battery Capacity

You can increase the storage capacity of some solar generators by adding more batteries. For instance, the DELTA Pro Solar Generator can expand its original storage capacity from 3.6 kWh to a massive total capacity of 25 kWh (or anywhere in between). 


Investing in a solar generator lets you move on from the old days of noisy petrol generators. Instead of burning fossil fuels, solar generators receive power from solar panels, eliminating ongoing fuel costs and helping the environment

Now that you understand how to measure battery capacity, you should be well-equipped to pick out a suitable solar generator. Check out EcoFlow’s innovative solar generators, solar panels, and other products. 


What Is the Relationship Between Inverter and Battery?

An inverter is a balance of system component that converts DC power from solar panels into AC electricity. Without an inverter, such as those built into EcoFlow’s portable power stations, energy captured by solar panels is largely useless.

What Is The Difference Between Battery Capacity and Power Output?

Battery capacity refers to the amount of electricity a battery can store, usually measured in ampere-hours (Ah), watt-hours (Wh), or kilowatt-hours (kWH). Power output measures the maximum wattage a battery system can produce. 
Can You Connect Multiple Batteries To Increase Capacity?
Yes, it is possible to connect multiple batteries to increase capacity. Connecting batteries in series increases voltage while maintaining capacity; connecting them in parallel maintains voltage while increasing capacity. Ensure the batteries have the same voltage and capacity to avoid damage.

How Much kWh Can a Solar Battery Supply?

A typical home solar battery can store anywhere between .25 kWh to 20 kWh of energy, but larger batteries with a capacity of up to 100 kWh are also available for commercial applications. The kWh that the battery can supply also depends on the size of your solar array.

How Long Will a 10 kW Battery Last?

How long a 10 kWh battery will last depends on the amount of energy consumed by the devices connected to it. For example, if a device consumes 1 kWh of energy per hour, a 10 kWh battery would last 10 hours. However, the actual duration may vary based on factors such as battery age and temperature.

Is 10 kWh Enough to Run a House?

A typical household consumes between 18 kWh to 40 kWh per day. A 10 kWh battery may be sufficient to run essential appliances for some households. Evaluate your essential energy consumption requirements when deciding on battery size.

How Many AC Can Run on a 10 kW Solar System?

Air conditioners are power-hungry appliances. The number that can run on a 10 kW solar system depends on running and starting watt requirements.

EcoFlow is a portable power and renewable energy solutions company. Since its founding in 2017, EcoFlow has provided peace-of-mind power to customers in over 85 markets through its DELTA and RIVER product lines of portable power stations and eco-friendly accessories.


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