What is Depth of Discharge (DoD)?
The share of a solar battery's capacity you can safely use, expressed as a percentage of its total size.
Quick Answer
When comparing solar batteries in the UK, check usable capacity rather than just the nominal size, as DoD varies between products. Most popular UK home batteries (Tesla Powerwall, GivEnergy, FoxESS) use LFP cells with high DoD, so usable capacity is close to the rated figure.
Fact-checked by John Rooney, Solar Energy Editor. Editorial policy
Depth of Discharge (DoD) Explained
Depth of Discharge (DoD) is the percentage of a battery's total capacity that can be used before it needs recharging. A 10 kWh battery with 90 percent DoD gives 9 kWh of usable energy. Discharging beyond the recommended DoD shortens a battery's life. Modern lithium iron phosphate (LFP) batteries typically allow 90 to 100 percent DoD, much more than older lead-acid types, which is why usable capacity often matches or nearly matches the headline figure.
How Does Depth of Discharge (DoD) Work in the UK?
When comparing solar batteries in the UK, check usable capacity rather than just the nominal size, as DoD varies between products. Most popular UK home batteries (Tesla Powerwall, GivEnergy, FoxESS) use LFP cells with high DoD, so usable capacity is close to the rated figure.
Frequently Asked Questions
What is a good depth of discharge for a solar battery?
For modern lithium iron phosphate (LFP) home batteries, 90 to 100 percent DoD is normal and safe. That means almost all the rated capacity is usable. Older lead-acid batteries were limited to around 50 percent to protect their lifespan.
Does depth of discharge affect battery life?
Yes. Regularly discharging a battery beyond its recommended DoD shortens its life. Manufacturers set a safe DoD and design the battery management system to enforce it, so within the rated usable capacity you do not need to worry.
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John Rooney is the founder of Solar Info and has been covering the UK solar energy market since 2023. He researches every battery and inverter brand against manufacturer datasheets, MCS and Ofgem data, and feedback from the MCS-certified installers in our directory before publishing.