Lead-acid batteries lose 15-20% of energy during charge and discharge. Lithium loses only 5%. That gap is huge. It means more of your solar power actually gets used. Lithium also lasts 3 to 5 times longer. You replace them less often. That saves money and waste. They are lighter too. A lithium battery weighs half as much as lead-acid for the same power. And lithium handles deeper discharge. You can drain it to 80% without damage. Lead-acid dies fast below 50%. The upfront cost of lithium is higher. But over ten years, lithium is cheaper. You get more cycles. More usable energy. Less hassle. Solar installers are switching fast. Homeowners are noticing. The old lead-acid days are fading.