Wh vs Ah: The Difference in Watt hours and Amp hours

With the need for energy storage, you also need to understand the concepts and differences between Watt hours and Amp hours (Wh vs Ah).

Off-grid power backup is already a hot topic. When traveling far away in an RV or boat, the solar energy storage system can solve the problem of electricity consumption on the road, and you can replenish electricity at any time no matter where you go. Or maybe the area where you live is often short of electricity and the electricity bill is expensive, so you need to build a solar system to maintain daily electricity consumption.

What is the difference between Ampere Hours and Watt Hours?

An energy storage system is a system that often includes batteries and conversion units such as inverters, chargers, etc. Generally speaking, Ah is used for the capacity of batteries or battery packs, while Wh is mostly used for the energy of energy storage systems. The biggest difference between them is that Wh considers batteries voltage, while Ah is not considered.

Watt hours – Energy unit

Watt hours are commonly used on household electricity meters, and most electricity supply formulas calculate electricity bills in watt hours or kilowatt-hours.

household electricity meters

Watt hours is a unit that describes the change of energy, that is, the change of power over time. Watt is the unit of power, and each watt is equivalent to 1 joule per second. Watt hour (Wh) is a unit of energy used to express the amount of electrical energy used over time. Watt-hours are obtained by multiplying the wattage of an electrical device by the number of hours of use. For example, if a 1000 watt air conditioner needs to be used for 3 hours a day, the power consumption can be calculated as 1000W x 3h = 3000Wh.

Amp hours – Capacity unit

Amp hour (AH) is a common unit of battery capacity. Smaller capacity batteries use milliamp-hours (mAh, conversion: mAh = 0.001 * Ah). Amp hour is the change of charge amount over time, Watt hours is for measure of energy, then Ampere hour (Ah) is a unit of capacity, representing the current used over a period of time (time measured in C-rate).

Calculating ampere hours requires knowing the current flow. If the discharge rate is 1C, the ampere hour is the capacity of the current that lasts for 1 hour. For example, a 100Ah, 1C battery can discharge 100A for 1 hour. A 100Ah, 2C battery can discharge 200A for 0.5 hours. Simply put, Ampere Hours refers to the amount of current that can be delivered over a period of time.

Regarding discharge time, you need to understand C rate. Battery discharge rate is the unit of complete charge and discharge speed. For example, 1C discharge means that the battery capacity can be discharged from 100% to 0% in 1 hour. 2C discharge rate represents 0.5 hours of discharge. time.

How to convert between Wh vs Ah?

Convert Amp hours to Watt hours

Because W (power) =A (current) x V (voltage) in Watt’s law, ampere-hours and watt hours can be converted to each other. The calculation of kilowatt-hours needs to be multiplied by 1000 to calculate the Ah to Wh formula:

  • Watt hours (Wh) = Ampere-hour (Ah) x voltage (V),
  • Kilowatt-hour (kWh) = Ampere-hour (Ah) x Voltage (V) x 1000.

If your RV has a 12V 100Ah battery, then multiply 12V by 100Ah to get an energy value of 1200Wh. Your battery can provide 1200Wh of power to the device.

Convert Watt hours to Amp hours

The formula to derive ampere-hours from watt hours, Wh to Ah:

  • Ampere hours = Watt hours (Wh) / Voltage (V)

If the energy storage system requires 3600Wh of energy storage, then if you choose a 12V battery, divide 3600Wh by 12V to get 300Ah. You can choose 12V 300Ah battery or battery pack.

To make your calculations easier, we’ve created an Wh vs Ah converter.

Why do you need to know the calculation of Wh vs Ah?

If you are planning to install a solar and energy storage system, you first need to calculate the watt hours consumption of all electrical equipment. Through equations, you can derive the planning requirements for the solar system and energy storage system.

In addition to the watt hours value of the electrical equipment, it also needs to be able to match the capacity of the battery. It is very important to determine the battery capacity required for the operation of the equipment.

By calculating the amp hours or watt hours required per day, you can plan the parameters of the solar system in advance based on your needs and select the appropriate solar system and battery. Otherwise, the actual power consumption cannot be confirmed, resulting in power shortage or insufficient power, and power cannot be replenished immediately.

energy storage system

Before planning to build an energy storage system, in order to make correct decisions and plans, calculate Ampere Hours and Watt Hours help determine the battery capacity and the power consumption of electrical equipment, which involves the accessories required for the solar system, such as the number and type of batteries, the number and wattage of solar panels, And the choice of the thickness of the connecting line, etc. Only by calculating the correct demand can you make wise decisions, and the backup power can ensure your normal use of electricity every day.

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