AmpHour (Ah) Or WattHour (Wh)? How To Properly Spec Energy Storage
As we move into an era with an everincreasing focus on renewable energy, it is more important than ever to understand how to spec energy storage properly. There are many different ways to store energy, but the two most common units of measurement are the amphour (Ah) and the watthour (Wh).
But what’s the difference between the two, and how do you know which one is right for your needs? Let’s look at the difference between amphour and watthour and how to specify energy storage correctly.
Understanding AmpereHour (Ah)
The amperehour, or Ah, is a unit of measurement that refers to the amount of time that a current can be maintained over a given period. For example, let’s say you have a battery that can maintain a current of 1 amp for 10 hours. That would mean that the battery has a capacity of 10 Ah.
This is the most common unit of measurement for batteries, as it indicates how long the battery will last to maintain a particular current.
However, it’s important to note that the Ah does not indicate how much power the battery can store. It’s only a measure of how long it can maintain a specific discharge rate.
For example, let’s say you have a battery with a 2 Ah rating. This means that, at a discharge rate of 1 Amp, the battery will last for 2 hours. However, if you try to draw a current of 2 Amps from the same battery, it will only last 1 hour. This is because the battery is being discharged at twice the rate that it’s rated for.
So, how do you know how many Ah your battery can provide? The best way to find out is to check the manufacturer’s specifications.
This will give your battery the Ah rating and maximum discharge rate. From there, you can calculate the maximum current your battery can provide.
Specifying Energy Storage In AmpHours
Now that you know how to correctly measure battery capacity in Ah, let’s talk about how to specify energy storage. When specifying energy storage, you need to take into account several factors, such as:
 The total amount of energy that you need to store
 The discharge rate that you’ll be using
 The voltage of the system
For example, you need to store 10 kWh of energy. You also know that you’ll be using a discharge rate of 1 kW and that your system voltage is 48 V. To calculate the amount of storage you need in Ah, you would use the following equation:
Ah = Wh / (V x I)
Therefore, Ah = 10 kWh / (48 V x 1 kW)
Ah = 208.33 Ah
This means you would need a battery with a capacity of 208.33 Ah to store the energy you need correctly.
As you can see, the Ah rating is just one factor to consider when specifying energy storage. You also need to consider the voltage of your system and the discharge rate you’ll be using.
You can only accurately specify the energy storage you need by considering these factors.
What Is A Milliamperehour (mAh)?
Just like how you would measure the amount of water in a bucket in terms of gallons or liters, the capacity of a battery is typically measured in amperehours (abbreviated as Ah). One Ah equals 3600 Coulombs, equal to the charge on 6.28 x 10^18 electrons.
The milliamperehour, or mAh, is simply onethousandth of an Ah. This makes it a more convenient unit of measurement for smaller batteries. For example, many cell phone batteries are rated in mAh.
To convert from Ah to mAh, multiply by 1000. For example, a battery that has a capacity of 3 Ah would have a capacity of 3000 mAh.
Similarly, to convert from mAh to Ah, divide by 1000. For example, a battery with 3000 mAh would have a capacity of 3 Ah.
Understanding Watthour (Wh)
Have you ever wondered how many watts your TV uses? Or how much power your toaster consumes? The answer is simple: look at the wattage rating.
The wattage rating is simply the amount of power a device uses, measured in watts. For example, a 100watt lightbulb will use 100 watts of power.
The watthour, or Wh, is a unit of energy. It’s equal to the amount of power used over some time, measured in hours. For example, if you have a 100watt lightbulb and use it for 1 hour, then you’ve used 100watt energy.
You can use the watthour to measure the amount of energy used by anything that uses power, such as your TV, your toaster, or even your car. While the wattage rating tells you how much power a device uses, the watthour tells you how much energy it uses.
Now that you know the difference between watts and watthours, let’s look at how to specify energy storage correctly.
Specifying Energy Storage In WattHours
When specifying energy storage, it’s essential to consider the discharge rate you’ll be using. For example, you need to store 10 kWh of energy. You also know that you’ll use a discharge rate of 1 kW. To calculate the amount of storage you need in Wh, you would use the following equation:
Wh = Ah x V
Therefore, Wh = 10 kWh / (1 kW)
Wh = 10,000 Wh
This means you would need a battery with a capacity of 10,000 Wh to store the energy you need correctly.
As you can see, the watthour is a more convenient unit of measurement for specifying energy storage. When specifying storage in watthours, you don’t need to consider your system’s voltage. This makes it a more straightforward and more accurate way to specify energy storage.
When specifying energy storage, always use the watthour as your unit of measurement. This will ensure that you have enough storage for your needs.
To recap, here’s what you need to remember when specifying energy storage:
 The total amount of energy that you need to store (measured in watthours)
 The voltage of your system
 The discharge rate that you’ll be using (measured in watts)
You can only accurately specify the energy storage you need by considering these factors.
Why Does It Matter?
Now that you know how to specify energy storage correctly, you might wonder why it matters.
But, understanding energy storage is essential because it’s a critical factor in designing efficient and effective electrical systems.
For example, let’s say you’re designing a solar system for a home. One of the first things you need to do is determine the energy the system will need to generate. This is where your knowledge of watthours comes in handy.
By understanding how to specify energy storage correctly, you can ensure that your solar system is designed to meet the specific needs of your home.
While most people don’t need to worry about specifying energy storage, it’s still a good idea to understand the concept.
However, there are some situations where it’s essential to get the specification right. For example, if you’re designing a solarpowered system, you’ll need to ensure that your energy storage system can handle the daily fluctuations in solar output.
Another example is if you’re designing a system that will be used in an offgrid application. In this case, it’s critical to ensure that your system can store enough energy to meet your needs, even during cloudy weather.
So, while most people don’t need to worry about specifying energy storage, there are some situations where it’s essential to get it right.
For example, suppose you’re designing a solarpowered or offgrid system. In that case, you’ll need to consider the daily fluctuations in solar output or the possibility of extended periods of cloudy weather.
What Is The Right Number Of AmpHour Or WattHour For My Power Station?
Now that you know how to specify energy storage correctly, you might wonder what the right amphour or watthour is for your power station. The answer depends on a few factors, such as:
– The capacity of your solar panels
– The capacity of your wind turbine
– The average daily sunlight hours
– The average daily wind speed
– Your power usage
Let’s say you have a solar panel with a capacity of 100 watts. This means that, in ideal conditions, your solar panel can produce 100 watthours of energy per hour. However, due to the nature of sunlight, you’ll only be able to produce this much energy for a portion of the day.
On average, you can expect to produce around 4 hours of peak sunlight per day. Your solar panel will produce an average of 400 watthours of energy per day. This is the equivalent of 1.6 kilowatthours (kWh).
From this, you can see that the average daily output of your solar panel will be 1.6 kWh. However, this is only an average. Your solar panel will produce more energy on some days and less on others.
Most people use between 10 and 30 kWh of energy per day. This means that if you’re only relying on solar power, you’ll need at least six solar panels to meet your needs, each producing an average of 1.6 kWh per day.
Of course, this is only a rough estimate. The actual number of solar panels you’ll need will depend on several factors, such as your power usage and the average daily sunlight hours in your area.
Frequently Asked Questions

