Many inverters in a solar power system perform the same task, which is to change direct current (DC) into alternating current (AC) for use by AC appliances and gadgets.

Inverters come in all shapes and sizes.

A 1000 watt inverter uses how many amps, though? Is your inverter big enough to handle the system amp demands? Or is a bigger system required?

Depending on the inverter efficiency, a 1000 watt load on a 1000 watt 12V inverter consumes 100 to 110 amps.

The same 1000 watt load will use 40 to 60 amps on a 24V system.

How to Calculate the Amp Draw of a 1000W Inverter

Until a load is connected to an inverter, it does not use amps.

Utilize the following formula to determine the amps:

Watt load / input voltage / inverter efficiency rating = amps drawn

It would look like this if you had a 400W blender at 12V and a 1000W inverter with an efficiency rating of 85%:

400W / 12V / .85 = 39.2 amps

The blender will use 40 amps per hour, or 39.2 amps, rounded up.

Since running the blender for an hour is obviously implausible, the real amp demand will be smaller.

But it’s simple to estimate the amp needs by beginning with 40 amps per hour (20 amps for 30 minutes, 10 amps for 15 minutes etc.).

The following conversion is often used when estimating the needs for solar panels on appliances:

Watts / volts = amps

And it’s effective.

That does not, however, take into consideration inverter inefficiency, which results in energy loss and increased amp draws.

Let’s stick with the previous illustration.

400W x 12V x.85 equals 39.2 amps

If we ignore the efficiency rating of 85%, the outcome will be:

400W at 12V equals 33 amps.

That is nearly 7 amps of difference.

Is that relevant? Every amp counts if you use your 1000W inverter to its maximum capacity.

But it won’t matter if you don’t if you don’t.

Do You Need a 1000W Inverter?

Consider upgrading to a 1500W inverter, such as the Energizer 1500W, if you often load the system with 1000 watts.

Instead of pushing the load to its limit, it is preferable to have some extra power on hand in case you need to operate appliances.

The inverter should never be overworked, just like batteries.

When the load is close to 1000 watts, the overload indicator may blink even if it is not technically overloaded.

A 1000 watt inverter can theoretically power a 1000 watt load.

However, doing so often may harm the system.

Never, unless necessary, should batteries, solar panels, or charge controllers be overtaxed.

A load on your inverter of no more than 50% or 70% is acceptable with an efficiency of 80%.

The inverter can easily manage the load of a 400W blender, a 100W laptop, and a few light bulbs.

While a laptop may be used for hours at a time, most kitchen gadgets are only utilized for brief periods of time.

Keep in mind that appliance power recommendation tables are for watts per hour when estimating the number of amps that will be required.

A coffee maker uses 900 watts an hour, but after a few minutes, it won’t come close to that amount.

However, 900W of overall load is pushing it to its maximum.

And do not be shocked if a 1000W inverter cannot power your 1000 watt load.

Why? due to inefficiency and energy loss, which we shall discuss in more detail below.

Rating for Inverter Efficiency

Knowing an appliance’s efficiency rating is essential if you wish to power it – be it a refrigerator or another appliance—with an inverter.

80 percent is the minimum allowable inverter efficiency rating, however 85 percent is obviously preferable.

Although they are more expensive, some inverters have an efficiency of 90% to 95%.

Does the difference in efficiency of 5% to 10% matter? It does in the long term.

Although a 1000W inverter may theoretically load 1000 watts, in practice the load limit may only be 900W or such.

Inverter inefficiency has an impact on both amp draws and watts load.

The difference is less the higher the efficiency rating.

However, while calculating system losses, you must take the whole system into consideration.

Even if your inverter is 95 percent efficient, 5 percent of solar energy will still be wasted.

During transmission, solar cables and wires lose energy.

Additionally, the efficiency of solar panels varies, and output is weather-dependent.

You shouldn’t let this stop you from utilizing inverters, however.

It only implies that you should allow for some flexibility when estimating how many amps a gadget may use.

You can determine the size of the inverter you require by adding the total watt load and the efficiency rating.

For A 1000W Inverter, How Many Batteries Will I Need?

