Buying the right size of a generator has many advantages. Low wattage can cause damage to your appliances. Besides, inconsistent power output, common when a system is overworked, can also cause electrical damage to your devices and even the generator itself. If you also want to avoid hazardous situations caused by poor electricity, you had better have idle capacity over low capacity.

No one size fits all situations when it comes to generators. Even when you have comparable homes, generators might differ from one home to the next. The load size and the job at hand will be different.

The determinants of generator size

• Load size
Load size is the cumulative power requirement for your home and its appliances. Two houses may have the same square footage, but carry different appliances. Furthermore, they may have similar devices, but the appliances may be of different sizes. A bigger fridge means it will need more energy to run.

The total load size is simply a summation of all the watts that each appliance can use. The label is an excellent guide, but it is always good to assume that the appliance will not achieve 100% efficiency and will likely consume more. If you have an old air conditioning unit, you will not consume the same energy as a similar new one. To be safe, you can work with the cumulative total as the benchmark and not the accurate load size.

Sometimes you lose the manual, or you simply didn’t have it because the previous owner lost it, and the device is not properly calibrated. You can use the commonly used power chart. If you cannot find the wattage, but you can see the amperes and voltage, multiply the two to get the wattage of the device.

Notice that the starting and running wattages are different. If a device or appliance has both provided, you may have to add the bigger one to determine the wattage.

• The time required or usage level
If you only need a backup generator for a few hours, you will not need an elaborate system. You may also not need a bigger-capacity generator for such a task because you probably will not need to power appliances in the laundry, family room, or bathrooms.

The situation changes if you expect the generator to run for several days under blackout. In such a case, you will need a larger generator that packs even more features so that you can utilize it at around 75% of its output level so that all its functions can withstand the demanding workload.

• Seasons
If you live in an area that receives violent winters, your backup generator choice must be able to handle robust heating systems or integrated HVAC systems. The same case will apply to someone who experiences scorching summers.

Your running requirements will be at least 20% higher than the load size in normal circumstances. In the case of the two variables, such as seasons and extended usage, 30% is the safer bet. Assume you have a load capacity of 5000. To power a home that has such load, you will need to set the generator at its maximum speed and hope that it is 100% efficient. If it is not, some systems will start failing, and you will be exposed. Again, setting a mechanical device to operate at its end means that it is struggling to retain high levels. Often, mechanical devices should be used at 80-90% to enhance fuel efficiency and longevity.

Conversion of Resistive vs. Reactive loads
Kilowatt-hour is the potential wattage requirement for any electrical appliance. The kilo-volt-amperes kVA is the actual output generated by the generated because they are rarely efficient. The general criteria for choosing a generator is to ensure that the kilowatt-hour requirement matches the actual output.

The table below converts kW to kVA by multiplying kW by the standard factory efficiency level of 80%.

Custom generators
As you may have noticed, similar appliances and homes will not determine the load size. People are increasingly opting for custom-made generators, especially if they have unique requirements. Able Sales diesel generators for sale for a home setting generally start from 5kVA to 20kVA. If you still cannot find a fit within this range, a custom generator that will cater to your needs is an option. This approach is common in the current market for factory-direct sellers.

Custom generators have an advantage because they can come with added features and capabilities. For example, people who want to run heavy consumers of energy can benefit from load-shedding ability. Load shedding is the process of shutting some systems to create room for starting an appliance that consumes high amounts of energy to start. For example, a generator can shed the AC temporarily to power the garage opener. Once the opener is running, it can kick the AC back into the system.

Sizing guide based on the appliances and expected load size

Rated watts: 5
kVA: 4

Description: This offers a basic system for 2-3 survival appliances. Typically suitable for a small single-person unit.

What you can power: A maximum of 4 lights, a fridge, and a fan. It may power the third item, but only when used interchangeably. It can also power a small fan, a small fridge, a sump pump, and essential lighting if all of them are energy-efficient systems.

Rated watts: 6.5
kVA: 5.2

Description: It offers a survival package for a typical family home. Perfect for a family unit that does not pack too many functionalities.

What you can power: All of the above plus a sound system and a television.

Rated watts: 8
kVA: 6.4

Description: Sufficient to power a family home and its critical appliances. Sufficient for a full family unit.

What you can power: All of the above plus oven and dishwasher

Rated watts: 10
kVA: 8

Description: This offers backup power enough to bring complete family comfort. Perfect for an additional unit in a family home, such as a home office, outdoor pool, or functional garage.

What you can power: All of the above plus heating, washing machine, iron, vacuum cleaner, and full kitchen

Rated watts: 15
kVA: 12

Description: The generator powers a family unit sufficiently throughout long movements of power loss.

What you can power: All of the above plus laundry room and a few more appliances for a modern family unit.

