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In solar panel systems, the inverter usually draws power from a battery bank to run appliances. So if you have a 3000 watt inverter, how many batteries or what size will you need? The answer is not as difficult as it seems to figure out as we will show.
It takes a 24V 150ah battery to run a 3000 watt inverter. This battery has a capacity of 3600 watts, so the inverter can run for a little bit over an an hour.
How to Calculate 3000 Watt Inverter Battery Requirements
If you have any experience using solar panels, you will be familiar with the calculation formula. But if not the process is straightforward.
Multiply the watts by the battery voltage and you get the amp hours required to run the inverter with a full load. If you are going to buy a 12V battery for instance:
3000 / 12 = 250
A 3000 watt inverter will need a 12V 250ah battery to run at full power, that is with a full load. The runtime will be 1 hour more or less, depending on the inverter efficiency and battery discharge rate.
If you opt for a 24V battery instead the battery bank size is reduced:
3000 / 24 = 125
The same inverter will run at full power for an hour so on a 125ah 24V battery. Many inverters support 24V batteries , and while these batteries cost more you can get by with a smaller capacity.
A 150ah 24V battery is the minimum required to power the inverter. With the Lossigy 24V LiFePO4 100AH you can keep the inverter going for 60 to 70 minutes. If you want a longer running time, double the battery capacity.
A battery bank is mandatory for an off the grid system. But some grid tied homes prefer to have a battery bank just in case the power goes out Solar power in grid tied systems are shut down automatically during a power outage for safety reasons, but with a battery bank you run basic appliances.
How Long Will Batteries Last on a 3000 Watt Inverter?
In the examples above the assumption is the inverter runs with a full load for one hour. For other scenarios you can use the following calculations, and they are applicable for any battery voltage.
Inverter power load watts x runtime = required amp hours
Suppose you want to run a 1800 watt load for 3 hours. You can calculate it as follows:
1800 x 3 = 5400
That is 5400 watts. To convert into amps, choose the appropriate battery voltage.
5400 / 12V = 450
540 / 24V = 225
To run a 1800 watt load for 3 hours, the inverter requires either a 12V 450ah or 24V 225ah battery.
If you can get a 12V 450ah battery bank that is good, if not you can get any combination as long as the total is at least 450ah. A couple of 250ah batteries will do for instance. The same rule applies for 24V batteries.
But as pointed out previously, these are the minimum sizes. Running the inverter with these loads will result in a full discharge. That is not recommended for deep cycle batteries, as they have to be recharged at the 50% level.
If you need to run those loads mentioned above, you have to double the capacity. So instead of 450ah 12V for a 1800W load, make it 900ah. And you should get a higher battery capacity because a low inverter efficiency rating will mean a higher power consumption.
How Inverter Efficiency Affects Battery Consumption
There is one more factor that needs to be considered here, the inverter efficiency rating and its effect. The best results come from inverters with high efficiency ratings. The lower the inverter efficiency rating, the more battery power is used.
The inverter efficiency rating determines how much energy is conserved during the conversion process. Inverters, as you may know, converts DC into AC power. This procedure leads to some energy loss and its efficiency is key.
The lowest acceptable inverter efficiency rating is 85%, with newer ones at 90% to 95%. As we will explain, the rating is the reason why calculations for inverter runtimes are estimates at best.
How to Calculate Inverter Efficiency
In a perfect world, a 3000 watt inverter will generate 3000 watts an hour. But that is not the case. Assuming the inverter is 95% efficient, it means 2850 watts have been converted from DC to AC.
3000 x .95 = 2850
This also means a 3000 watt load will consume about 3157 watts.
3000 + 5% = 3157
If the inverter efficiency rating is 85%, only 2550 watts are available for your load.
3000 x .85 = 2550
And this also means a true 3000 watt load would require almost 3500 watts. This is why you often see solar power experts recommend doubling the inverter size for whatever load you want to run.
You can double the inverter size, but it is not always necessary. If you rarely run the system with a full load, the inefficiency rating will not matter much.
Suppose you regularly load 1800 to 2000 watts on the system. A 3000 watt inverter can run the load whether it is an 85% or 95% rated system. This only becomes an issue when the load is close to 3000 watts.
Is a 3000 Watt Inverter Enough?
A 3000 watt inverter can run a lot of appliances , but is it enough for you? The answer depends on how much power you consume and the batter bank size.
Assuming the inverter has at least a 500ah battery bank, it should be able to run a TV, movie player, lights and a fan at the same time for hours. You can run a laptop, printer, speakers and lights without a problem.
3000 watts is enough to run some power tools, kitchen appliances and some motors as well. A room air conditioner needs 1500 running watts and 2000 surge watts, so it is not a problem either.
An energy efficient fridge needs about the same amount of surge watts as a room AC, same with a clothes washer, dishwasher, hair dryer and a furnace fan.
In other words you can run most appliances on this inverter size, but the only question is for how long. The answer of course depends on the inverter power source.
If your system is on the grid, the inverter can draw from electrical power and run for as long as there is power. If you are using a battery bank, the inverter runtime depends entirely on the available power.
To answer the question if this inverter size is enough, it depends. If you have another power source, a small home or don’t use a lot of appliances, it might be. But for a typical household, 3000 watts is too small. The easiest way to find out is to check your monthly bill.
Even if your power usage is under 3000 watts, you have to find a way to recharge the batteries, if that is your power source. A good option would be solar panels, which can recharge the battery during the day. A 3000 watt solar array can recharge a 500ah battery bank with enough sunlight.
lastly you need to make sure the inverter is of high quality. We recommend the GoWISE Power PS1004, a pure sine wave inverter with 3000 continuous running and 6000 watts peak capacity.
5 Tips For Running a 3000 Watt Inverter
- Check your monthly power consumption. This information will be in your monthly bill. List all the appliances, tools and devices you want to run on the inverter and for how long.
- Plan ahead. Once you have done the steps above, it is easy to determine if a 3000 watt system is enough.
- Choose a battery type. Most inverters support 12V and 24V batteries, but many of the newer systems now only run 24V. You can connect multiple 12V batteries in a series to get 24V, but they will take up a lot of space, so decide which voltage system to go with.
- Check the inverter efficiency rating. Do not buy anything less than an 85% rated inverter, the higher the better.
- Do not run the inverter to the limit. As we have shown in the calculations above, a 3000 watt inverter will use more than 3000 watts per hour due to inefficiency. So if you need to run a full load, get a higher capacity system.
With the cost of 3000 watt inverters going down, it comes as no surprise that it is becoming the preferred choice of many solar powered homes. By knowing how many batteries are required, you can configure the system to run efficiently.