If you’re exploring home battery storage—especially in combination with solar panels—you’re likely to come across a lot of unfamiliar terms. The technical lingo can be intimidating, but understanding a few key concepts can make your decision much easier. This guide breaks down the essential terms so you can shop with confidence.
Nominal Capacity vs. Usable Capacity Batteries
Usually list two types of capacity:
Nominal (or total) capacity is the maximum amount of energy a battery can theoretically store, measured in kilowatt-hours (kWh).
Usable capacity refers to how much of that energy is actually available for your home’s use.
Because batteries reserve a small portion of their charge to preserve long-term performance, the usable capacity is always slightly lower. For example, a battery rated at 13.44 kWh total capacity might only offer 13 kWh of usable energy. This smaller number is the one that really matters for everyday use.
Understanding Depth of Discharge (DoD)
Depth of Discharge (DoD) shows what percentage of a battery’s energy can be safely used before it should be recharged. It’s typically shown as a percentage—so a battery with a 90% DoD means you can use 90% of its total capacity.
Let’s say your battery has a 10 kWh capacity and a 90% DoD; you can access 9 kWh before recharging. Lithium-ion batteries generally offer high DoD levels, often between 90% and 95%, but it’s always smart to check product datasheets and warranty terms.
Backup Reserve: Planning for Outages
Many battery systems let you reserve a portion of stored energy exclusively for backup during power outages—this is called a backup reserve.
For example, if your 13 kWh battery has a 20% reserve set, only 10.4 kWh is available for regular daily use. The remaining 2.6 kWh is saved for emergencies. This reserve setting is often adjustable in your battery’s control panel.
Capacity Degradation Over Time
Like all rechargeable devices, home batteries gradually lose capacity over time. This natural wear-and-tear is called degradation, and it means your battery won’t hold as much energy in year 10 as it did in year 1.
Battery manufacturers usually include a performance warranty. A common example might guarantee 70% of original capacity after 10 years, although some warranties may drop to 50–60%. So if your system is perfectly sized for your current needs, remember to plan for slightly less performance in the future.
How to Choose the Right Battery
Before making a purchase, ask your installer or retailer to explain these terms and how they apply to the battery you’re considering. Request transparent performance data based on real-world usage, and thoroughly review the warranty terms.
Depth of Discharge (DoD): The proportion of a battery’s total energy that can be utilized before it needs to be recharged.
By understanding these simple yet important terms, you’ll be better equipped to select a battery that meets both your current and future energy needs—with no surprises down the line.
By following these tips, you’ll be able to find the right solar system and enjoy clean, cost-saving energy. For more advice, visit Revolusun Power (https://revolusunpower.com.au/).
