## Why do we calculate daily energy consumption?

Daily energy consumption is an important figure when DIY an off-grid solar energy system.

It directly determines the **battery capacity** and the **number of solar panels**, as well as the **cost of the entire off-grid power system**.

### Calculation of battery pack capacity

For example:

Your average daily energy consumption is 3 kWh and you need to design a 24V off-grid system and want it to be able to independently support 2 days of household energy consumption in case of power outages.

Then battery capacity = (3kWh x 2)/24V = 250Ah

That is, you can use 8 LiFePO4 battery cells of 3.2V 230Ah and BMS to form a 24V 230Ah battery pack.

Or you can use 8 3.2V 280Ah LiFePO4 battery cells to form a 24V 280Ah battery pack.

### Calculation of the number of solar panels

Let’s take a 24V 280Ah battery pack as an example to see how many solar panels you need.

Suppose you live in the California area and the average peak sun hour is 5 hours per day.

Energy of the battery pack = 24V x 280Ah = 6.72kWh

Total energy of solar panel = 6.72kWh / 5 = 1.34kWh

If you plan to use solar panels with a power rating of 200W, then the number needed is

1.34kWh / 0.2kWh = 6.7

So you need at least 7 solar panels.

* If you don’t know the Peak Sun Hour for your location please see here.

### System Cost

Once you confirm the capacity of the battery system and the number of solar panels, You can roughly estimate their costs.

The price of 8 x 3.2V 280Ah LiFePO4 batteries with shipping is $1462 (slow shipping) ~ $1842 (fast shipping).

An 8S 24V 100Ah BMS is $80.

200W 24V solar panel is about $200, the price of 7 pieces is 7 x $200 = $1400.

So in this off-grid solar energy system, the price of the battery and solar panel will be $1462 + $80 + $1400 = $2942(slow shipping)

Or $1942 + $80 + $1400 = $3422(fast shipping)

## How to calculate daily energy consumption

Daily energy consumption is usually measured in “kWh”. And the power of household appliance is usually rated in “W”.

The energy consumption formula is

**Energy consumption (kWh) = rated power (W) x usage time (h)/1000**

For example:

There are 5 daily used appliances, their power consumption and usage time are as follows.

- Appliance 1, 300W, 2 hours
- Appliance 2, 20W, 4 hours
- Appliance 3, 1000W, 15 minutes
- Appliance 4, 10W, 1 hour
- Appliance 5, 100W, 30 minutes

Then daily energy consumption is

300W x 2h/1000 + 20W x 4h/1000 + 1000W x 0.25/1000 + 10W x 1h/1000 + 100W x 0.5h/1000 = 0.99kWh

Alternatively, you can use our prepared daily energy consumption calculator.

## Energie Panda Daily Energy Consumption Calculator

There are many Lithium Iron Phosphate battery suppliers, but **Energie Panda** provides you brand new grade A LiFePO4 battery cells.

Any question and inquiries please send email to info@energiepanda.com, we answer quickly.

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