Can I just use a 22 kW generator for any 2,000 sq ft house?

Not reliably. This example lands at 23.8 kW for whole-house backup with gas heat; the same footprint with electric heat needs more, and a house with gas cooking and laundry needs less. Run the calculation on the actual appliances.

Does a generator have to carry the air conditioner?

Only if it is on a backed-up circuit. Central air is usually the single largest motor load and the reason whole-house units are so much bigger than essentials units; many owners choose a load-managed setup that lets the air conditioner run when the rest of the house is quiet.

Is the calculated load what the generator will actually see?

No. The Article 220 figure is a code sizing load with demand factors built in; real draw is usually lower. The code requires the generator to be able to carry the calculated load, not to run at it continuously.

A portable generator through a manual transfer switch or interlock is an essentials setup: 11.7 kW here, which is at the top of what large portable units deliver. Whole-house backup at 23.8 kW is standby territory.

GeneratorsCalculated per NEC 2023

What size generator do I need for a 2,000 sq ft house?

For a 2,000 ft² house with a gas furnace, an electric range, dryer and water heater, and a 3-ton air conditioner, the NEC 220.82 optional calculation comes to 23,840 VA, or 23.8 kW. A generator that carries the whole house through a standard transfer switch needs to cover that, which means the 26 kW standby class. If you only back up lights, receptacles, the refrigerator and the furnace blower, the essentials load is 11.7 kW, a 14 kW unit. The square footage by itself decides very little; the electric appliances do.

Updated September 23, 2026. Numbers on this page are computed by the same engine as the calculators, under NEC 2023.

Worked example: 2,000 ft² house, gas heat, electric kitchen and laundry

Calculated per NEC 2023

Optional method (220.82)

Inputs

NEC edition	NEC 2023
Floor area	2,000 ft²
Small-appliance circuits	2
Laundry circuits	1
Cooking	Electric range 12 kW
Clothes dryer	5,000 VA
Appliances fastened in place	Electric water heater 4,500 VA; Dishwasher 1,200 VA; Garbage disposal 900 VA; Built-in microwave 1,500 VA
Heating	Gas or none (no electric heating load)
Air conditioning	3,600 VA

Result

Calculated load	23,840 VAfrom 39,200 VA connected
Calculated current	99.3 Aat 240 V
Minimum service rating	100 A240.6(A) standard rating, not less than 100 A
Whole-house generator	26 kW classFull calculated load 23,840 VA; NEC 702.4(B)(2)(a)
Essentials-only generator	14 kW classLighting and receptacle circuits 10,500 VA at the optional-method demand, plus 1,500 VA refrigerator and furnace allowance

Line item	NEC	Connected	Demand	Basis
General lighting and receptacles	220.82(B)(1)	6,000 VA	(in subtotal)	2,000 ft² × 3 VA/ft²
Small-appliance and laundry circuits	220.82(B)(2)	4,500 VA	(in subtotal)	3 circuits × 1500 VA
Appliances fastened in place	220.82(B)(3)	8,100 VA	(in subtotal)	4 at nameplate
Ranges, ovens and cooking units	220.82(B)(3)	12,000 VA	(in subtotal)	1 at nameplate
Clothes dryers	220.82(B)(3)	5,000 VA	(in subtotal)	1 at nameplate
Permanently connected motors	220.82(B)(4)	—	(in subtotal)	None
Other fixed loads	220.82(B)(3)	—	(in subtotal)	None
EV supply equipment	220.82(B)(3)a	—	(in subtotal)	None
General load after demand factors	220.82(B)	35,600 VA	20,240 VA	First 10,000 VA at 100%; remaining 25,600 VA at 40% = 10,240 VA
Electric space heating	220.82(C)	—	0 VA	None
Air conditioning and cooling	220.82(C)(1)	3,600 VA	3,600 VA	100% of 3,600 VA; largest selection

The whole-house figure is the full calculated load, 23.8 kW, so the next standby class up is 26 kW. Dropping the range, dryer, water heater and air conditioner from the backed-up circuits leaves 11.7 kW, which a 14 kW unit covers.

Generator classes are typical residential standby ratings; confirm with the manufacturer’s specification sheet.
A whole-home transfer switch without load management must carry the full calculated load (NEC 702.4(B)(2)(a)).
The essentials figure assumes a limited transfer switch or load-managed circuits for lights, receptacles, refrigerator, furnace blower and pumps only.

Why the answer comes in two sizes

NEC 702.4(B) is the rule that decides which number applies. If the transfer switch can connect the generator to the entire house with no load management, the generator must be able to carry the full calculated load from Article 220, the same calculation used to size the service. If the transfer switch only feeds selected circuits, or a load-management system sheds the big appliances when the generator is near its limit, the generator only has to carry those selected loads.

That is why the same house produces 23.8 kW on one framing and 11.7 kW on the other. The gap between them is the range, dryer, water heater and air conditioner, which together account for most of the 39,200 VA of connected load in this example.

What the classes mean

Residential standby generators are sold in a handful of classes: 7.5, 10, 14, 18, 22, 26, 30, 38, 48, 60 kW. Air-cooled units stop around 26 kW; above that you are into liquid-cooled equipment with a different price and footprint. The calculator picks the smallest class at or above the required kW; it does not add a "growth" margin, so if you plan to add an EV charger or a heat pump later, size for that house instead of this one.

Nameplate kW is the continuous rating on natural gas or propane. Many units are rated slightly lower on natural gas than on propane, and derate at altitude and in heat. Confirm the specification sheet before buying.

What would change the number

Re-run the estimator with your own appliances; these are the inputs that move the result most:

Electric heat. A 10 kW heat strip or 15 kW of baseboard replaces the 3,600 VA air conditioner in the calculation and pushes a 2,000 ft² house into the 30 to 38 kW classes for whole-house backup.
A gas range and dryer. Removing 17,000 VA of connected load from the general-load tier takes about 6.8 kW off the whole-house figure.
A well pump or sump pump. Pumps are added to the essentials figure at nameplate because they are the loads people most need during an outage.

Frequently asked questions

Can I just use a 22 kW generator for any 2,000 sq ft house?: Not reliably. This example lands at 23.8 kW for whole-house backup with gas heat; the same footprint with electric heat needs more, and a house with gas cooking and laundry needs less. Run the calculation on the actual appliances.
Does a generator have to carry the air conditioner?: Only if it is on a backed-up circuit. Central air is usually the single largest motor load and the reason whole-house units are so much bigger than essentials units; many owners choose a load-managed setup that lets the air conditioner run when the rest of the house is quiet.
Is the calculated load what the generator will actually see?: No. The Article 220 figure is a code sizing load with demand factors built in; real draw is usually lower. The code requires the generator to be able to carry the calculated load, not to run at it continuously.
Portable or standby?: A portable generator through a manual transfer switch or interlock is an essentials setup: 11.7 kW here, which is at the top of what large portable units deliver. Whole-house backup at 23.8 kW is standby territory.