Rated watts: 20
kVA: 16

Description: Perfect for a large family unit. It offers security and comfort for full functionality.

What you can power: All of the above plus electric garage, larger air conditioning, and heating systems, and home office workshop.

Rated watts: 25
kVA: 20

Description: Can support a 3000 square-foot house or office with full functionality in the family room, kitchen, laundry room, and bathroom.

What you can power: It can support all of the above plus integrated smart functionalities and HVAC systems.

Sizing importance and approach



Sizing the generator to find the best fit will have many advantages. If you have bought a generator that has a lower output than your load capacity, you will have to make several choices. You will choose to disconnect some of the devices and appliances to ensure that you are not overworking your generator.

You may also use appliances interchangeably to help ease the burden on the generator. If you have not sized it correctly, you will be tempted to think that you have a generator that should offer you uninterrupted services. Instead, you will end up with:

• Automatic shutdowns due to overload
• Decreased product lifespan
• An unsafe environment due to risks of mechanical failures
• High maintenance and repair costs
• Unreliable service delivery
• General system failures
• Potential damages to your assets
• Lost warrant

Misuse of a product is the surest way of voiding your product warranty. If the manufacturer realizes that the recommended usage is 5kVA and you’ve been running a 5.5kVA load with the product, they will most certainly void the warranty if it breaks down.

A beat-up generator will not last long enough to be a return on investment. So, ensure that you are running a comfortable generator. For example, when a 7KVA generator is used to power a 6.2kVA load size, it will not struggle.

The risk of breakdown and mechanical failure is prevalent whenever generators are misused. You also run the risk of causing a fire in your area. The cost of regular breakdowns will be huge for you. Imagine when your backup plan backfires!

• You can instead avoid all this by following the guide above on size or use the AC approach below.

If you are on a tight budget, be aware that low capacity means reduced enjoyment. There is no freedom for you to do as you wish with the electricity. Again, even if money is not a problem, buying an excessively big generator will lead to idle capacity and inefficiencies in terms of fuel. You have to strike a balance for both approaches.

Air conditioner approach
The size of your home determines the size of your AC. So, it is possible to use the AC you are using to calculate the wattage requirement if you do not want to add up each light or appliance in the house. However, you must leave some allowance. Are you heavy on other integrated appliances? If you do, you may want to add a few more kVA on your final buy. Do you have many old systems? If you do, most old electrical systems are highly inefficient and are not energy-smart; they will consume more energy. Again, you will need to add a kVA to cater to this.

Here is the AC approach:

Air conditioner size: 3-ton ac
Generator size required: 14kW or 11.2 kVA
Many old and integrated appliances: +2 kVA

Air conditioner size 4-ton
Generator size required: 17kW or 13.6kVA
Many old and integrated appliances: +2 kVA

Air conditioner size 5-ton
Generator size required: 20kW or 16kVA
Many old and integrated appliances: +2 kVA

Is power loss history a good indicator of the generator to buy?
The correct answer to this question is no. We see online guides recommending that if you lose power often, you need a large inverter standby generator. They will also suggest that if you rarely lose power, a medium-sized and portable inverter will be sufficient.

This cannot be further from the truth. If power is lost and your big mansion only has a bath tab, can you power the bath tap with a medium-sized inverter while still running the AC unit and lighting? You will probably not be able to do that. So, you will struggle to power basic survival appliances inside your house. If it is winter and your heating system wants a share of the pie, your generator will be a huge disappointment.

You probably get an average of 6 year's blackout the whole year, but you will be surprised to know how long that can be in winter or summer. Thirty minutes in the cold or without any other survival appliance can easily expose your health. So, you want a generator that powers exactly what you want. It does not matter whether it will be used for 5 minutes in a whole year or not.

Portable vs. Standby Generator
Both types of generators will be excellent for any home as long as there is a professionally installed transfer switch. The portable generator can be used outdoors, at job sites, and other functions whenever it is not in use at home. However, it will not offer you a timely backup because it is not automated. Standby generators are automated so that your home runs uninterrupted. Imagine you have a pet, and electricity is lost while you are away. If there is no standby generator to power your AC, you might find your pet freezing by the time you come back. If you had something in the fridge, it might go bad in the process.

When you want a generator to serve you for a long time faithfully, ensure that you are giving it a load its size. It makes sense for everyone when a heavyweight takes on a fellow heavyweight, and the same case applies to a generator. Calculate the load size faithfully without ignoring the starting load size. Also, ensure that you have given attention to all the appliances in the house, including outside the pool, garage opener, gaming console, and any other device. Sometimes you may not have the patience or time to do all these maths; you can use comparable homes, AC size, or even bring in an electrician to do the evaluation.