Load Analysis

First we have to start by putting our loads in the table. Name your device and include the power (watts) of the device together with the hours of intended use. Enter one hour of use as '1'. If you are using a device for 15 minutes, then use the formula: 60min/15min=0.25

If you are submitting the power rating, make sure you know if it's AC or DC. If you don't see the power rating on an appliance, multiply current (amps) by voltage (volts).

DC Appliances

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W
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AC Appliances

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Minimum Inverter Requirements

In this section, you are going to select your system voltage. It is better to select a higher voltage battery because the thickness of your cables depends on it.

Look at your AC appliances. If you have a blender of 1000 watts, then I recommend getting an inverter of 1250 watts (1000W*1,25) . 1,25 is a safety factor so the inverter doesn't run at 100% all the time. If you have multiple AC appliances running at the same time, you have to add them together.

I recommend a few limits for the inverters below.

  • 12V battery system -> inverter below 1000W
  • 24V battery system -> inverter from 1000-2000W
  • 48V battery system -> inverter from 2000W to 4000W
  • More inverter power -> have multiple inverters in parallel

Days of Autonomy

This is as a backup if the sun doesn't shine. I recommend having at least three days worth of energy stored in your batteries. We will size the battery bank according to these amount of days. Later, we will calculate how much solar is needed to charge these batteries in one sunny day.

Days

Battery Size

Here you can see the calculated battery sizes according to the values you entered. You will see that you need more capacity if you choose for lead-acid. This is because you can only use 50% of a lead-acid battery without damaging it. Further, the efficiency of a lead-acid battery is 80%. For lithium we can use 80% of it's capacity and it has an efficiency of 99%.

Ah
Ah
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Wh

Required Solar Panels to Charge the Battery

In this section, we calculate the total power of solar panels you need to charge the battery in one sunny day. The number of sun hours per day can be seen on this website. For the USA, this can be from 3-6 hours. It depends on the season and latitude. Choose the lowest number if you want to use your battery all year-round.

Hours/day
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Watts

Send Report to Email

You can send this report to your email by filling in your email address and clicking the 'send pdf to email' button. You will receive the PDF in your inbox. Make sure to check your spam folder too.