Inverter Capacity for 150ah Battery Guide

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150ah batteries are often used in off grid homes and RVs to run inverters. One of the things you have to do is make certain that the inverter is large enough, in this case for a 150ah battery. In this guide we will explain what capacity you will need.

A 12V 150ah battery can store 1800 watts so a 2000 watt inverter is the right size. A 24V 150ah battery holds up to 3600 watts, which means you should use a 4000 watt inverter.

How to Calculate Inverter Capacity

Inverter capacity is measured in watts. Battery sizes are measured in amp hours, so you need to find out how many watts a 150ah battery is.

Battery ah x battery voltage = watts

So if you have a 12V Eco Worthy LiFePO4 150ah battery, the watt capacity is 1800. With a 24V battery that would be 3600 watts. A 2000 or 4000 watt inverter would be appropriate in these instances.

You can use a smaller inverter size if you do not intend to run the battery at full capacity. If you will only load 900 watts on a 12V 150ah battery, a 1000 or 1200W inverter will do fine.

There are good reasons why you may not want to run the battery inverter at full capacity. The most important is that lead acid batteries have a depth discharge rate of 50%.

What this means is with a 150ah battery, only 75ah is usable per charge. You can use the full 150ah but it is not advisable for two reasons.

One, a full discharge is not good for battery health. It will wear the components out faster. The life cycle gets shorter and charging capacity drops.

Second, you will not get 150ah from the battery. Before it drops to 0%, the battery will stop running. Due to the inherent nature of batteries, discharge rate speeds up when more amps are pulled.

The solution is to buy another 150ah battery. With a 300ah battery bank you can run a full inverter load and not worry about the depth discharge dropping below 50%.

How Long Can a 150ah Inverter Battery Last?

There are several factors to consider here: the inverter efficiency, battery capacity, load and the prevailing conditions.

A 12V 150ah battery can run a 1800 watt inverter load for an hour. A 24V 150ah battery is going to last two hours with the same load. Both batteries will be almost 100% empty by the end.

Those are estimated running times, and there are many reasons why your battery bank may not last that long. The most important difference is the voltage. keep this in mind if you will use a 150ah battery for backup power.

A 24V battery can hold twice as many watts as a 12V. A 12V also pulls twice as many amps as a 24V, depleting the battery faster.

If you have a 24V 150ah battery, you can load almost 3600 watts into an inverter. We say almost because due to inefficiency, inverters will use more power (more on that in a bit).

If you place the same load, the 24V 150ah battery will last longer than the 12V because it draws fewer amps.

A 12V battery with a 900 watt load:

900 / 12 = 75

It pulls 75 amps an hour.

Compare that with a 24V battery:

900 / 24 = 37

The same watt load pulls only 37 amps.

This is just one of the differences between a 12V and 24V battery. Bottom line is you get more battery mileage from a 24V than 12V even if both are 150ah.

Okay, so 24V batteries are more efficient than 12V. But what if my system is designed for 12V?

Most RVs are indeed designed for 12V systems. But by connecting two 12V batteries in parallel you increase the voltage to 24V.

How Inverter Conversion Efficiency Affects Battery Runtime

Inverter ratings are based on how well they convert DC to AC power. If an inverter has a 90% rating, it means 10% energy is lost during the conversion.

This also means that inverters consume more watts than the load they carry. A 90% efficient inverter with a 1500 load consumes 1650 watts, not 1500.

If the inverter uses more watts, it also pulls out more amps. It might not be much of a difference with a small load. But for large ones this is going to have an impact.

Obviously the higher the inverter efficiency rating, the better for your system. There are two options, pure sine and modified sine wave. Pure sine wave inverters are the most effective, though some appliances also work with modified sine wave inverters. The GoWISE 2000W Power Inverter is one of the best examples of an efficient, pure sine wave inverter.

The more load you place on an inverter, the more important the efficiency is. If we are talking about hundreds or thousands of watts, the efficiency rating will make a huge difference.

What Can You Run on a 150ah Inverter Battery?

The battery will run any appliance load provided it does not exceed 1800 watts for 12 volts and 3600 watts for 24 volts. This also assumes that the inverter has sufficient capacity.

This inverter battery can run TVs, light bulbs, kitchen appliances, computers and other devices and appliances. The runtime depends on how many appliances you run at the same time.

Use this guide to check how many watts your appliances are. But for a 150ah battery, you will only use a limited number.

Assuming it is a 12V battery and good for 1800 watts, you can load a laptop, a TV, several lights, a fan and a small microwave. You can load all these and the inverter battery should last an hour.

This is just an example. You probably don’t microwave for an hour so you can load other appliances when you are done. But again, lead acid batteries are not supposed to be fully discharged.

if you want to run a full 150ah inverter load, get a lithium battery. You can discharge these 90% to 100% which is ideal if your inverter has to carry a full load. You may also combine two 150ah batteries to give you 300ah, enough to power your appliances.

The number of appliances or devices you can load depends on the battery capacity . A 150ah battery may be limited to 1800 watts (12V) or 3600 watts (24V), but if you join it with other 150ah batteries, you can run as large a load as needed. If you have four of these batteries charge by solar panels the runtime will be longer.

The only limitation is the inverter size. You also have to make sure that the charge controller can handle the extra power. You can compare this with solar panels, whereby you add more panels to improve performance.

How to Make an Inverter Battery Last Longer

There are many ways to do this, but the following are the most practical and should always be carried out.

  • Perform regular battery maintenance. This is particularly true for lead acid batteries. Refill with water when required and keep it away from heat sources.
  • Do not allow the battery to be fully discharged. For lead acid batteries, recharge at 50%. You can top it off at 85%. A full 100% charge is not advisable.
  • Do not load the inverter at full capacity. If you have a 2000 watt inverter, the maximum load should be 1800 watts. As explained earlier, inverter inefficiency means the system consumes more watts than the load.
  • Calculate how much battery power you need. This way you can avoid having to empty the battery as the load is too much. keep that in mind if you want to run something like an air fryer for instance.
  • The battery and inverter cables have to be the right specs. Short, thick wires are ideal, and the shorter the distance between them the better.
  • Use the batteries only as directed. If the manufacturer says recharge at this rate, do it.
  • The inverter battery must have a charge controller.
  • If you are recharging the battery with a solar array, ensure the panels have sufficient power.
  • Always account for inverter efficiency and battery limitations when calculating load runtime.
  • Read the battery and inverter warranty so you have a full understanding in case a replacement is needed.


Buying a 150ah battery is easy enough, but you have to make sure that it is the right one for your inverter. By knowing its capacity, you can rest easy because the system is running at optimum levels.