How to Choose the Right Inverter and Battery Size
Whenever someone asks us why their newly bought inverter stops working during a power cut the answer is usually the same. They guessed their home load instead of calculating it. When you are planning for an Off Grid solar setup or even a normal home inverter doing the math properly is extremely important.
Why is Inverter Size Calculated in VA and Not Watts
You probably noticed that we calculate your appliances in Watts but the inverter output is shown in VA which stands for Volt Ampere. This happens because of something called Power Factor. Most appliances waste a tiny bit of electricity while running.
A typical home inverter has a power factor of 0.8. So if your total running load is 800 Watts you cannot buy an 800 VA inverter. You need to divide 800 by 0.8 which gives you 1000 VA. Our calculator automatically adds this 25 percent safety margin so your inverter never overloads and trips when you switch on a heavy appliance.
Tubular vs Lithium ion Which Battery is Better
When you use our calculator above you will notice that changing the battery technology changes the required Ah capacity. Traditional lead acid tall tubular batteries have a Depth of Discharge DOD of around 70 percent. This means you can only use 70 percent of the stored power before the battery needs to be recharged safely.
On the other hand Modern Lithium ion batteries have a DOD of 90 percent to 95 percent. They are highly efficient charge much faster and last almost 10 to 15 years. Although Lithium ion costs more initially it requires a smaller Ah size for the same backup time and provides a much better return on investment over the years.
Expert Pro Tip
Never connect heavy loads like air conditioners geysers or water pumps to a standard 12V or 24V inverter battery setup. If you face frequent power cuts and want to run heavy appliances you will need a high capacity 48V Off Grid solar system with heavy duty Lithium ion batteries.