A sizing chart answers one question fast: which generator tier belongs on your shortlist. Here’s ours, with a rule you won’t find on other charts — every number is either verified against a manufacturer document or visibly marked unverified. Generac’s published home standby lineup runs 10kW to 28kW, and that lineup frames the tiers below. The tonnage each tier can start follows Generac’s published sizing guidance — including that its 22kW and 24kW are officially rated to start a five-ton compressor. The method behind the table lives in our sizing and fuel supply guide.
What does each size tier typically serve?
| Generator tier | HVAC it can start | Typical home profile | Fuel reality |
|---|---|---|---|
| 10kW | Essentials, not central AC | Refrigeration, lights, furnace blower, a window unit | Modest demand either fuel |
| 14kW | Up to ~2 tons | Essentials-plus for a smaller single-story; first tier where central AC enters the conversation | Modest demand either fuel |
| 18kW | ~3 tons | Mid-size home, selective coverage, or smaller whole-home with managed loads | Meter check worth doing in-city |
| 22kW | Up to 5 tons | The tier most North Alabama quotes lead with; whole-home candidate with load management | Meter check often decisive |
| 24kW | 5 tons, more margin | Whole-home for larger single-system houses | Meter check often decisive |
| 26kW | 5 tons + heavy loads | Whole-home headroom; dual-system and all-electric candidates | Meter upgrade question common in-city; propane burn rate matters |
Generac also publishes a 28kW model at the top of the range. Below 10kW you’re in portable territory, which is a different purchase for a different problem.
The profile column is a starting shortlist, nothing more. Your house earns its row from the load calculation, not from resembling a description.
How do you read a sizing chart without fooling yourself?
Treat it as a filter, not an answer. A chart can tell you a 10kW won’t start a 4-ton compressor and a 26kW is overkill for an essentials-only plan. It can’t see your LRA, your second HVAC system, your well pump, or the fact that your dryer and water heater are both electric. Two homes with identical square footage can need different generator sizes because their starting loads differ — which is why every square-footage-based chart eventually embarrasses somebody.
The tier you circle here is a hypothesis. The nameplate visit confirms it or kills it.
Where do the tonnage figures come from?
Generac’s published sizing guidance, not from another blog’s chart. Generac officially rates its 22kW and 24kW units to start a five-ton compressor, which anchors the middle of the table; the smaller tiers step down from there. Your own number still comes off your nameplates — a chart narrows the shortlist, it doesn’t replace the load calculation. If a chart elsewhere shows a confident figure with no source behind it, that’s worth a raised eyebrow.
How does fuel supply change what the chart tells you?
Every row assumes the fuel can keep up, and in this market that assumption fails regularly. In-city, each step up the chart raises the gas demand on a meter that also feeds your furnace and water heater — check the meter before you commit to a tier, because an upgrade changes the whole install plan. On propane, the chart reads differently: a bigger tier drains the tank faster, so tank size and runtime decide how much generator you can actually afford to feed. And if a mid-tier unit could cover your whole circuit list with load management, the honest move is usually down the chart, not up it.