What Will a 1200W Inverter Run?

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If you want to use AC appliances with solar power, an inverter will be required. 1200 watt inverters are quite popular in homes, RVs and off grid systems, but is it enough to run your favorite appliances?

A 1200 watt inverter can run a TV, lights, a small microwave, laptop and other appliances. The inverter can run any appliance as long as the power consumption is under 1200 watts.

How to Calculate 1200 Watt Inverter Capacity

Figuring out how many appliances a 1200W inverter can run depends on several factors. We will go over the most important ones and how it affects capacity.

A 1200 watt inverter requires more than 1200 watts to run at full capacity. This is because inverters use power even without a load. Assuming the inverter uses 10 watts on standby mode and is 95% efficient, a 1200 watt load will consume around 1260 watts.

A good analogy is a TV. TVs in standby mode consume a bit of energy. The only way to eliminate power consumption is to turn off standby mode.

The same rule applies to inverters. When in standby mode, a 1200 watt inverter might draw 5 to 10 watts. So if you load 1200 watts, the system will consume 1210 watts an hour.

The larger the inverter, the more watts it uses in standby mode. A 2000 watt inverter might use 15W, and larger ones around 20W or so.

You can save power by using an efficient system. The NDDI Direct 1500W Inverter is a good example of efficiency. You can run the load you want but the inverter minimizes power loss.

This is not a big issue given the convenience of having the inverter available in standby. And the power is not really wasted since the inverter is using it.

If you really want to conserve power, just turn off standby mode. However it is better to leave it open especially if you constantly use the system.

Inverters are also getting better and better. A large inverter may use more standby power, but if you are running a large load it becomes negligible.

What Appliances Can a 1200W Inverter Power?

The inverter can run any appliance or combination of appliances provided it is under 1200 watts per hour. However there is more to it than that.

The inverter can operate a laptop, TV, food processor, movie players, coffee machine, an energy efficient fridge, microwave, lights, small power tools, fans etc.

Basically any appliance that uses less than 1200 watts will work. You cannot run these all at the same time, but the actual usage varies from person to person.

These appliances also have variable usage times so that needs to be factored. A microwave might be 700 watts, but it will only consume that amount if it runs for an hour. If you just use it for a few seconds to reheat food, wattage consumption will be lower.

So when totaling RV power usage for example , think of how long you actually use the appliances. You might be surprised at how many you can use with a 1200W inverter.

If you are always loading the inverter at full capacity, consider replacing it with a 1500W or 2000W system.

While you can run an inverter to full capacity, it is better to have reserve power available. Power surges can happen, or you might need to plug in another device in an emergency.

Large inverters are more efficient when running a large load, but not at full capacity. A 1200W inverter runs best when the load is 900 to 1100W.

Inverters that are always running at full capacity leads to faster wear and tear. And in case there is a sudden power spike it will overload the system. This is why you need to have reserve power at all times.

What is Inverter Running and Surge Wattage?

Running wattage is what an appliance uses as it runs. Surge or starting watts is what the appliance needs to start up.

Inverter ratings are usually in running watts. So a 1200 watt inverter means the system can load 1200 watts an hour. The surge watt capacity is usually twice that, so 2400 watts in this case.

Inverters can only supply the surge watts for a few seconds. When looking at appliance wattage, make sure you account for both running and surge watts.

For example, a portable AC unit might need 1000 running watts but 2500 watts to start up. In that case a 1200 watt inverter is not enough. Its running watt capacity is sufficient but the surge watts is not.

Almost all inverter surge watt capacity is twice its running watts. But just to be sure you should refer to your operating manual.

You should also do the same with appliances. While most appliance surge watts is also twice the running watts, sometimes it is three times higher. Check the appliance power usage before plugging it into the inverter.

How Inverter Efficiency Affects Load Capacity

Inverter efficiency is the amount of energy lost when direct current is converted into alternating current. The lowest acceptable rate is 85%.

Unlike standby mode usage, inefficiency results in actual power losses. This also adds to the watts used by an inverter.

Inverter watt capacity x inverter inefficiency = additional watts used

If you have a 1200W inverter with an 85% efficiency rating, the system will use 1380 watts.

1200 x 15% = 180

1200 + 180 = 1380

If you have a 1200W inverter with a 93% rating:

1200 x 7% = 84

1200 + 84 = 1284

The same load will use 1284 watts an hour, a difference of almost 100 watts.

What if you are not running a full load? Multiply the running load, not the inverter size.

If a 1200W, 90% inverter has an 800W load, the calculation is:

800 x 10% = 80

800 + 80 = 880

The inverter consumes 880 watts an hour.

What these numbers show is that efficiency is very important. The difference between an 85% and 93% efficiency is almost 100 watts an hour, so invest in a high efficiency system.

How Long Will a 1200 Watt Inverter Last?

Inverter runtime depends on two factors: how many watts it is running and how much energy remains from its power source.

If the inverter is running a full load it will last for an hour, give or a take a few minutes. If the load is 600 watts, the runtime is approximately two hours.

Inverter size / running load = runtime

So if your inverter has a 500 watt load, it will run for about two and a half hours.

1200 / 500 = 2.4

This running time is only an estimate. Its efficiency rating will determine how many watts it consumes. A low efficiency inverter will draw more watts or amps from the battery. This will lead to faster battery depletion and shorten the runtime.

Batteries also discharge faster when more amps are drawn. The UPG 100ah 12V battery should hold 1200 watts and last for an hour. But in reality the runtime might be less than that.

Batteries are rated at 5 amp draws per 20 hours. That is, if 5 amps are drawn per hour, the battery is good for 20 hours. But if 10 amps are pulled, that does not mean 10 hours. It could be just under 10 hours.

This has nothing to do with product defects, it is just how batteries work. So in our case if the inverter is running at 1200 watts an hour, it needs to draw 100 amps.

The battery probably won’t even be able to supply 100 amps. At some point when the amps are too low the battery will stop working. You cannot use the full capacity from a regular deep cycle battery unless it is lithium, which can handle a full discharge.

If you want to get maximum battery power, double the battery capacity. if you need 1200 watts from the battery bank, get a 12V 200ah system. This will also allow you to recharge the batteries at the 50% depth of discharge rate.


There are many types of inverters, so two models with a similar capacity will not necessarily perform at the same level. This is why you need to be do some research to determine if it is right for your requirements.