Amp-hours, or Ah, is a measure of how long a solar battery can power your home’s appliances before it’s completely drained. If you’re considering battery storage for your solar system, you’ve likely come across this term as well as other measurements, such as voltage and watts. Understanding these key metrics can help you better understand a battery’s storage capacity, efficiency, and how much power it can supply over time.
In this blog, we break down key solar battery specifications like volts, amps, and watts, explain what amp-hours are, how they compare to kilowatt-hours, and other essential solar battery specs to check when considering solar energy storage for your home.
Key takeaways:
- Voltage measures electrical force, amperage describes the flow of electricity, and wattage indicates the total power being used or generated.
- Amp-hours (Ah) measure how long a solar battery can power your home based on the electrical current it can provide over time. This can help you understand how long a solar battery will last before needing a recharge.
- While amp-hours show how long a battery will last under specific conditions, kilowatt-hours provide a broader measure of total energy capacity, making it easier to compare solar batteries and match them with your home's energy needs.
- Other important solar battery specifications include power rating (kW), depth of discharge (DoD), round-trip efficiency, cycle life, and warranty.
Voltage vs amperage vs watts
Volts, amps, and watts are measurements that give insight into how energy moves through a system. If you’re looking to purchase solar batteries, understanding these key electrical terms can help you choose the best components for your home.
Below, we break down how voltage, amperage, and watts work together to provide power to and from your solar battery.
Voltage
Voltage refers to the amount of electrical force pushing through a wire. One easy analogy to understand this is to picture water running through a garden hose.
In this analogy, voltage is the pressure of the water in the hose. Whether water is flowing through the hose or not, the pressure is always present. This is similar to voltage, which is the energy potential, or how much force is ready to be used.
When it comes to solar batteries, voltage helps indicate which appliances you can safely connect to. For example, a 120V battery is compatible with 120V appliances. This makes voltage an important factor in making sure your system’s components work together.
Amperage
Amperage, or amps, describes the flow of electricity through a wire. While voltage is the pressure of water in the hose, amperage is the amount of water that’s flowing through.
When attaching electrical components, amperage tells you how big a wire needs to be. In the hose analogy, amperage would represent the thickness of the hose, which determines how much water can pass through at once. The larger the hose, the more water it can carry – just like how thicker wires can handle more electricity.
When you’re connecting appliances to a battery, the amperage tells you the size of the wire needed. If the wire isn’t large enough, it could overheat and potentially create a safety hazard. These are the details that matter, and the reason you choose a licensed and certified installer when adding solar or a battery to your home.
To summarize:
- Voltage: Measures electrical pressure or force.
- Amperage: Measures how much electricity flows through the system.
Both are essential for determining the compatibility of your system’s components – a 12V solar battery, for example, should only be connected to 12V appliances.
Wattage
Watts describe the total amount of energy flowing through a system. You can calculate watts by multiplying voltage with amperage. Essentially, watts show how voltage and amperage work together to determine power output (watt rating).
Let’s go back to the water hose analogy, only this time we have two hoses: one with high pressure (voltage) but smaller diameter (amperage), and another with low pressure and a larger diameter. Even though they differ in size and pressure, both can fill a bucket in the same amount of time. That’s because they deliver the same power – or wattage.
In a solar power system, you can have different combinations of voltage and amperage but still produce the same wattage. For example:
- A solar panel producing 10 volts and 1 amp will give you 10 watts of power.
- A solar panel producing 1 volt and 10 amps will also provide 10 watts.
Although the voltage and amperage differ, the total wattage remains the same. The only difference is that higher amperage will require a thicker wire to safely carry the load. This is why amp ratings alone don’t tell the full story of how much power a battery can supply. Both voltage and amperage are needed to properly understand the full capacity of a system.
See More: How To Choose a Home Battery Backup System?
What is an amp-hour?
An amp-hour or ampere-hour (Ah) tells you how much charge a battery can hold over time. It measures the amount of current (amps) that a battery can provide over a specific period (hours). Think of it like the fuel tank for your solar battery – it lets you know how long the battery can power your home before it needs to be recharged.
Let’s break it down: if you have a battery rated for 10 amp-hours, it means the battery can deliver 1 amp of current for 10 hours, or 2 amps of current for 5 hours, and so on. Essentially, amp-hours show you how long the battery will last under a specific electrical load. A higher Ah battery will be able to supply your home with power for longer.
Remember that a battery’s amp hour rating only tells you part of the story. To understand the full picture of battery capacity, you’ll need to consider volts as well. That’s where kilowatt-hours (kWh) come in. This is the most common measurement for solar batteries because it accounts for both voltage and amps.
What is a kilowatt-hour?
A kilowatt-hour (kWh) measures the energy consumed by an appliance over a certain period of time. If you look at your electricity bill, you’ll see your energy consumption measured in kilowatt-hours. One kilowatt-hour is equivalent to 1,000 watts of power used for one hour (or 1,000 watt-hours).
Kilowatt-hours are calculated by multiplying wattage by the number of hours an appliance is used. If you use a 1,000 watt appliance for an hour, that’s 1,000 watt-hours or one kilowatt-hour. If you used the same appliance for 10 hours, that’s 10 kWh.
