When the power goes out, owning a generator is only part of the solution. You also need a safe and practical way to get generator power into your home's electrical system.
For homeowners using a portable generator for backup power, two common options are a generator interlock kit and a manual transfer switch.
Both can allow a generator to supply household circuits when properly installed, but they work differently. They also provide different levels of flexibility and require different approaches to managing the generator's available power.
If you're researching generator interlock kit vs transfer switch, this guide explains the differences, advantages, load-management considerations, generator sizing, and questions to consider before choosing a home backup-power system.
Why You Need a Safe Generator Connection
During an outage, a properly sized generator can help keep important equipment operating, including:
- Refrigerators and freezers
- Furnaces
- Selected air-conditioning equipment
- Well pumps
- Sump pumps
- Lights
- Internet equipment
- Medical equipment
- Selected kitchen appliances
- Other essential household circuits
Hardwired equipment normally receives electricity through your home's electrical panel. Supplying these loads from a portable generator therefore requires an appropriately designed connection between the generator and the electrical system.
Attempting to energize a home's electrical panel by connecting a generator through an ordinary appliance receptacle can create a dangerous backfeeding condition.
A properly designed transfer or interlock arrangement prevents generator power and utility power from supplying the home's electrical system at the same time.
This is important for protecting the home's electrical equipment, the generator itself, and utility personnel who may be working on power lines during an outage.
Generator connections should always comply with manufacturer requirements, local electrical codes, and applicable regulations. Installation should be performed by a qualified electrician.
What Is a Generator Transfer Switch?
A generator transfer switch provides a controlled method of changing the electrical source supplying designated household circuits.
During normal operation, those circuits receive utility power.
When utility power fails, the homeowner can start the portable generator and manually transfer the designated circuits from utility power to generator power.
A manual transfer switch commonly contains breakers for specific circuits selected for backup power.
For example, a homeowner might configure backup power for:
- Refrigerator
- Freezer
- Furnace
- Sump pump
- Well pump
- Kitchen outlets
- Internet equipment
- Several lighting circuits
Instead of attempting to power everything in the house, the transfer switch concentrates the generator's available capacity on the circuits considered most important.
Advantages of a Manual Transfer Switch
One of the biggest benefits of a manual transfer switch is predictable load management.
The backup circuits are determined during installation. A qualified electrician can evaluate generator output and distribute the selected electrical loads appropriately.
That can make operation relatively straightforward during an outage.
Once the generator is connected and operating correctly, switching to generator power supplies the circuits included in the transfer-switch configuration.
This approach can be particularly attractive for households where several family members may need to operate the backup-power system.
Potential Disadvantages of a Manual Transfer Switch
A traditional manual transfer switch generally powers only the circuits connected through that switch.
If an outlet or appliance wasn't included when the system was installed, it usually won't become available simply because the generator has unused capacity.
That restriction reduces flexibility, although it can simultaneously make generator load management easier.
What Is a Generator Interlock Kit?
A generator interlock kit takes a different approach.
Instead of installing a separate panel containing selected backup circuits, an approved interlock mechanism works with breakers in the home's main electrical panel.
The mechanical interlock is designed so the main utility breaker and generator breaker cannot both be switched on simultaneously.
In simplified terms:
Normal utility operation:
Utility → Main Breaker → Electrical Panel → Home Circuits
Generator operation:
Generator → Generator Inlet → Generator Breaker → Electrical Panel → Selected Home Circuits
When generator power is being used, the main utility breaker remains off.
The interlock physically prevents the generator breaker and main breaker from being placed in their operating positions simultaneously.
Why Do Homeowners Consider Generator Interlock Kits?
The primary attraction is flexibility.
Because generator power reaches the main electrical panel, homeowners may be able to choose which household circuits they want to operate rather than being restricted to circuits installed in a separate transfer-switch panel.
For example, you could potentially power your refrigerator and furnace during one part of an outage, then temporarily switch off another circuit before operating a different appliance.
However, that flexibility comes with an important responsibility:
The homeowner must actively manage electrical loads.
Generator Interlock vs Transfer Switch: Key Differences
| Feature | Generator Interlock Kit | Manual Transfer Switch |
|---|---|---|
| Uses main electrical panel | Yes | Usually uses designated backup circuits |
| Access to household circuits | Potentially broad | Limited to configured circuits |
| Load management | Primarily homeowner managed | More controlled by system configuration |
| Flexibility | High | Moderate |
| Ease of operation | Requires understanding of loads | Generally straightforward |
| Overload management | Requires careful attention | Easier to control through selected circuits |
| Professional installation | Recommended/required as applicable | Recommended/required as applicable |
One important point is often overlooked:
Neither system increases your generator's actual electrical output.
A 7,500-watt generator remains a 7,500-watt generator regardless of whether it connects through an interlock or transfer switch.