Appliances can only operate as long as there is electricity in the batteries since inverters use power from them to do so.

A 100ah battery with a 50% depth of discharge can power a 1000W inverter for 45 to 55 minutes while driving a 700W load.

The running duration will be greater if your battery permits a higher discharge rate of 30%.

Once again, the effectiveness of the inverter and the solar power system overall will affect the run time.

The amount of hours you need to operate the load constantly determines how many batteries you need.

Runtime x watts equals watts/volts equals required battery amps

You are using a 700 watt load with a 1000 watt 12 volt inverter.

700 watts divided by 12 volts equals 58.3 amps/hour.

To calculate run time, divide the amps per hour by the battery.

A 100ah battery will last for 1.71 hours, or 1 and 45 minutes more or less, when divided by 58.3 amps.

If the battery is entirely discharged, which you shouldn’t do, it will only last 1.7 hours.

The depth of discharge is 50% for AGM and other FLA batteries.

Thus, multiply 1.7 hours by. 50.

1.7 / .50 =3.4

That is around 45 to 55 minutes, to be exact.

Modified Wave Inverter VS. 1000W Pure Sine Inverter

If you wish to utilize an inverter, this is one of the first decisions you will need to make.

Do you choose the more expensive but better pure sine wave inverter or the less expensive but less efficient modified sine wave inverter?

Bottom line: An inverter that produces a pure sine wave, such the Renogy 1000W 12V Inverter, is a preferable option.

Although it costs more, you can be confident that it is compatible with contemporary equipment.

Modified sine wave inverters may potentially produce losses of up to 30%, which is considered undesirable by many.

For rudimentary electronics, outdated equipment, and appliances, a modified sine wave inverter is suitable.

You may utilize a modified sine inverter if the system has no sensitive components.

However, modern appliances operate more effectively on pure sine waves.

Being energy efficient is key when using solar electricity, thus pure sine makes sense.

The following appliances and pieces of equipment cannot be powered by modified sine wave inverters.

For these, pure sine is required.

  • Medical supplies
  • Home auto systems X 10
  • Any device that has a microprocessor
  • Any device having speed controls
  • Digital timepieces
  • Electronic furnaces
  • Chargers for cordless tool batteries
  • Certain fluorescent light kinds
  • Several laptops and desktops
  • Almost anything SCR (silicone controlled rectifier)
  • Anything that makes use of the electrical component thyristor

These are just a few of the gadgets and appliances that won’t work with an inverter that produces modified sine waves.

To make sure they are compatible, you need first verify your appliance.

New gadgets and appliances work with pure sine inverters, of that you may be sure.

Cost is the main barrier for most individuals.

But you should think of this as a solar panel system investment.

Additionally, replacing your equipment due to their incompatibility with modified sine wave is less expensive than purchasing a pure sine inverter.

Advice on Purchasing a 1000W Inverter

  • Get the appropriate inverter type. A 1000 watt inverter is not created equal. For the same wattage, a 95 percent efficient inverter will perform better than an 80 percent efficient unit. The performance of a pure sine wave is superior to that of a modified sine wave, of course.
  • Warranty. Along with the charge controller, inverters are the solar system’s most delicate component. For this reason, you should purchase one from a reputable manufacturer who also offers a thorough warranty coverage.
  • Usage. Determine the amps and watts you will be loading into the inverter. Use the above table as a reference to determine if 1000 watts will be enough. Consider your long-term goals and if you may need a larger inverter.
  • Size of the battery. An inverter can only function as long as the battery bank has electricity, as was previously mentioned. Take note of the depth discharge and decide if lead acid or lithium ion batteries are required. The longer your inverter can operate, the better the DOD.


Getting a precise number is challenging due to the system’s intrinsic energy losses.

However, you may get a very good idea of how many amps a 1000 watt inverter will use using the method given here.

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Written by Bob Matsuoka
Bob Matsuoka is a blogger and founder of RVing Beginner blog. He has been blogging for over five years, writing about his own family’s RV adventures, tips for people who are interested in buying an RV or taking their family on an adventure by RV.