What size battery bank for a 3000W inverter?
To run a 3000W inverter at full load for one hour on 12 V, you need about 326 Ah of LiFePO4 — 4 × 100 Ah 12.8 V in parallel. The battery current is about 260 A.
How to work it out
- 3,000 W ÷ 90% × 1 h = 3,333 Wh
- 3,333 Wh ÷ 80% usable ÷ 12.8 V = 326 Ah = 326 Ah
- 326 Ah ÷ 100 Ah per battery → 4 × 100 Ah 12.8 V in parallel
A 3000 W inverter is the size that runs a microwave, a coffee maker and a hair dryer — though rarely all at once. At 12 V it is also where the current becomes the real design problem.
Adjust for your project
More options: Inverter eff. · DoD · Battery temp
- Made up of
- 4 × 100 Ah 12.8 V in parallel
- Batteries
- 4 batteries · LiFePO4
- Energy the bank must deliver
- 3,333 Wh
- Rated energy of that bank
- 5,120 Wh
- Battery current at full inverter load
- 260 A
A 3000 W load for different lengths of time (12 V LiFePO4)
| Hours at that load | Battery bank needed | Batteries | Battery current at full inverter load |
|---|---|---|---|
| 0.25 | 81 Ah | 3 batteries | 260 A |
| 0.5 | 163 Ah | 3 batteries | 260 A |
| 1 | 326 Ah | 4 batteries | 260 A |
| 2 | 651 Ah | 7 batteries | 260 A |
| 4 | 1,302 Ah | 14 batteries | 260 A |
What to know about a 3000 W inverter’s battery
- 260 A from 12.8 V. Victron recommends at most 100 A continuous from its 12.8 V 100 Ah LiFePO4, so three in parallel is the minimum for current alone, before you think about runtime.
- At 24 V it is half the current. Two strings of two 100 Ah batteries in series (24 V, 200 Ah) hold the same energy and draw about 130 A — the main reason big inverters are often 24 V or 48 V.
- Lead-acid needs far more. At 50% usable and a high discharge rate, a 12 V AGM bank for the same hour would be about 556 Ah on paper and about 800 Ah once the Peukert correction for 278 A is applied — and its voltage would still sag hard.
- Most hours aren’t full load. An inverter sized at 3,000 W often averages a few hundred watts. Size the energy from a solar load list and the current from the biggest thing you will run.
The smaller version is what size battery bank for a 2000W inverter. For the inverter’s own size and surge, see what size inverter to run a microwave.
Different size? Use the full Battery Bank Size Calculator.
What you’ll need
- 12 V 100 Ah LiFePO4 batteryPremium price
About 1.28 kWh rated in a box roughly the size of a group 24–31 lead-acid battery at around half the weight. Check the BMS discharge limit and whether it can charge below freezing.
See options on Amazon (opens in a new tab) - Pure sine wave inverter, 2000–3000 WPremium price
For microwaves, coffee makers and power tools. At 12 V these draw hundreds of amps, so the battery and cabling matter as much as the inverter.
See options on Amazon (opens in a new tab) - Battery monitor with shuntMid-range price
Counts amp-hours in and out, so you see true state of charge instead of guessing from voltage — which barely moves on a LiFePO4 battery until it is nearly empty.
See options on Amazon (opens in a new tab)
As an Amazon Associate we earn from qualifying purchases. Links to products are affiliate links — they cost you nothing extra and help keep these calculators free.
Frequently asked questions
What size battery bank for a 3000W inverter at 24 V?
About 163 Ah at 25.6 V — 4 batteries: 2 strings of 2 × 100 Ah in series — drawing 130 A.
What size lead-acid battery bank for a 3000W inverter for an hour?
About 802 Ah of 12 V AGM (9 × 100 Ah 12 V in parallel) after the Peukert correction for 278 A — against about 556 Ah on paper.
What size battery bank to run a 3000W inverter for 2 hours?
About 651 Ah of 12.8 V LiFePO4 — 7 × 100 Ah 12.8 V in parallel.
Other common sizes
- What size battery bank for a 2000W inverter — 217 Ah of 12 V LiFePO4 for an hour — 3 × 100 Ah
Sources
- Victron Energy — Lithium Battery Smart manual, technical data (opens in a new tab) — LiFePO4 12.8 V: cycle life 2,500 at 80% DoD, 3,000 at 70%, 5,000 at 50% (to 80% of capacity); 92% round-trip efficiency; 12.8 V 100 Ah: recommended continuous discharge ≤100 A (1C), maximum 200 A; capacity about 20% lower at 0 °C; charge only between +5 °C and +50 °C.
- Trojan Battery — Technical support FAQs (opens in a new tab) — “We generally recommend a discharge of 20 to 50% of the battery’s rated capacity even though the battery is capable of being cycled to 80%”; 20-hour and 100-hour ratings; freezing points by state of charge.
- Trojan Battery — 27TMX data sheet (opens in a new tab) — Group 27 flooded: 85 Ah (5-hr), 97 Ah (10-hr), 105 Ah (20-hr), 117 Ah (100-hr); state of charge vs open-circuit voltage table; charger settings.
- Crown Battery — Deep Cycle Battery Product Specifications (effective Oct 1, 2024) (opens in a new tab) — 20-hour capacities by BCI group for flooded, AGM and lithium 12 V batteries.
- Victron Energy — Energy Unlimited (book) (opens in a new tab) — Lead-acid charge efficiency 80–95% (85% suggested as a starting value); battery energy efficiency about 75% for full cycles, about 89% in partial state of charge; inverter efficiencies above 90%.