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UPS battery backup

Minutes: ride through a flicker, or shut down cleanly.

Portable power stations

Hours: a charged battery, with no fuel to store.

Portable generators

Days: as long as the fuel lasts, always outdoors.

Guide 90 · Transfer switch

Load Shedding Modules for an Automatic Transfer Switch: Do You Need Them?

Load shedding modules let an automatic transfer switch turn off big appliances when your generator nears its limit, then turn them back on when there is room. You need them if your switch powers the whole house and your generator cannot run every large load at once. If it can, or if you choose circuits yourself, you can skip them.

Updated Drafted and checked with AIFact-checked by the HoldBackup editorial team How this guide was made

On this page
  1. What load shedding does
  2. When you need load shedding modules
  3. When you can skip them
  4. How to check whether your generator can keep up
  5. What to check before buying modules
  6. Safety and installation
  7. Sources

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The verdict

Buy load shedding modules made for your automatic transfer switch's controller when your generator's running rating falls short of your large loads combined; if you would rather pick circuits yourself, a circuit-based kit like the Reliance Controls Pro/Tran 10-circuit kit may be simpler.

See the store link

What we check

  • Made for your transfer switch brand and controller
  • Number of priority levels you can set
  • Relay type that matches the load: 240-volt contactor or thermostat control
  • Contactor amp rating at or above each appliance's rating
  • Reconnect delay before loads come back on
  • Installed and permitted by a licensed electrician
Standby generator: louvered weatherproof cabinet on a concrete pad with clearance from the house wall, a lit status light, and a conduit run across the setback to a wall box

Drawing of backup power equipment.

Store link Transfer switch

Reliance Controls 31410CRK Pro/Tran 10-Circuit 30 Amp Generator Transfer Switch Kit,Gray

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Generator safety: carbon monoxide and backfeed

Carbon monoxide: never run a generator indoors, in a garage, basement or crawlspace, or near windows, doors or vents. Using a generator indoors can kill you in minutes. Use battery-powered carbon monoxide alarms in the home. CPSC Safety Alert 5123

Backfeed: never plug a generator into a wall outlet or a dryer outlet. That is extremely dangerous: it can energize utility lines and injure line workers and people in the home. Use a transfer switch or interlock installed by a licensed electrician. CPSC Safety Alert 5123 (PDF)

What load shedding does

When the power goes out, a whole-house automatic transfer switch connects your entire panel to the generator. Nothing stops the water heater, dryer, range, and air conditioner from all starting at once. If their combined draw passes what the generator can supply, the generator can stall or trip its breaker, and the whole house goes dark again.

Load shedding prevents that. The transfer switch controller watches the generator. When it sees the generator nearing its limit, it switches off the loads you ranked lowest. When the load drops, it brings them back one at a time.

The modules are the parts that do the switching. Common types, such as Generac's, are a contactor that cuts power to a large appliance circuit, or a relay that interrupts the thermostat call so the air conditioner simply stops asking to run.

When you need load shedding modules

You likely need them if you have a service-rated automatic transfer switch that feeds your whole panel and a generator smaller than your total household load. In that setup, the modules are what keep the large appliances from overloading the generator.

Some local codes, often based on National Electrical Code section 702.4, require the generator to cover the full calculated load unless an approved load management system is installed. The NEC is a paid NFPA document, so this is a summary, not a quote. Your electrician and local inspector decide what applies to your home, so ask before you settle on a generator size.

  • Central air conditioner or heat pump
  • Electric water heater
  • Electric dryer
  • Electric range or oven
  • Well pump, if it shares the generator with other large loads
  • Any other large appliance on its own circuit

When you can skip them

You can skip load shedding if your generator's running rating covers every load in the house running together. Your electrician can do this load calculation for you.

You can also skip it if your transfer switch only feeds a set of selected circuits. You pick the circuits during installation and control what runs during an outage. The listing on this page, the Reliance Controls Pro/Tran 10-circuit kit, is a transfer switch kit built around a set number of circuits. Check its spec sheet to confirm whether it is manual or automatic and that its amp rating suits your generator and your panel.

