How Long Will a 100Ah Battery Run a 200W Load?

Short answer: 3.5 to 5.5 hours, depending on whether you’re using an inverter or powering directly from DC.

A 12.8V 100Ah LiFePO4 battery holds about 1,280 Wh of energy. With 90% usable capacity (that’s typical for LiFePO4), you get roughly 1,150 Wh to work with.

At 200W continuous draw:

• DC power (no inverter): around 5–5.5 hours
• AC through an inverter: around 3.5–4 hours

The difference? Inverters eat up 10–20% of your energy through conversion losses, plus they draw 5–15W just sitting there. At 200W, that’s enough to cost you over an hour of runtime.

What Counts as a 200W Load?

Think of 200W as a medium-sized workload — not a single appliance, but often a combination: a TV with a soundbar, a desktop computer with monitor, or networking gear with some accessories running alongside.

Keep in mind: if your device has a motor or compressor (like a mini fridge), startup surges can briefly pull 3–5x the rated power. Your battery can handle it, but it affects overall runtime.

DC vs AC: When It Matters

Most home appliances need AC, so you’ll use an inverter. That’s fine — just expect the shorter runtime.

But if you’re running an off-grid setup, RV, or backup system, check if you can power things directly from DC. Networking equipment, mini PCs, and many 12V appliances skip the inverter entirely. That extra hour of runtime can make a real difference during an outage.

What About Lead-Acid Batteries?

Here’s where the “100Ah” label gets misleading.

Lead-acid and AGM batteries shouldn’t be drained below 50% if you want them to last. So your “100Ah” lead-acid battery really gives you about 600 Wh usable — roughly half of what LiFePO4 delivers.

Same battery capacity on paper, very different results in practice:

• LiFePO4: ~5 hours at 200W (DC)
• Lead-acid: ~2.5–3 hours at 200W (DC)

Calculate Your Exact Runtime

Plug in your actual battery specs and load — especially useful if you’re running something other than exactly 200W, or using a different battery chemistry.

Bottom Line

A 100Ah battery handles a 200W load comfortably for several hours. The biggest variable is whether you’re going through an inverter or not.

If you can run DC, do it. You’ll get noticeably more runtime from the same battery.

For a deeper dive into battery runtime calculations, check out the main guide:

How Long Will a 100Ah Battery Last?

Last updated: December 2025