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There is no question that a 3000 watt inverter packs a lot of power, but how long will it last? Can it run a conventional refrigerator? What about a microwave? And how many appliances can the system run before losing power?
A 3000 watt inverter can run a few lights, a laptop, phone charger, a 40 inch TV and a fan simultaneously for 7 to 8 hours. The runtime will always depend on the watts drawn per hour and the battery capacity available.
Calculate How Long a 3000 Watt Inverter Will Last
Add the total appliance watt hours, divide by the inverter capacity and multiply by the inverter efficiency rating. The result is the runtime. No matter what the inverter size is, the calculation formula is the same.
If you have a 3000 watt, 90% efficient inverter and its appliance power load is 1250 watts, the formula looks like this:
3000 / 1250 = 2.4
2.4 x .90 = 2.16
A 3000 watt inverter can run a 1250 load for 2.16 hours before running out of battery power. This calculation makes the assumption there is enough battery capacity available to run the load.
A quality 3000 watt inverter like the Renogy Pure Sine Wave should be able to run a 3000 watt load for an hour. Depending on what on other appliances are running, it might last longer. This is why it is important that you use the right inverter size for your solar system.
But due to the way inverters work, it is not 100% effective no matter the inverter brand. The good news is inverters are getting better all the time and inefficiency ratings are dropping.
In the meantime you should always include the efficiency rating in your calculations. Doing so gives you a more realistic approximation of the runtime and avoid pushing the system to the limit.
Inverter Runtime Chart
This table gives you an example of the inverter runtime while running various appliances. These figures are estimates only. The runtime will differ depending on the number of appliances you run at the same time and their specs. Add the different efficiency ratings and it is easy to see why inverter runtime estimates are just that, estimates.
|Power Load||Estimated Inverter Runtime|
|14 cu. ft. refrigerator||2 hours|
|Laptop, fan, a few lights||12+ hours|
|40 inch TV and fan||20+ hours|
|Washing machine||2+ hours|
|Window AC||1-2 hours|
|Gaming computer||3.5 hours|
|TV with Blu-Ray player||20+ hours|
To get a more accurate figure, list the power consumption specs for each appliance you will load. Then note how long you actually run them. For instance, use your laptop as you normally would, along with any other essential appliances or devices you want to run with it.
You will have an idea of how many watts or amps you use. Now you can use these figures to determine how many batteries you will need for the inverter.
When you have the right numbers, it is easy to set up the rest of the system. This is crucial for any solar system, whether it is on or of the grid.
What Will a 3000 Watt Inverter Run?
An inverter can run any number of electrical load within its capacity. in this case the capacity would be just under 3000 watts, depending on its efficiency rating.
The following are common appliances and their watts / amps usage. Add the total watts per hour and you should have an idea of how long the inverter can run. You can also add the amps instead. Doing so gives you a good estimate of how much battery power the load will require.
|Fan||35-50||Less than 0.5|
|Radio||40||Less than 0.5|
|Lights||60||Less than 0.5|
|Phone charger||12||Less than 0.5|
|Blu-Ray player||40||Less than 0.5|
|42 inch TV||120||Less than 0.5|
|Laptop||120||Less than 0.5|
The power consumption figures given here are general approximations. There are different types of microwaves, lights, television sets and toasters for instance, and some will consume more power than others. Check the power consumption on each appliance label to get a more accurate figure.
For example, a 42 inch TV typically consumes 120 watts. You can run it along with a few lights and a fan for several hours. But if it was a 75 inch TV and a whole house fan, the runtime will be shorter. The same applies to the other appliances in this chart. A typical desktop computer uses 200 to 300 watts. A gaming system however, can go up to 800 watts.
Once you know the total appliance wattage, it is easy to figure out how much battery power you will need and how long the inverter can run.
How Many Batteries For a 3000 Watt Inverter?
A 3000 watt inverter needs a 500ah battery bank to run at full power. The more battery power available, the longer the inverter can keep running its load.
An inverter is only as powerful as the batteries connected to it. In a solar system, the battery bank serves as the main power source, working along with the solar panels.
If the battery has a better discharge rate you can adjust the usage. Some AGM batteries for example, are rated at 70%. Lithium batteries can be fully discharged so you can use its power up completely. Check the battery specs first.
A 12V 250ah deep cycle battery holds 3000 watts. There are many options but our favorite is the Mighty Max 250 as it plenty of power. But you should not drain lead acid batteries by more than 50%, so only 1500 watts are usable. To get the full 3000 watts, 500ah is required so even if it s recharged at 50% there is sufficient power available.
But that is only the start. The real question is, how many watts is the load and how long do you need to run it on the inverter? To figure it out, you have to add the total watts to be used by all the appliances and how long you will need them.
Battery Inverter Size Calculation Example
Assume you have several appliances totaling 1300 watts and you want to run them for four hours on a 3000 watt inverter. How many batteries will you need?
1300 watts x 4 hours = 5200 watts
Now we convert 5200 watts into amps. Assuming you will be using 12V batteries:
5200 / 12 = 433.3 amps
Round off 433.3 to the nearest battery size available, and you need 500 usable amps to run a 1300 watt load for four hours. Note that we say usable amps, not battery size. Remember that FLA batteries must not be discharged below 50%, so a 500ah battery only has 250ah available. You must get a 1000ah battery bank to run this load.
A simple solution would be to use 24V batteries. Using the same calculations above, the results are going to be different:
5200 / 24 = 216
Even if you double the battery size to make up for the 50% discharge, you will only need a 500ah 24V battery bank instead of 1000ah. This is the reason why many inverters are compatible with 24V batteries because they are more practical to use.
In fact several inverters are optimized to run with 24V systems. That is not going to be an issue since 24V batteries are widely available. And if you only have 12V batteries, you can connect them in a series to increase the voltage.
As for battery type there is no shortage of options. The most popular are deep cycle batteries like FLA, AGM and gel. Lithium ion are also becoming more common, though their price tag is still higher than FLA.
Tips For Running a 3000 Watt Inverter
While these inverters are very capable, you should plan its use carefully to get the best possible results. Here are some suggestions.
- Limit the appliances you run at the same time. By reducing the load, the inverter will have more power available to run for longer periods.
- Combine solar panels with batteries. Solar panels can run power loads during the day, so you only need to use the batteries at night.
- Keep the wiring as short as possible. The shorter the wiring distance between the inverter and batteries, the less energy will be lost.
- Invest in a quality inverter. You will be running appliances through this system, so make sure it is well designed and can handle the load.
- Leave room for more power. Overestimate the amount of power you need to use. Is 3000 watts really enough or will you need more? Do not be conservative with your numbers.
Ask any electrician and they will tell you it is never a good idea to load a power outlet to its limit. The same applies to inverters and batteries. Fortunately these devices have built-in safety mechanisms for protection against possible overloading.
Do not run the inverter at its limit. This is especially important for AC units that use a lot of solar power and also refrigerators, toasters, microwaves and other high powered devices..
Even though the system can load 3000 watts (more or less), you should avoid doing this except for short bursts. For instance, a fridge that requires a 3000 watt surge to start up is acceptable since it is only for a second.
A 3000 watt inverter carries a lot of capacity, so no wonder it is found in RVs, boats and homes. The key to using it – and any type of solar power system – is to manage the appliance load and ensure the system is not overloaded.
I am an advocate of solar power. Through portablesolarexpert.com I want to share with all of you what I have learned and cotinue to learn about renewable energy.