How many amps is 1000 watts at 12 volts?
1000 watts at 12 volts is 83.3 A. If that is an AC load on an inverter, the 12 V battery supplies about 92.6 A once a 90% inverter takes its share.
How to work it out
- 1,000 W ÷ 12 V = 83.3 A
- Through a 90% inverter: 1,000 W ÷ 0.9 = 1,111 W from the battery ÷ 12 V = 92.6 A
This is the question behind most 12 V inverter purchases: a 1000 W microwave, coffee maker or hair dryer on a van or RV battery. The plain conversion is simple; the inverter loss is what people forget.
Adjust for your project
More options: Inverter eff.
- Battery current through the inverter
- 92.6 A
- Energy per hour of running
- 1 kWh
| Voltage | Amps | Battery amps at 90% |
|---|---|---|
| 12 V | 83.3 A | 92.6 A |
| 24 V | 41.7 A | 46.3 A |
| 48 V | 20.8 A | 23.1 A |
| 120 V | 8.3 A | — |
| 240 V | 4.2 A | — |
Amps for common loads at the voltage above
| Power | Current | Battery current through the inverter |
|---|---|---|
| 100 | 8.3 A | 9.3 A |
| 300 | 25 A | 27.8 A |
| 500 | 41.7 A | 46.3 A |
| 1000 | 83.3 A | 92.6 A |
| 1500 | 125 A | 138.9 A |
| 2000 | 166.7 A | 185.2 A |
| 3000 | 250 A | 277.8 A |
What 92 amps means for a 12 V system
- A 100 Ah battery lasts under an hour at this rate. At about 92.6 A from a 12 V system, a 100 Ah LiFePO4 battery used to 80% runs it for under an hour — see how long a 100Ah battery lasts with a 1000W inverter.
- Check the battery’s discharge limit. Victron recommends no more than 100 A continuous (200 A maximum) from its 12.8 V 100 Ah LiFePO4. A 1000 W load sits close to that; a bigger inverter needs two or more batteries in parallel just for current.
- Lead-acid gives less at high current. Trojan’s group 27 data sheet shows 105 Ah at the 20-hour rate but only 85 Ah at the 5-hour rate — and at 92 A it empties far faster than that.
- Short, heavy cables. At this current, cable length and size matter a great deal. Wire and fuse sizes come from NEC/ABYC ampacity tables and the equipment manual — have a qualified installer check them.
At 24 V the same 1000 W is about 46 A through the inverter, and at 48 V about 23 A — which is why larger systems step up the voltage. The inverter side is on how many amps a 1000 watt inverter draws.
Different size? Use the full Watts to Amps Calculator.
What you’ll need
- DC clamp meterMid-range price
Clamps around one cable to read DC amps without breaking the circuit — checks what an inverter or fridge actually draws from the battery. Make sure it says DC; many cheap clamps read AC only.
See options on Amazon (opens in a new tab) - Pure sine wave inverter, 1000 WMid-range price
Enough for a CPAP, laptop, TV and small appliances. Pure sine is the safe choice for anything with a motor or sensitive electronics.
See options on Amazon (opens in a new tab) - 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)
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
How many amps is 1000 watts at 120 volts?
8.3 A — one-tenth of the 12 V figure.
How many amps is 1000 watts at 24 volts through an inverter?
41.7 A before losses, about 46.3 A from a 24 V battery through a 90% inverter.
How many amps is 1000 watts at 48 volts?
20.8 A.
Other common sizes
- How many amps is 1500 watts at 120 volts — 12.5 A
- 400 watts to amps at 12V — 33.3 A
Sources
- Virginia Cooperative Extension, BSE-301: Estimating Appliance and Home Electronic Energy Use (2020) (opens in a new tab) — Wattage × hours ÷ 1,000 = kWh per day; watts = amps × volts when only amps are listed; a refrigerator runs at full wattage about a third of the time; typical nameplate wattages.
- 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%.
- Victron Energy — Which solar charge controller: PWM or MPPT? (2020) (opens in a new tab) — MPPT output current = panel watts ÷ battery voltage (100 W ÷ 13 V = 7.7 A); a PWM controller pulls the panel down to battery voltage (81 W from a 100 W panel at 25 °C, about the same as MPPT at 75 °C); temperature-coefficient method; example panel Voc 21.6 V, −0.35 %/°C.