Lead Acid AGM vs Lithium Cost Comparison
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At first glance, AGM lead-acid batteries might seem like the more budget-friendly choice. A 12V 100Ah AGM battery costs around $170, while a lithium battery of the same capacity costs $190. That $20 difference may look appealing, but there’s more to the story.
Since lead-acid batteries can only use 50% of their capacity without risking damage, you’d actually need two AGM batteries to match the usable capacity of a single lithium battery. This brings the upfront cost of lead-acid to $340, making lithium the cheaper option for usable energy right out of the gate.
Efficiency further tips the scale in favor of lithium. Lead-acid batteries are about 80% efficient, meaning you lose some energy during charging and discharging. When you adjust for this inefficiency, the real cost of lead-acid rises to $425. Lithium batteries, with a much higher efficiency of 92%, come out to just $206 for the same usable power. Already, lithium is less than half the cost of lead-acid when you account for efficiency.
Then there’s the matter of lifespan. Lead-acid batteries typically last for about 1,000 cycles at 50% depth of discharge, while lithium batteries can handle up to 4,000 cycles at 100% depth of discharge. To match the performance of a single lithium battery over its 4,000-cycle lifespan, you’d need four sets of lead-acid batteries, costing $1,700 compared to just $206 for lithium. Over time, that makes lead-acid batteries eight times more expensive.
In real-world use, lithium batteries are even more practical. Though their battery management system (BMS) may limit their lifespan to around 10 years, they’ll still retain about 90% of their original capacity after daily cycling. Meanwhile, lead-acid batteries will need multiple replacements over the same period, further increasing their long-term costs. Even if you assume less-than-ideal conditions, lithium remains the clear winner in cost, durability, and performance.
Of course, there are some situations where lead-acid still makes sense. For example, lead-acid batteries can charge directly from an alternator, making them simpler and cheaper for certain setups. They’re also a solid choice for backup systems that aren’t cycled often, and they can charge in freezing temperatures where lithium batteries require additional heating.
But for most applications, especially in solar, or off-grid setups, lithium’s superior efficiency, longer lifespan, and lower long-term cost make it the smarter investment.