How Many Solar Panels Do I Need For a 3000 Watt Inverter?

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If you need to run a lot of AC powered loads, a 3000 watt inverter can get the job done. These have become more affordable lately, but how many solar panels would you need to run a full power load?

A 3000 watt inverter needs twelve 300 watt solar panels to run at maximum capacity. Ten of these solar panels can produce 3000 watts, but if the weather isn’t favorable output will drop, so 12 panels is recommended.

How to Calculate 300W Inverter Solar Panel Requirements

The calculation looks simple enough. If your inverter needs 3000 watts, get ten 300 watt solar panels. 10 x 300 = 3000 watts an hour right? Well it is not that simple.

A 300 watt solar panel kit – we highly recommend the Renogy 300W Solar Kit – can yield up to 300 watts an hour. But this assumes perfect weather conditions, the sun is out and no clouds the entire day.

Even in ideal weather, a 300 watt solar panel might reach 300 watt hours only for a couple of hours at noon. After that the output drops down. So it is best to have extra solar panels available.

The calculation formula is:

Inverter watt load x runtime + 10% = solar panel size

In the following section we will explain why 10 x 300W solar panels may not be enough for a 3000 watt inverter.

How Many Solar Panels Do You Really Need?

As pointed out earlier, solar panels usually reach peak output for just a few hours a day. So a 300 watt solar panel might average 280-290 watts over five sun hours.

We are using five sun hours in this example. Check in your area how many sunlight hours are available.

10 x 300W solar panels with an average output of 290 watts each.

290 x 10 = 2900

The array only produces 2900 watts, which is short of the 3000 watts needed by the inverter.

This also does not account for inverter efficiency. A modern inverter is 90% – 95% will loses a few watts during the DC to AC conversion process. So that maximum power load will consume more than 3000 watts.

But if you had a 12 x 300 watt solar array instead of 10:

290 x 12 = 3480

A 12 x 300W solar array can give you 3480 watts an hour. Even if the solar panels never reach 300 watts, the output is still higher than the inverter requirement.

Even if your inverter is 90% efficient, there is still enough power to meet the demand. Of course you will want an inverter and PV array that is as efficient as possible for the best results.

How to Calculate Other Inverter Power Requirements

The examples assume the inverter is going to run a full 3000 watt load every hour. In that case you do need a 12 x 300W solar array to ensure ample supply..

But you won’t need that much solar power if the inverter is not going to carry a full load. In fact many users do not like to use their inverter to the limit.

Imagine you have a 2500 watt load that needs to run for four hours. How many solar panels will you need?

Inverter watt load / solar panel watt output + 10% = solar panel array

In this example we will use a 300 watt solar panel:

2500 / 300 = 8.3

8 x 300 watts = 2400 watts. Add 10% and you get 2640 watts.

Round that figure off to 2700 watts. 9 x 300 = 2700.

A 9 x 300 watt solar array can run a 2500W inverter load, even with energy losses factored in.

How Long Will a 3000W Inverter Run on Solar Power?

A 3000 watt inverter either runs on or off the grid. If it is on the grid, the inverter will keep running as long as there is grid power. An off grid inverter runs as long as there is a power source available.

If your home is tied to the grid, only a power outage can stop it from running. If the solar panels cannot generate the required energy, the system will use grid power.

A 3000 watt off grid inverter can run directly off solar panels , but there are limitations. The inverter can only operate during daylight and if there is enough power to carry the load.

For example, the inverter is carrying a 2400 watt load. There are five sun hours in your area. Theoretically the inverter can run solely on the PV array for five hours.

But this assumes the array generates at least 2400 watts. If the output drops below that, the system will not be able to work properly.

Even if there is sunlight, the panels must still produce enough power to maintain the power load. This is why we recommend installing a large solar array so the system can produce more power.

These problems can also be avoided if you have a battery bank. In fact, all large off grid solar systems should have one.

What Batteries Do I Need For a 3000W Inverter?

Solar power systems have many battery options, but it comes down to two main types, lead acid and lithium. Lead acid battery comes in two types, FLA (flooded lead acid) and SLA (sealed).

The most widely used solar batteries are lithium and SLA. SLA comes in two forms, gel and AGM. Lithium batteries provide the longest lifespan and ideal for heavy duty work. The Ampere Time 300ah LiFePO4 12V battery will have no problems running a 3000 watt inverter.

The biggest difference between FLA and SLA batteries is depth of discharge and maintenance. AGM and gel do not need as much maintenance as FLA, which is always a plus.

Lead acid batteries have a 50% depth of discharge. That is, you are supposed to recharge the battery when the power hits 50%. With high end AGM and gel batteries, the DOD can be up to 70%.

Ideally you should recharge SLA batteries at 50% also, but it will not damage the battery if the DOD goes down to 70%.

The DOD for lithium batteries is 70% minimum and up to 100%. There is no maintenance required either. The charge and recharge times are faster, but again this comes at a higher price tag.

For more information on what battery size is best for a 3000 watt inverter, check this guide. But what it comes down to is you have to calculate how much power you want to run from battery power and for how long.

For most people, AGM batteries are the best option. It is right between the maintenance heavy lead acid batteries and expensive lithium. Of course if budget is not an issue you should get a lithium battery bank. But for many, AGM batteries are enough.

Do You Even Need Solar Panels?

You can run inverters off solar panels, but are they necessary? The answer is no, but solar panels offer many benefits.

If your home is tied to the grid, you can run the inverter off the main power supply. You don’t need solar panels or even batteries.

Grid tied solar systems shut down during a power outage for safety reasons. If you want access to solar power during a blackout, you need a battery bank or solar array. You can also use them together. For instance you can charge the batteries with the solar panels and use the batteries to power the inverter.

If you are off grid, you can run the inverter entirely from a battery bank. Of course the batteries must have enough power to run the inverter.

You need a 300ah battery minimum to start the inverter, and that will run the system for an hour only. You need another battery or solar array to recharge it. In the meantime you must have another power source to keep the inverter going.

The point is, you can use an inverter without solar panels. But there are many reasons why you should. For one, it is an effective battery charger. Second, it is cheaper in the long run to use a solar array than keep paying monthly energy bills. Off grid systems can also use a combination of solar panels, batteries and even a generator to power inverters.


A 3000 watt inverter can run several appliances, but it is only as effective as its energy source. A combination of at least 12 x 300 watt solar panels and a large battery bank will suffice. With this you can expect your appliances to run smoothly.