The connection method determines how that available power is distributed and controlled.
The Biggest Difference: Generator Load Management
Understanding generator capacity is one of the most important parts of designing a home backup-power system.
Generators have limits.
If your generator can supply 7,500 running watts, the combined electrical demand placed on it needs to remain within the generator's operating capacity.
A home, however, can easily contain appliances whose combined demand substantially exceeds that amount.
Consider equipment such as:
- Central air conditioners
- Electric water heaters
- Electric ranges
- Clothes dryers
- Well pumps
- Furnaces
- Refrigerators
- Freezers
Several of these loads operating simultaneously can overwhelm a portable generator.
Load Management With a Transfer Switch
A manual transfer switch can simplify this problem because only selected circuits are connected to the backup system.
During installation, the electrician can help determine which circuits should receive generator power based on the generator's available capacity and the homeowner's priorities.
This naturally restricts the number of loads that can operate from generator power.
Load Management With an Interlock Kit
An interlock may make generator power available through the main electrical panel, but that doesn't mean every breaker should remain on.
Homeowners need to understand:
- Generator running watts
- Generator surge or starting capacity
- Appliance starting watts
- Appliance running watts
- 120V versus 240V loads
- Which circuits are essential
- Which large loads should remain off
For example, simultaneously attempting to operate central air conditioning, an electric water heater, well pump, electric range, and numerous household loads may exceed the capabilities of many portable generators.
Having access to a circuit does not necessarily mean the generator has enough capacity to power it.
Generator Starting Watts vs Running Watts
This becomes particularly important when comparing generators for home backup.
Electrical equipment containing motors or compressors often requires more power when starting than while operating normally.
Common examples include:
- Air conditioners
- Refrigerators
- Freezers
- Well pumps
- Sump pumps
- Furnaces
- Certain power tools
Suppose an appliance requires 1,500 watts while operating but temporarily requires considerably more power when its motor starts.
Your generator needs sufficient capacity for both the continuous electrical load and temporary starting demand.
This is one reason homeowners shouldn't choose a generator based solely on a simple total of appliance running watts.
Can a Generator Run Central Air Conditioning?
Possibly, but this requires careful generator sizing.
Central HVAC systems can represent one of the largest electrical loads in a home or commercial building.
Whether your generator can operate an air conditioner depends on factors including:
- Generator output
- Air-conditioner capacity
- Compressor starting requirements
- Voltage
- Phase
- Other electrical loads operating simultaneously
- HVAC equipment specifications
- Electrical configuration
For larger HVAC applications, read AC Units For Less' Standby Generator Sizing Guide for Commercial HVAC Equipment, which takes a closer look at factors such as MCA, MOCP, compressor starting requirements, and other considerations that affect generator sizing.
Homeowners interested in maintaining air conditioning during an outage should have both the HVAC system and generator requirements evaluated before purchasing backup equipment.
This is particularly important when you're purchasing a generator specifically for whole-home or HVAC backup.
30-Amp vs 50-Amp Generator Connections
Portable home-backup generators commonly use 120/240V connections, with 30-amp and 50-amp configurations being common.
A larger receptacle or inlet doesn't automatically mean a generator can power an entire home.
Generator capacity ultimately depends on the generator's rated electrical output.
Before selecting an inlet, transfer equipment, cord, or generator, verify compatibility between all components.
Your electrician should also confirm:
- Conductor sizing
- Breaker sizing
- Grounding
- Neutral configuration
- Generator output
- Transfer equipment compatibility
- Applicable electrical-code requirements
Generator Grounding and Neutral Configuration
Generator grounding can become more technical than many homeowners expect.
Portable generators may use either a bonded neutral or floating neutral configuration.
Different transfer equipment can also handle the neutral differently.
The correct arrangement depends on the generator, transfer equipment, service configuration, manufacturer's instructions, and applicable electrical codes.
Improper neutral-to-ground bonding can create electrical hazards.
For that reason, don't assume that grounding instructions from one generator installation apply to another.
Have a qualified electrician determine the correct configuration for your specific generator and electrical system.
Interlock Kit vs Transfer Switch: Which Setup Fits Your Needs?
The answer depends largely on how you want your backup-power system to operate.
A Transfer Switch May Suit Homeowners Who Want:
- Clearly defined backup circuits
- Straightforward operation
- Easier load management
- Less decision-making during an outage
- A backup configuration that multiple household members can understand
An Interlock Kit May Suit Homeowners Who Want:
- Greater flexibility in selecting circuits
- Access to more circuits through the main panel
- The ability to change which loads receive power
- Direct involvement in generator load management
An interlock setup requires the operator to understand the generator's limitations and carefully manage which breakers are operating.
The appropriate configuration ultimately depends on the home's electrical system, local requirements, generator capacity, and the loads you want available during an outage.
