Last Updated on July 25, 2022 by Jahangir

In the event of a power outage, a generator is vital to provide power for a home or a business. In times when your home’s main electrical service is unavailable or not working properly, a standby generator provides continuous, reliable backup electricity. Additionally, it protects your electric system from under voltages and other problems. However, what size generator do I need for my house? You can choose the right type of generator for your needs with the following information:

## What size generator do I need to run my whole house?

In order to purchase a generator, we have to decide what kind we need. Diesel engines are more efficient, so we can choose them. A regular gasoline engine generator would suffice if you want to power a small appliance like a TV, light, or fan. The next step is to determine the power requirements of each individual piece of electrical equipment. Adding amps and volts is simply a matter of multiplying them together or checking the equipment specifications to get the wattage. In order to determine the required size of the generator, I divided the significant tasks into some steps. Here are the details-

### Step 1 – Make the list of devices you want to run

It is imperative that we first determine how many lights are in our home. Secondly, we need to find out the number of electric fans in our house. Next, we should figure out how many electric water heaters we have in our home. In addition, we should find out how many televisions or other electrical devices we have in our home. In this case, I considered 10 LED lights, 5 Fans, 3 AC, 1 Refrigerator, 1 water pump and 1 TV to be the significant devices that needed to be powered.

### Step-2: calculate the total power requirements for your selected appliances.

Calculate the total wattage of your required equipment once you have completed the list of equipment. Hence, the total wattage can be calculated according to the following: –

It is important to note two things: the starting current may be higher than the running current of some electrical devices like water pumps, air conditioners, refrigerators, and so on. The manufacturer of the equipment will provide you with information regarding the equipment. There is no need to worry in this regard. Because the wattage of an electrical device can differ between manufacturers, this rating is always checked.

Power in watt: Sometimes, you can find the unit of the equipment other than watt as shown in the below picture.

In this case, you need to convert this unit to watt. If we consider the above technical specification, here the power of the pump/motor is 0.75Hp. We know 1Hp is equal to the 0.746 Kilowatts. Then 0.75Hp=0.55KW. This is also mentioned in the above specification. But, some manufacturers do not display in KW. They only show the unit in HP. However, now convert the KW to W and we know 1000Watts is equal to 1KW. So the watt of this water pump is 0.55KW=0.55*1000=550watts

**Step 3- Consider safety factor**

Once you find the total watt of your electrical devices, you should consider the safety factor as 20%. This will help you to protect your generator from overload and in case if you want to increase the load in future, then you can do it. So, the safety factor is very important to consider during buying your first generator. From the above calculation, we have found the total load of the house is 6400Watts. Now consider the safety factor as 20%, then the total load

6400+6400*0.2=6400+1280=7680watts

**Step 4 – Convert watt to VA to calculate the size of the generator**

Now, we can calculate the size of the generator. The formula is simple. In most cases, the generator manufacturers use the generator capacity as VA i.e. Volt*Ampere. This is very simple to convert the watt to VA. In this case, we will apply the most common as well as very important formula as P=V*I*Cosθ [I have considered single phase because most of our house/home is used single-phase current].

Here, V*I is the VA and Cosθ is the power factor. The average power factor is 0.80. So I am assuming the power fact is 0.8 in this case.

So, we get, 7680=VA*0.8

VA=7680/0.8=9600VA

So, you should select a 10,000VA generator for the above load. You can easily calculate the size of your required generator by using the above calculation. If you still face any issues, please contact us. We will help you to sort out your required generator.

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Mr. Jahangir Alam is an Electrical & Electronics Engineer with a wide range of experience in several fields of Engineering. He finds engineering articles to be very interesting, and that is why he likes to write them. To know more about him, please click here.