Sizing guide
Load management, or just buy the bigger generator?
Most homes that get quoted a large generator do not have a capacity problem. They have a simultaneity problem — too many big things trying to start in the same second. Those are different problems with very different prices.
The two questions people confuse
How much power does the house draw? is a steady-state question, and the answer is usually smaller than people expect. A large DFW home running two air conditioners, a refrigerator, lighting, networking and a pool pump is rarely pulling what its service size implies.
What happens when everything restarts at once? is a different question entirely. An air-conditioning compressor draws several times its running current for a fraction of a second at start. Two of them starting together is the single largest demand the house will ever place on a generator, and it lasts under a second.
Size for the second question with no management and you buy a machine that spends the entire outage at a quarter of its capacity, having been purchased for one instant that lasts half a second. That is where the money goes.
What intelligent load management does
The control watches the generator's available capacity and restores large loads only when there is room. When the first compressor starts, the second is briefly held. When the first settles into its running current, the second is released. From inside the house nothing observable happens — both air conditioners run, seconds apart instead of simultaneously.
Four things about the Cummins implementation are worth knowing:
| Property | What it means in practice |
|---|---|
| Integrated | Built into the generator. No separate panel, no additional hardware to buy or find wall space for. |
| Smart | The generator learns the load requirements and turns loads on only when it has capacity, rather than following a fixed priority list blindly. |
| Amperage-based, not frequency-based | It reacts to current demand rather than waiting for the engine to be dragged down. A frequency-based system by definition acts after the sag has started. |
| Up to four managed loads | Typically two AC compressors plus two of: range, pool pump, well pump, electric water heater. |
The amperage-versus-frequency distinction is the one technical point in this guide that is genuinely checkable against a competitor's own documentation, and it is the reason Cummins claims a faster response. It is not marketing about reliability. It is a statement about what the control is measuring.
What the choice actually costs
The decision usually presents itself at the top of the air-cooled range. A 20kW air-cooled unit with load management, against stepping into the liquid-cooled range at 25kW:
| Option | Equipment price |
|---|---|
| RS17A — 17kW air-cooled | $5,167.05 |
| RS20A — 20kW air-cooled | $5,747.50 |
| RS25 — 25kW liquid-cooled | $16,829.15 |
The equipment gap between the top air-cooled unit and the entry liquid-cooled unit is $11,081.65, and that is only the machine. Liquid-cooled units are heavier, need a larger pad, carry a shorter base warranty term, and cost more to install and to service. The real difference at the curb is considerably wider than the price table shows.
Against that, load management on the air-cooled range is integrated — there is no separate box to buy. A soft-start module on the largest compressor, which attacks the same problem from the other end by reducing the inrush itself, is a few hundred dollars.
This is why we price the soft start and confirm the load management configuration before agreeing to a larger generator. Doing it the other way around — sizing up first, then discovering the smaller unit would have carried the house — is the most expensive ordinary mistake in residential standby.
When load management is the right answer
Two air-conditioning systems in a house whose continuous draw is comfortably inside the generator's rating. This is the classic two-story Plano, Frisco or McKinney case, and it is the situation load management was designed for.
A single large compressor plus one other heavy intermittent load — a pool pump, a well, an electric range. These never actually need to run in the same second.
Any house where the sizing calculation lands just over a size boundary because of startup surge rather than running load.
When it is not
When the continuous load is genuinely too high. Load management sequences starts. It does not manufacture capacity. If the house needs more watts than the machine makes, all you get is a generator that shuffles loads for the whole outage.
When more than four loads need managing. Four is the limit on the air-cooled range. A house with three AC zones, a pool, a well and an electric range has exceeded it.
When nothing may ever drop. A home office with equipment that cannot tolerate being held back, medical equipment, a server rack. If a load must be continuously available, it should not be one of the managed ones — and if there are several of those, size for them.
When you want whole-house with no thinking. A legitimate preference. Say so and we will size for it. It is a decision to spend money for simplicity, which is fine — it should just be a decision rather than an accident.
How to settle it for your house
Start with the sizing calculator, which gives you a range in about two minutes without a phone number. Then read will a generator run my air conditioner, because in Texas the compressors decide this.
The final answer comes from the survey, where we count the actual loads, read the actual nameplates, and check the gas supply that has to feed whatever we land on. It takes about forty-five minutes and it costs nothing.
Questions
What is intelligent load management on a generator?
It is a control that watches what the generator can supply and restores large loads only when there is capacity for them. Instead of every air conditioner, oven and pump trying to start at once when the generator picks up the house, they come back in a managed order. The result is that a smaller generator can cover a house that would otherwise need a larger one.
Is load management the same as a load-shed relay?
Not quite. A plain load-shed relay simply disconnects a chosen circuit whenever the generator runs — you lose that load for the whole outage. Intelligent load management restores it as soon as there is headroom, so you usually get everything, just not all in the same instant.
Is Cummins load management better than Generac's?
On one specific and checkable point, yes. Cummins responds on amperage rather than frequency. A frequency-based system waits for the engine to be dragged down before it reacts, which means the sag has already happened. An amperage-based system sees the current demand and acts sooner. Whether that matters to you depends on how close to the edge you are sizing.
How many loads can it manage?
The Cummins air-cooled units handle up to four managed loads. In a typical two-story DFW home that is two air-conditioning compressors and two of the following: an electric range, a pool pump, a well pump, or an electric water heater.
Is it ever the wrong answer?
Yes. If the house genuinely needs more continuous capacity than the generator has — as opposed to needing help with simultaneous startups — load management does not create power that is not there. It smooths a start-up problem. It does not fix an undersized machine, and pushing it to do so produces a house that spends the outage rotating loads and satisfying nobody.
Load management behavior described here is from Cummins dealer documentation for the 13–20kW home standby range. Equipment prices are the published prices on this site and exclude installation.
Been quoted a bigger generator than you expected?
Bring the quote. If a soft start and load management cover it, we will tell you that, and it is the cheaper sale.