Generator Starts but the House Has No Power

A running standby generator may leave the house unpowered because it is performing a normal no-load exercise, its generator breaker is open, the automatic transfer switch did not transfer, or a fault interrupted power delivery. Engine sound alone cannot identify which condition exists.

First ask: exercise or actual utility outage?

Most routine exercise cycles start the engine without transferring the home. If utility power is available and the house remains on utility, that can be normal. Review the controller status and programmed exercise behavior before treating it as a failure.

During a real utility outage, note whether the whole property is dark or only selected circuits. An essential-circuit installation intentionally leaves non-backed-up circuits off, and managed loads may be delayed or shed.

Visible checks that do not require opening the transfer switch

1. Read the controller and save any alarm or warning.
2. Confirm the generator is not simply exercising.
3. Check the accessible generator main line circuit breaker position against the owner’s manual.
4. Look for a tripped backed-up branch circuit at the normal panel only if conditions are dry and safe.
5. Note whether any circuits powered briefly and then dropped out.

Generac describes the main line circuit breaker (MLCB) as the generator disconnect that interrupts output to protect against overload. If it is left OFF after service, the generator can run without sending power to the home. See Generac’s MLCB function and model-location guide. Do not repeatedly reset a breaker that trips again.

What can stop automatic transfer

• The controller is not in the required automatic state.
• The generator MLCB is open or tripped.
• The automatic transfer switch did not receive or complete its command.
• Utility-sensing or control wiring has a fault.
• The transfer switch or service equipment has an electrical problem.
• An overload or managed-load condition removed some or all intended loads.

On applicable systems, Generac says N1 and N2 conductors report utility loss and restoration. Those sensing circuits are part of automatic operation; they are not owner troubleshooting points inside energized equipment.

Do not open or force the transfer switch

An automatic transfer switch can contain utility power even while the neighborhood appears dark. Keep covers and the dead front in place. Generac’s manual-transfer procedure begins with disconnecting power sources and warns against transferring under load. Its instructions are equipment-specific and carry an electrocution warning.

For a homeowner who has not been trained on the installed switch, a failed automatic transfer is a service call. Do not move contacts with a tool, bridge terminals, or connect the generator to a receptacle.

What to tell the technician

• Utility outage start and whether neighbors also lost power.
• Controller status, code, and whether the engine stayed running.
• Generator MLCB position and whether it was tripped.
• Which circuits powered, which did not, and whether power appeared briefly.
• Any recent maintenance, electrical work, surge, flooding, or new high-demand load.

If an alarm stopped the engine, use the error-code guide. If the engine never started, use the no-start guide. During an extended outage, do not let transfer troubleshooting replace the required run-hour and oil checks.