LiFePO4 vs Lead-Acid: Why Lithium Has Already Won

Ten years ago, lead-acid AGM/gel batteries were the only adequate choice for home solar. In 2026, LiFePO4 (lithium iron phosphate) has beaten them on every metric except purchase price. Here's why. Cycle life. AGM lasts 500–800 cycles to 50% remaining capacity. LiFePO4 — 4,000–6,000 cycles. At typical use (1 cycle/day) AGM lasts 2–3 years, LiFePO4 — 12–16 years. Depth of discharge. AGM should not be discharged below 50%, otherwise lifespan drops sharply. So out of nominal 200 Ah, only 100 is usable. LiFePO4 happily discharges to 90–95% — 180–190 Ah usable out of 200. Efficiency. AGM — 80–85% (heat and self-discharge losses). LiFePO4 — 95–98%. So out of every 100 kWh you put in, you get 95 back vs 82. Maintenance. AGM must be kept above freezing (or capacity collapses), not tipped, terminals checked periodically. LiFePO4 — install and forget. Works from -20°C to +60°C (with heating — to -30°C). Real lifetime cost per kWh. AGM 200 Ah (12V) ≈ UAH 12,000 with 1.2 kWh usable capacity × 600 cycles = UAH 16.7/kWh. LiFePO4 12V 200 Ah ≈ UAH 24,000 with 2.4 kWh × 5,000 cycles = UAH 2/kWh. Eightfold difference. Bottom line. If you have a site with cyclical battery use (solar plant, dacha with outages) — go LiFePO4 only. If it's a backup for 1–2 events per year, AGM still makes sense, but that's the last frontier.