Load shedding
Load shedding is automatically dropping lower-priority circuits when generator demand approaches capacity — letting a smaller standby generator protect a whole panel by making sure the air conditioner and dryer never run at the same time.
Standby systems implement it with smart management modules on selected circuits (typically the AC condenser, water heater, dryer, or EV charger): when frequency or load signals stress, the module drops its circuit and restores it when headroom returns.
This is why a 14 kW generator can legitimately back a 200 A panel: the load calculation counts managed loads differently. It is also the honest answer to “can I run everything?” — yes, just not simultaneously.
| Code basis | NEC 702.4(B) — an optional standby source may be sized to the load an automatic load-management system will allow, not the full connected load |
|---|---|
| Typically managed circuits | Air-conditioning condensers, electric water heater, electric dryer, EV charger, pool pump |
| Smart management modules | Usually rated 50 A at 240 V, one per circuit; controllers commonly handle four to eight |
| Effect on sizing | A 14–18 kW generator can back a 200 A panel that would otherwise call for 22–26 kW |
| Restore behaviour | Circuits return automatically in reverse priority after a settable delay, usually a few minutes |
| Cost | Roughly $150–$300 per module plus installation, against $1,500–$3,000 for the next generator size up |
Two different things are called load shedding
The utility meaning is a grid operator deliberately cutting power to blocks of customers to keep demand inside available generating capacity — the rolling blackouts Texas saw in February 2021, the rotating outages California uses in heat waves, and the scheduled daily outages that are routine in South Africa and parts of South Asia. In that version you are on the receiving end and there is nothing to configure.
The generator meaning, which is what this page covers, is the same principle applied inside your own installation: a control system that disconnects selected circuits so the generator is never asked for more than it can produce. Drop the least important loads first, keep the source inside its rating, and restore them when there is headroom again.
A third relative is worth naming because the hardware overlaps. Utility demand-response programmes pay you to let the utility cycle your air conditioner, water heater, or EV charger during peak periods, using smart panels, controllable breakers, and connected thermostats that look very much like generator load management. The difference is the trigger — a price or grid signal rather than a generator approaching its limit.
How the hardware decides what to drop
The common implementation is a smart management module: a relay in a small enclosure wired in series with one 240 V circuit, typically rated 50 A, carrying a priority number set at installation. The generator’s controller watches output — usually through current transformers, sometimes by sensing the frequency droop as the engine is loaded — and when demand approaches the limit it opens the lowest-priority module, pauses, and sheds the next one if that was not enough. As load falls the modules reconnect in reverse order after a delay, so a compressor is never restarted into a short cycle.
Air conditioning gets special handling because it is simultaneously the largest load and the one people least want to lose. Some controllers do not simply drop it: they permit one condenser at a time in a two-system house, or hold the compressor off while allowing the indoor blower to keep circulating air, or coordinate with a communicating thermostat so the house sheds gradually rather than in one lump.
Whole-panel smart electrical panels are the newer approach. Rather than a handful of relays on chosen circuits, every branch breaker is individually controllable and the panel does the arithmetic continuously — including for solar and battery storage. It is far more flexible and considerably more expensive, and it moves the load calculation into software that has to be configured correctly and keep working when the house is dark and the network is down.
Why it changes which generator you buy
NEC 702.4(B) sets the capacity rule for optional standby systems. The default is that the source must carry the load intended to be operated at one time. Where an automatic load-management system is installed, the code permits sizing to the load that system will actually allow to be connected — which is what makes a 14 kW generator on a 200 A service a legitimate design rather than an optimistic one.
The arithmetic that matters is the unmanaged total. Add up everything that must run without anyone thinking about it: furnace or boiler, refrigeration, well pump, sump pump, lighting, receptacles, network gear, medical equipment. That number is the generator’s floor. Then decide which large loads you will accept being interrupted and how gracefully. A managed electric water heater is invisible — a 50-gallon tank holds heat for hours. A managed EV charger is invisible. A managed central air conditioner in July is not invisible, and that is the tradeoff households discover after the install rather than before it.
On cost, modules usually win. Each one runs roughly $150–$300 plus labour; stepping a standby generator from 14 kW to 22 kW typically adds $1,500–$3,000 in equipment plus a larger gas line and sometimes a meter upgrade. The exception is when the managed load is the reason you bought backup power in the first place. If the requirement is medical equipment plus air conditioning in a hot climate, buy the capacity and manage nothing.
Doing it manually on a portable
A portable generator feeding a panel through an interlock or a manual transfer switch has no automation. You are the load-management system, which works, but only while someone is home and awake. Turn the large breakers off before you transfer, bring loads on one at a time starting with the biggest motor, and keep the continuous total under roughly 80% of the generator’s running rating so there is surge headroom left.
In practice this becomes a rota rather than a simultaneity problem. The well pump and the water heater run while the space heaters are off; then they swap. Laundry happens in the morning while nothing else large is on. That is the honest version of “can I run everything?” — yes, in shifts, and the shifts are the work.
Frequently asked questions
What is load shedding on a generator?
It is automatic disconnection of selected low-priority circuits when generator demand approaches capacity. A controller watches the generator’s output and opens relays on circuits like the air conditioner, water heater, dryer, or EV charger, then restores them once there is headroom again. The effect is that a generator smaller than the service can back the whole panel, because it is never asked to run every large load at once.
Can a 14 kW generator run a whole house?
With load management, usually yes for a typical house — and NEC 702.4(B) explicitly allows sizing to the managed load rather than the full connected load. What it cannot do is run central air, an electric range, an electric dryer, and an electric water heater simultaneously. Those get managed, meaning the generator serves them in turn. If the house has electric heat, two air-conditioning systems, or an EV that must charge during outages, 14 kW is not enough regardless of management.
Which circuits should be load-managed?
Loads that are large, intermittent, and tolerant of a delay: electric water heater, electric dryer, EV charger, pool or spa pump, a second air-conditioning system, and often the main condenser. Do not manage the furnace, refrigeration, well pump, sump pump, lighting, or anything medical — those belong in the unmanaged total that sets the generator’s minimum size.
Is load shedding the same as a rolling blackout?
They share a name and a principle but not a scale. A utility sheds load by cutting power to whole neighbourhoods when grid demand exceeds supply. A generator sheds load by dropping a few circuits inside one house so the engine stays inside its rating. If you searched for load shedding because your grid does it on a schedule, the generator meaning is what a backup system does to protect itself.
Do portable generators have load shedding?
Not automatically. Automatic load management is a standby-system feature — it needs a controller that can see generator output and relays it can operate. With a portable you shed manually: keep the large breakers off, add loads one at a time, and watch a wattmeter. Some manual transfer switches include wattmeters on both legs, which is the closest a portable setup gets.