Guide
LiFePO4 vs AGM vs lead-acid
Sticker price is misleading. What matters off-grid is usable capacity and how many times you can cycle it. On cost per usable kWh over its life, lithium usually wins by a wide margin.
The numbers that matter
| Metric | LiFePO4 (lithium) | AGM | Flooded lead-acid |
|---|---|---|---|
| Usable depth of discharge | ~80–100% | ~50% | ~50% |
| Typical cycle life | ~3,000–5,000 | ~400–600 | ~300–500 |
| Weight (per usable kWh) | Lightest | Heavy | Heaviest |
| Charge speed | Fast, high current | Slower | Slowest |
| Maintenance | None | None | Water top-ups, venting |
| Upfront $ / nameplate kWh | Highest | Medium | Lowest |
| Effective $ / usable kWh over life | Lowest | High | High |
Why "usable" changes everything
A 100Ah AGM battery only gives you ~50Ah before you damage it. A 100Ah LiFePO4 gives ~80–100Ah. So to get the same usable capacity you often need roughly twice the lead-acid nameplate — double the weight and space. Then lead-acid wears out in a fraction of the cycles.
When lead-acid still makes sense
- Tight upfront budget and low cycle count (occasional/backup use).
- Very cold environments without battery heating (LiFePO4 shouldn't charge below freezing without protection).
- You already own it.
For nearly every full-time van, RV or cabin build, LiFePO4 is the default in 2026.
See the size difference
Toggle battery type in the calculator — watch the required amp-hours jump for lead-acid.
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