Portable Generator vs Standby Generator
There's another important question worth asking before investing heavily in a portable-generator connection:
Would a Briggs & Stratton standby generator better match your needs?
Portable generators can be an excellent solution for temporary emergency power, particularly when the goal is keeping essential circuits operational.
A permanently installed standby generator provides a different experience.
Depending on the system, a standby generator can automatically detect a utility outage and provide backup power through an automatic transfer system.
This can be particularly useful for homes and properties with:
- Frequent power outages
- Medical equipment
- Well pumps
- Sump pumps
- Refrigeration requirements
- Home offices
- Larger HVAC loads
- High backup-power requirements
Homeowners and businesses can shop Briggs & Stratton standby generators at AC Units For Less to compare residential and commercial backup-power options across multiple capacities and applications.
How Big of a Generator Do I Need for My House?
One of the most important decisions when planning backup power is choosing the correct generator capacity.
If you're comparing common residential standby-generator sizes, read our 13kW vs 18kW vs 22kW vs 26kW Standby Generator Guide for a more detailed comparison.
One important rule:
Don't choose a generator based on the square footage of your house alone.
Start with what you actually need to operate during an outage.
Create a backup-power checklist containing each essential load:
| Equipment | Running Watts | Starting Watts | Priority |
|---|---|---|---|
| Refrigerator | Check equipment | Check equipment | High |
| Furnace | Check equipment | Check equipment | High |
| Well Pump | Check equipment | Check equipment | High |
| Sump Pump | Check equipment | Check equipment | High |
| Freezer | Check equipment | Check equipment | High |
| Internet | Check equipment | Check equipment | Medium |
| Lights | Check equipment | Check equipment | Medium |
| Air Conditioner | Check equipment | Check equipment | Varies |
Then identify which loads could operate simultaneously.
This provides a much better starting point for determining generator capacity than choosing a generator based solely on home size.
13kW vs 18kW vs 22kW vs 26kW Standby Generators
Residential standby generators are available in several capacities, and bigger isn't automatically better.
The appropriate size depends on the loads you expect the generator to support.
A smaller standby generator may be sufficient when your priority is keeping essential equipment running, such as:
- Refrigerator
- Freezer
- Lights
- Furnace
- Internet
- Selected outlets
A larger generator may be necessary when your backup-power goals include equipment such as:
- Central air conditioning
- Multiple HVAC systems
- Electric water heating
- Well pumps
- Larger kitchen appliances
- Additional household circuits
If you're currently comparing generator capacities, see the AC Units For Less 13kW vs 18kW vs 22kW vs 26kW Standby Generator Guide before choosing a system.
Planning a Complete Home Backup Power System
A generator purchase should be approached as a system, not simply as an engine that produces electricity.
Depending on the installation, your complete backup-power solution may include:
- Generator
- Transfer switch or approved interlock
- Generator inlet
- Properly sized power cord
- Circuit protection
- Appropriate wiring
- Load-management strategy
- Fuel supply
- Safe generator placement
- Professional electrical installation
Planning these components together helps prevent the frustrating situation of purchasing a generator and later discovering that it doesn't match the home's electrical requirements or intended loads.
What About Commercial Standby Generators?
Commercial facilities have substantially different backup-power requirements than most residential properties.
HVAC equipment, refrigeration, pumps, lighting, communications, servers, security systems, and other critical equipment can dramatically increase generator demand.
Commercial generator sizing should account for:
- Total connected load
- Essential versus nonessential loads
- HVAC compressor starting requirements
- Motor starting loads
- Voltage
- Phase
- Transfer-switch requirements
- Load sequencing
- Future electrical demand
If HVAC equipment represents a significant portion of your emergency load, start with our Commercial HVAC Standby Generator Sizing Guide.
AC Units For Less also carries larger Briggs & Stratton commercial generator options, including the 80kW Briggs & Stratton Standby Generator, for applications requiring considerably more backup capacity.
Generator capacity, voltage, phase, starting loads, fuel requirements, and transfer equipment should all be evaluated before selecting a commercial generator.
Why Consider Briggs & Stratton Standby Generators?
Briggs & Stratton is a well-established manufacturer in the power-equipment industry and offers standby generator solutions for residential and commercial applications.
Rather than choosing a generator based only on advertised kilowatts, compare specifications that matter to your actual application.
These can include:
- Rated generator capacity
- Fuel type
- Voltage
- Phase
- Motor and compressor starting requirements
- Transfer-switch compatibility
- Physical installation requirements
- Warranty
- Service requirements
- Intended residential or commercial application
AC Units For Less offers a growing selection of Briggs & Stratton standby generators, making it possible to compare different capacities for home, HVAC, and commercial backup-power applications.
How to Choose a Generator for Your Home
Before purchasing a generator, answer these five questions:
1. What absolutely needs power during an outage?
Make a list of essential equipment rather than assuming the entire house needs backup power.