You can use kilowatt-hours to understand how much electricity an appliance or solar panel is generating or consuming over time. You can also use it to determine how much power a solar battery can store. It is a much easier way to evaluate solar batteries as you can compare the kWh with your energy usage and the power your solar system generates to understand how long your appliances will be powered for.
Amp-hours vs kilowatt-hours
Both amp-hours (Ah) and kilowatt-hours (kWh) measure energy, however they represent different aspects of it:
- Kilowatt-hours tell you the total amount of energy a battery can store. Because they align with how your energy consumption is measured on utility bills, they’re easier to relate to your home’s needs.
- Amp-hours indicate how much current a battery can deliver over time. It’s a more technical metric that comes into play when you’re designing a system or choosing a battery that matches the voltage requirements of your solar setup.
If you’re just looking at energy storage, focus on kWh. Amp-hour ratings are useful if you’re trying to get into the nitty-gritty of system design or comparing battery specifications. If that’s not your goal, sticking with kWh will give you the clearest picture.
Keep Reading: AC vs DC-Coupled Battery Storage: What You Need to Know
How to convert amp-hours to kilowatt-hours
Kilowatt-hours are calculated by multiplying amp-hours by the battery’s voltage. Here’s a formula you can use to convert amp-hours to kilowatt-hours:
kWh = Ah x voltage / 1000
For example, if you’re looking at a 50V battery with a capacity of 100Ah:
kWh = 100Ah x 50V / 1000 = 5 kWh.
Other solar battery specifications to check
Understanding amp-hours and kilowatt-hours can be useful when choosing a solar battery for your home, but there are other key specs to consider, including power rating, DoD, and type of battery.
Power rating (kW)
A solar battery’s power rating tells you how much power a battery can deliver at a given moment, measured in kilowatts (kW). This can help you understand how many appliances or devices can run simultaneously.
Solar batteries with higher power ratings allow you to run more energy-hungry appliances, such as air conditioners or washing machines, at the same time. Batteries with lower power ratings will only be able to handle a limited load.
Depth of discharge (DoD)
Depth of discharge refers to how much of a battery’s capacity can be used before it should be recharged. Most batteries have a DoD limit to prevent damage and extend their lifespan. The higher the DoD limit, the more of a battery’s capacity you can use.
If a battery has 90% DoD, for example, you can use 90% of its energy before it needs to be recharged. Lithium-ion and flow batteries tend to offer the highest DoD, meaning you can use more stored energy at a time.
Continue Reading: How Many Batteries Do You Need To Run a House on Solar?
Battery type
The three main types of solar batteries are lead-acid, lithium-ion, or flow batteries. Each of these has their own unique advantages and disadvantages. For example:
- Lead acid batteries are more affordable but have a shorter cycle life and lower DoD.
- Lithium-ion batteries are more efficient, last longer, and have a higher DoD.
- Flow batteries are long-lasting and have 100% DoD but are more expensive than the other two options.
Round-trip efficiency
Round-trip efficiency tells you the percentage of energy lost during the charging and discharging process. No battery is perfectly efficient and there'll always be small amounts of energy lost during operation.
For example, a battery with 95% round-trip efficiency will provide 95 units of usable energy for every 100 units put in during charging. The remaining 5% will be lost as heat or some other form of inefficiency. Look for batteries with high round-trip efficiency as it means they’ll lose less energy during the storage process.
Cycle life
A battery’s cycle refers to one full charge and discharge. Cycle life indicates how many of these cycles a battery can perform before its capacity starts to decrease. Batteries with a longer cycle life will generally last longer.
Warranty
Warranty tells you how long the manufacturer guarantees battery performance. Usually, solar battery warranties will cover either a set number of years or a specific number of charging cycles – whichever comes first. Some manufacturers use throughput measured in kilowatt hours for their warranty as opposed to number of cycles. It’s always best to review the battery warranty in detail for ask your battery consultant for the correct metric.
For example, a battery might come with a warranty of 10,000 cycles or 10 years. This means the manufacturer guarantees the battery will last for 10,000 full charge and discharge cycles, or for 10 years, depending on which one you reach first. If you hit 10,000 cycles before the 10-year mark, the warranty would expire at that point, and vice versa.
Summary: Understanding battery amp-hours
When choosing a solar battery, understanding amp-hours (Ah) is just the beginning. While Ah helps you gauge how long a battery will power your home, it’s important to also consider other specifications like voltage, watts, kilowatt-hours (kWh), and factors like power rating, depth of discharge (DoD), and round-trip efficiency. Each of these plays a role in helping you understand how well a battery will meet your energy needs, how long it will last, and how efficient it will be over time.
With so many solar batteries available on the market, it can be difficult to compare and evaluate the right one for your unique circumstances and energy goals. That’s where we come in! You don’t have to wrap your head around these specifications alone. At Sun Valley Solar Solutions, we offer free, no-obligation consultations with our solar experts to help you determine the best solar battery setup for your needs.
Whether you're after a whole home backup system or backup during outages, our solar consultants are available to provide advice on the most suitable solar battery for your needs. Contact us today to schedule your consultation.