How many 100w solar panels are needed to power a house?

The amount of power required from a solar panel varies from house to house. These power devices have batteries and panels of different sizes, which determine the amount of power they can absorb and store. Principally, the big the size of the panel and the capacity of the battery, the higher the amount of power.

The power consumption depends on the total number of electric devices and their running time. For instance, if you have a refrigerator running most of the time, your power consumption might be higher than a household with only a television powered at night only. This article will discuss more about a 100w solar panel to help you decide if it is right for you.

How to calculate power requirement 

The first thing to help you determine the power needed from the solar panel is calculating your daily or monthly consumption. You can get your power consumption by checking your previous electricity bills or checking the reports from the whole house monitoring system. These monitors are connected to the main breaker panels. 

Even better, some of them have wireless support such that they can send the data directly to your phone or pc. However, if you are dealing with a lower budget, you can look for a monitor system with an LCD to display the power consumption reports.

On the other hand, if this is the first time you are installing a power source in your house, you might not have any prior data to make inferences from. Moreover, it might be expensive to install a power monitor system. Solution? When in such tight situations, you can opt to calculate the power consumption all by yourself manually. Don’t freak out! We will give you an example to guide you through!

Follow the below steps to calculate your power consumption.

Step 1: Estimate the total time per day the appliances run

The first thing is to record the total time you run all the electric appliances per day. If you are a perfectionist, it would be best to keep a record of the usage for the whole week. For instance, you can note down the total amount of time you used a microwave, computer, or fan for the whole week. Then, you should find the average of their sum. This is what I mean


You used a refrigerator for 3 hours, 2 hours, 0.5 hours, 1 hour, and 4 hours for  five days consecutively

Fan for 4 hours for five days

Watched television for 1 hour, 2hours, 0.5hours, 2.5 hours, 4 hours for five days;

To get the average time;

Find the total sum of the hours; 


3+2+0.5+6+4= 15.5

Average time= 15.5/5= 3.1


4 X 5=20

Average time

20/5= 4


1+2+0.5+2.5+4 = 10

Average time per day

10/5= 2

Nonetheless, it will not harm much if you choose to make a rough estimate. For instance, if you switch on the television only when you are back for approximately four hours in the evening, you can assume it to be the standard figure for all other days. 

Step 2: Calculate the wattage of the product

Next, you need to calculate the wattage of the devices

In most cases, the appliances have a wattage stamp on the back or on their nameplate. However, the easiest option would be to look at the manual if you still have it. 

Also, you should note in some cases, manufacturers may stamp only the voltage consumed and the current in amperes. Consequently, you must calculate the power using this formula;

Power (in watts) = voltage (v) X current (amps)

For example, if the electric kettle consumes 120 volts at a current of 1.5 amperes;

Power= 120 X 1.5= 180 volts.

After identifying or calculating the wattage, next, you should calculate the energy consumed and convert it to kilowatts;

Power consumed= wattage X hours used per day

For instance; assume 

The refrigerator has a power rating of 200w, running for 3.1 hours

200w X 3.1H= 620 W

A 50w ceiling fan running for 4 hours per day

50W X 4= 200W

A 70W LCD TV running for 2 hours per day

70W X 2= 140W

Three 20W fluorescent lights running for 8 hours

3X 20W X 8= 480W

The total amount of power consumed= 620W + 200W + 140W + 480W= 1440 watts

We convert it to kilowatts 1440/1000= 1.440Kw.

Step 3: How much energy can a solar panel generate over some time?

The power generated by the solar panel is rated in watts. In our case, we have a 100w solar panel. To calculate the total power generated by the panel, multiply the power rating of the solar panel with hours exposed to the sunshine. Then multiply with 0.85, which is considered as the efficiency factor for solar panels.


100w X 4 hours X 0.85= 340 Watts.

Thus, you will require 1440/340= 4.2 panels ~= 5 panels. 

Nonetheless, you should note that the power produced by a solar system fluctuates depending on several factors. For instance, some areas experience short periods of sunshine which might mean a lower amount of energy per day. Also, you should ensure that you position the device strategically to absorb the sunlight efficiently.

Principally, the solar system should match the needed energy, or even better, exceed it. Thus in our case, you will need more than one panel to meet the required power.

How much does a 100-watt solar panel cost?

The pricing of solar panels varies according to their efficiency and the brand. Generally speaking, a typical 100w solar pane may cost approximately $100 to over $ 300.  Hence, if you need four units, it may cost you approximately $ 400 to $1200.


Can you connect multiple 100-watt panels?

Yes, you can connect multiple solar panels to increase their total output. Basically, you should ensure that the output matches or exceeds the power consumption. 

Can you power a home with a 100-watt solar panel?

A: yes, you can. However, most people don’t prefer using a 100-watt panel because a single unit will not be sufficient. Thus, you will need more than two units that might be inconveniencing financially, and also, the storage space might be an issue.

What is the size of a 100-watt solar panel?

A:  a typical 100-watt panel measures round 47 X 21.3 X 4 inches.  Thus the total required area is approximately 1001.1 square inches

Final words

Solar panels have a specific amount of power they can generate in a given amount of time.  Similarly, houses have different power consumption rates that depend on the total number of appliances and their running time. Consequently, it would help if you calculated the total power needed to get a reliable solar panel. Fortunately, you can connect several solar panels to increase their output which will help meet the house requirements.

We have discussed a step-by-step process of calculating the household power consumption and the total number of units required. In case your device does not have a power rating, you can multiply the voltage with the current to get the power. Lastly, don’t forget that the solar system should exceed or match the total power consumption if you are not ready to stay in darkness.


I’m Matt, a computer and electronic embedded system developer. Currently, working as an electronic engineer. In my leisure time, I do love to blog about technology stuff. Specially, new advance high tech devices. Portable solar systems are one of topic that I love to investigate. They are becoming more powerful day by day which keep me alert.

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