The Pros and Cons of Generator Interlock Kits vs. Transfer Switches
When a storm hits in Missouri and the power goes out, having a backup generator is only half the equation. The real question is: how will that generator connect to your home’s electrical system safely and legally?
Two common methods are generator interlock kits and transfer switches. Homeowners often get confused trying to choose between them — especially when looking at YouTube DIY videos or budget options at big-box stores.
At Cain Electric, we’ve installed both solutions across homes in Wildwood, Pacific, Union, Washington, and Eureka. In this article, we’ll break down the differences, explain when each one makes sense, and help you decide what’s best for your home.
What Is an Interlock Kit?
A generator interlock kit is a mechanical device installed on your main breaker panel. It physically prevents the main utility breaker and the generator breaker from being on at the same time — which protects against dangerous backfeeding into the utility grid.
Interlock kits are:
- Installed directly on your main electrical panel
- Controlled using manual breaker switches
- Designed for use with portable generators
- A cost-effective option when used correctly
With an interlock kit, you connect your portable generator to your home using a generator inlet box (typically a 30A or 50A plug) wired to a dedicated breaker in your panel. Then, using the interlock, you manually switch between utility and generator power.
What Is a Transfer Switch?
A transfer switch is an independent switching device — either manual or automatic — that redirects your home’s power source between the grid and your generator.
There are two main types:
- Manual Transfer Switch (MTS): Requires you to flip the switch during an outage. Ideal for portable generators.
- Automatic Transfer Switch (ATS): Detects a power outage and switches to generator power automatically. Required for whole-home standby generators.
Transfer switches are usually mounted near your main panel or directly integrated into whole-home systems like Generac or Kohler setups.
See our generator installation services for Missouri homeowners.
Interlock Kits: Pros and Cons
✅ Pros:
- More Affordable: Kits and installation are significantly cheaper than transfer switches
- Simple Design: Fewer moving parts, easy to operate once installed
- Compact: Doesn’t require extra wall space — it’s installed on your main panel
- Flexible Loads: You can manually select which breakers to power based on generator size
❌ Cons:
- Manual Operation Only: You must be home to safely switch power
- Requires Access to Panel: Inconvenient during storms or at night
- Code Restrictions: Some Missouri municipalities don't allow interlocks or require specific labeling
- No Surge Protection: Typically lacks built-in surge or voltage regulation
- Can’t Power Entire Home Automatically
Best for: Budget-conscious homeowners with portable generators who are comfortable operating their panel manually during outages.
Transfer Switches: Pros and Cons
✅ Pros:
- Automatic Options Available: ATS units keep your power on without lifting a finger
- Code-Compliant: Preferred by inspectors and insurance providers
- Cleaner Install: Looks professional and integrates well with whole-home systems
- Safer for All Users: No panel access or manual circuit switching needed
- Can Power Essential or Entire Circuits Selectively
- Supports Larger Loads (especially with whole-house generators)
❌ Cons:
- Higher Cost: Equipment and installation are more expensive
- Takes More Space: Especially if using a subpanel-style transfer switch
- Less Flexible: MTS usually supports a fixed set of circuits unless upgraded
Best for: Homeowners investing in a standby generator, anyone who wants automatic switching, or those with frequent power outages.
Key Differences at a Glance
- Cost: Interlock kits are cheaper; transfer switches are a larger investment
- Automation: Only transfer switches offer automatic failover
- Safety: Transfer switches are generally safer and more compliant
- Code Approval: Transfer switches are universally accepted; interlocks depend on local rules
- Ease of Use: Transfer switches win for convenience — no manual breaker shuffling
Which One Does Code Require in Missouri?
While interlock kits are technically permitted in many parts of Missouri, they must meet specific criteria:
- UL-listed for your exact panel model
- Installed by a licensed electrician
- Clearly labeled with instructions
- Only used with portable generators
In contrast, transfer switches — especially automatic ones — are strongly preferred by code for whole-home generator systems and may be required for larger standby installations.
Cain Electric ensures your installation is safe, legal, and passes inspection in your specific city or county.
Our Take: What We Recommend
Choose an Interlock Kit if:
- You already own a portable generator
- You want to backfeed only selected circuits manually
- You’re looking for a lower-cost way to add emergency backup
- You’re comfortable operating breakers during an outage
Choose a Transfer Switch if:
- You’re investing in a whole-home standby generator
- You want the system to switch automatically when you’re not home
- You want a clean, professional installation
- You want peace of mind, especially for long-term outages
Cain Electric installs both systems — and we’ll help you choose based on your home, generator type, and long-term goals.
Learn more about our backup power solutions.
Don’t Let Confusion Delay Your Power Backup Plans
Interlock kits and transfer switches both have their place — but picking the wrong one can lead to safety issues, code violations, or unnecessary costs.
Cain Electric brings clarity to your generator setup. We’ll assess your electrical panel, confirm your generator specs, handle all permits and inspections, and make sure your family has reliable backup power all year long.
Serving Franklin County and surrounding Missouri communities including Wildwood, Pacific, Union, Eureka, and Washington.