How do you calculate the energy stored in a battery?
The total energy stored in a battery is equal to the product of its voltage and capacity in amphours (Ah). To calculate a battery’s watthour (Wh) storage capacity, multiply the voltage by the Ah rating. For example, a 12volt battery with a 20 Ah rating would have a total energy storage capacity of 240 watthours (12 volts x 20 Ah = 240 Wh).

Does a higher Ah battery give more power?
No, the power output of a battery is determined by its voltage, not it’s Ah rating. The Ah rating is a measure of the battery’s capacity or how much energy it can store. A higher Ah battery will have a higher capacity than a lower Ah battery but will not provide more power. It would be best if you increased the voltage to get more power from a battery.

What is the difference between battery capacity and rated capacity?
The capacity of a battery is its ability to store energy, measured in amphours (Ah) or watthours (Wh). The rated capacity of a battery is its nominal capacity or the amount of energy it is designed to store. The actual capacity of a battery may be lower than its rated capacity. It is due to age, temperature, and discharge rate.

How are storage batteries rated?
Storage batteries are rated according to their capacity, voltage, and current. Capacity is usually measured in amphours (Ah), while voltage and current are measured in volts (V) and amperes (A), respectively. For example, a battery with a capacity of 100 Ah and a voltage of 12 V can deliver 1 A of current for 100 hours or 10 A for 10 hours before recharging.
Current ratings are usually given for two different discharge rates: the “constant” or “nominal” rate and the “peak” or “surge” rate. The constant rate is the average current the battery can deliver over a long period, while the peak rate is the maximum current the battery can deliver for a short time.

How do you size an energy storage system?
When sizing an energy storage system, you need to consider two things. First is the desired capacity of the system and the desired power output of the system. The capacity is determined by the amount of energy you want to be able to store and is usually specified in amphours (Ah) or watthours (Wh). The power output is determined by the amount of power you need. It is to be able to deliver and is usually specified in watts (W).
To size an energy storage system, you need to know the following:

The desired capacity of the system in Ah or Wh

The desired power output of the system in W

The voltage of the system

The discharge rate of the battery

The temperature range of the system
The first step is to calculate the capacity of the battery. You can have it by multiplying the desired capacity by the discharge rate. For example, if you want a system with a capacity of 100 Ah and a discharge rate of 0.5C, you would need a battery with a minimum capacity of 50 Ah.
The second step is to calculate the power output of the system. This is done by multiplying the battery’s capacity by the system’s voltage. For example, if you have a battery with a capacity of 50 Ah and a voltage of 12 volts, the power output of your system would be 600 watts (50 Ah x 12 volts = 600 watts).
The third step is to calculate the temperature range of the system. You can multiply the system’s power output by the battery’s temperature coefficient. For example, if you have a system with a power output of 600 watts and a temperature coefficient of 0.5%, the temperature range of your system would be three °C (600 watts x 0.5% = 3°C).
The fourth and final step is to select a battery with a capacity and voltage that meet your needs. Now that you know how to spec energy storage properly, you can start shopping for the right system.

What size battery do I need for a 10kw solar system?
The answer to this question depends on how you plan to use your solar power system. If you want to offset your energy usage from the grid, you will need a battery with a capacity of at least 28 kWh. However, if you want to disconnect from the grid completely, you will need a much larger battery.
Conclusion
Now that you know how to specify energy storage correctly, you can ensure that your system has the proper storage for your needs. This is important for ensuring that your system can meet your power needs, even on days when solar output is low or during extended periods of cloudy weather.
While most people don’t need to worry about specifying energy storage, there are some situations where it’s essential to get it right. So, if you’re designing a solarpowered or offgrid system, consider the daily fluctuations in solar output or the possibility of extended periods of cloudy weather.
Considering all these factors, you can ensure your system has the proper energy storage to meet your needs.