With a circuit-based switch, you are the load manager. Keep a written list of which circuits you can run together, and start the largest load first before adding others.

How to check whether your generator can keep up

Find the running watts and starting watts for your generator on its spec sheet. They are separate numbers, and the starting figure only lasts a moment.

Then find each large appliance's rating on its nameplate or in the maker's manual. For a closer look at plug-in loads, a plug-in watt meter shows what a device draws.

For example, if your generator's running rating is 12,000 watts and your air conditioner, water heater, and dryer add up to 15,000 watts on their nameplates, the generator cannot run all three together. Load shedding or careful circuit choice would be needed. Use your own numbers, and have your electrician confirm the math, since motor starting loads add to the picture.

What to check before buying modules

Load shedding modules are not universal. Many are built for one maker's transfer switch or generator, and sometimes only for certain models. Start with your transfer switch manual and the maker's list of compatible accessories.

  • Compatibility with your exact transfer switch model and controller
  • How many priority levels the system supports, so your most important loads shed last
  • Contactor amp rating, which must meet or exceed the appliance circuit it controls
  • Whether a thermostat module works with your type of thermostat wiring
  • A reconnect time delay, so loads do not cycle on and off rapidly
  • The warranty terms, including whether professional installation is required to keep it

Safety and installation

Transfer switches and load shedding modules connect to your home's wiring. A licensed electrician should install them, and most areas require a permit and inspection.

Do not assume any generator, cord, or inlet suits a given transfer switch. The generator outlet, the inlet, the cord, the voltage, and the transfer equipment all have to match the installation. Check the outlet type with your electrician before you buy anything.

Never run a generator indoors, in a garage, or near windows, doors, or vents. Generator exhaust contains carbon monoxide, which can build up quickly. Use carbon monoxide alarms inside your home.

Sources

Recorded AI check: Oct 9, 2026. The sources below may include later additions. AI checks compare factual numbers and checkable claims with web sources; they do not verify every statement.

Best inverter generator for a home outage compares units from the makers' numbers. Every guide in this class is in Portable generators.

How this guide was made

  1. Drafted and checked with AI. An AI model wrote the draft from the guide's topic. A second AI pass looked for factual numbers to check against web sources. This does not verify every statement. A draft that fails the check is held for review.
  2. Fact-checked by the HoldBackup editorial team. On , a person on the HoldBackup editorial team reviewed this guide against its sources. That is a review of the writing, not a test of any unit.
  3. General guidance only. No prices, rankings, or test results, because we have none to back them. Check any number against the maker's own spec sheet.
  4. No lab tests, and we say so. HoldBackup has not run any unit named here.
  5. The store link is not a pick for this guide. It goes to a unit in this product class that this guide does not review. Check it against the list above before you buy.
  6. Labelled store links. A store button goes straight to Amazon with HoldBackup's affiliate tag. HoldBackup counts the click. A live button carries a "paid link" label, and the disclosure sits above the first one on every guide.

Questions

Can I add load shedding to an automatic transfer switch I already have?

Often, yes, if the maker offers modules for your switch's controller. Check your transfer switch manual or the maker's accessory list for your exact model. If your controller does not support it, your electrician may suggest a separate load management system or a different switch.

Does load shedding work with a manual transfer switch?

Load shedding is a feature of automatic systems. With a manual or circuit-based transfer switch, you choose which circuits run and manage the load yourself. Confirm on the spec sheet whether a given kit is manual or automatic.

Will load shedding hurt my air conditioner?

A properly installed system should not, but check that the module includes a reconnect delay so the compressor is not switched on and off rapidly. Thermostat-control modules stop the system by interrupting the thermostat call rather than cutting power mid-run. Ask your electrician and check your HVAC maker's guidance.

Is load shedding a substitute for a properly sized generator?

It is a way to run a smaller generator safely, not a way to get more power from it. Shed loads stay off until there is room, so you will not run everything at once. If you want all appliances available together, size the generator to cover your full load.

Where does the price button go?

Straight to Amazon. Amazon sets the price and availability, and both can change.

More guides

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