2. What are the running and starting requirements?
Pay particular attention to equipment containing motors and compressors.
3. Do you need your central HVAC system?
This can significantly change the generator capacity required.
4. Do you want portable or automatic standby power?
A portable generator and a permanently installed standby generator solve the outage problem differently.
5. How will generator power enter the home's electrical system?
Discuss the transfer switch, automatic transfer switch, or approved interlock configuration with a qualified electrician before purchasing equipment.
Once you've answered these questions, compare generator capacities rather than simply shopping for the largest generator available.
Shop Briggs & Stratton Standby Generators
Once you've determined how your backup power will be transferred and estimated the electrical loads you need to support, the next step is selecting the right generator capacity.
Shop Briggs & Stratton Standby Generators at AC Units For Less to compare residential and commercial backup-power options across multiple capacities, voltage configurations, and applications.
Not sure what size you need?
Start with our 13kW vs 18kW vs 22kW vs 26kW Standby Generator Guide before choosing your system.
For commercial properties with significant heating and cooling loads, also review our Standby Generator Sizing Guide for Commercial HVAC Equipment.
Frequently Asked Questions About Generator Interlocks and Transfer Switches
Is a Generator Interlock the Same as a Transfer Switch?
No.
Both are designed to prevent generator power and utility power from supplying the electrical system simultaneously, but they accomplish this differently.
A manual transfer switch typically supplies designated circuits through transfer equipment. An approved interlock uses a mechanical arrangement at the main electrical panel to prevent the main breaker and generator breaker from being on simultaneously.
Can an Interlock Kit Power My Whole House?
An interlock can potentially make generator power available to circuits in the main panel, but that does not mean your generator has enough capacity to operate every circuit simultaneously.
Generator capacity still determines what equipment can be operated.
Can I Connect a Portable Generator Directly to My Electrical Panel?
A generator connection to a home's electrical system should use properly designed transfer equipment, overcurrent protection, wiring, and inlet equipment as required for the installation.
Never improvise a generator connection or attempt to energize a home's electrical system by backfeeding through an appliance receptacle.
Can a Generator Run a Central Air Conditioner?
Potentially.
The generator must have sufficient capacity for the HVAC system's operating and starting requirements while also supporting any other loads operating simultaneously.
Central air-conditioning equipment can have significant compressor starting requirements, making generator sizing particularly important.
What Size Generator Do I Need to Run Central AC?
There isn't one generator size that works for every central air-conditioning system.
Generator requirements depend on the HVAC equipment's voltage, electrical specifications, compressor starting requirements, and other loads that need to operate simultaneously.
For commercial applications, consult the AC Units For Less Commercial HVAC Generator Sizing Guide.
Is a 30-Amp or 50-Amp Generator Better for Home Backup?
It depends on the generator and the loads you intend to operate.
A 50-amp connection can support greater current than a 30-amp connection when the generator and complete installation are designed for it, but the generator's actual rated output remains the controlling factor.
What Size Standby Generator Do I Need?
Start by determining which appliances and systems need backup power and calculating their operating and starting requirements.
Common residential standby generator capacities include 13kW, 18kW, 22kW, and 26kW.
Read our 13kW vs 18kW vs 22kW vs 26kW Standby Generator Guide for a closer comparison.
Is a Standby Generator Better Than a Portable Generator?
They serve different needs.
Portable generators can provide temporary emergency power and can be practical when only selected loads need electricity.
Standby generators are permanently installed and can provide a more automated backup-power solution when paired with appropriate transfer equipment.
The better configuration depends on your required loads, budget, outage frequency, property, fuel availability, and desired level of automation.
Do I Need an Electrician to Install a Generator Transfer Switch or Interlock?
Generator connections involve service panels, circuit breakers, grounding, neutral configuration, wiring, and potentially high electrical current.
Installation should comply with manufacturer requirements and applicable electrical codes. A qualified electrician can determine the appropriate configuration for your home and generator.
Build a Backup Power System Around Your Actual Needs
The generator interlock kit vs transfer switch decision isn't simply about choosing one piece of electrical hardware over another.
It's about deciding how you want to manage your home's backup power.
A manual transfer switch provides a more predetermined approach by supplying selected circuits. An interlock provides greater circuit flexibility but requires more active load management.
Before purchasing equipment:
- Identify the circuits you need during an outage.
- Determine their running and starting requirements.
- Consider whether your HVAC system needs backup power.
- Determine the appropriate generator capacity.
- Decide whether portable or standby power better matches your needs.
- Have a qualified electrician evaluate the electrical connection and transfer equipment.
If you're ready to explore permanent backup power, shop Briggs & Stratton standby generators from AC Units For Less and compare residential and commercial options based on the capacity and application your property requires.
