20 kW home standby generators

Published October 3, 2026.

One air-cooled Guardian sheet, the 20 kW column. The house list under it is this site's formula, not a Generac load study.

Quick answer: On Generac's 16/20/22 kW Guardian spec sheet, models G007038-1 and G007039-1 are the 20 kW, 60 Hz units. Rated maximum continuous power is 20,000 watts on LP and 18,000 watts on natural gas. A 4-ton air conditioner at the top of Champion's band, plus Honda's electric dryer and an Energy Star fridge, produces a 16,500 W recommendation on this site. That buy number is under both of those continuous ratings. The sheet says this rating has no overload capability.

What the 20 kW column prints

The sheet's generator table has three columns: 16 kW, 20 kW, 22 kW. These figures are the middle column.

Row	20 kW column
Models	G007038-1, G007039-1 (aluminum, bisque), 60 Hz
Continuous power, LP / natural gas	20,000 W / 18,000 W
Rated voltage	240
Continuous load current at 240 V, LP / NG	83.3 A / 75.0 A
Main line circuit breaker	90 amp
Unit weight	448 lb / 203 kg
Dimensions (L × W × H)	48 × 25 × 29 in (121.9 × 63.5 × 73.7 cm), shared across the three columns
Sound at 23 ft (7 m), normal load	67 dB(A)
Quiet-Test low-speed exercise, same distance	55 dB(A)
Total harmonic distortion	Less than 5%

20,000 / 240 = 83.3 A, and 18,000 / 240 = 75.0 A, which is how the current row lines up with the two watt ratings. The 16 kW column is 16,000 W on both fuels. The 22 kW column is 22,000 W on LP and 19,500 W on natural gas. Shopping "20 kW" off the LP line and then connecting natural gas is an 18,000 W machine on this sheet.

The rating note says maximum kilovolt amps and current are limited by fuel Btu content, temperature, altitude, and engine condition, and that no overload capability is available for this optional-standby rating. A portable that advertises a surge above its running watts is a different kind of number. This sheet does not give the 20 kW unit a surge rating above 20,000 W on LP or above 18,000 W on natural gas.

Fuel consumption on the sheet, not the portable rule

The same column prints liquid-propane consumption as 87 ft³/hr (2.37 gal/hr) [8.99 L/hr] at 1/2 load and 130 ft³/hr (3.56 gal/hr) [13.48 L/hr] at full load. Natural gas is 204 ft³/hr (5.78 m³/hr) at 1/2 load and 301 ft³/hr (8.52 m³/hr) at full load. The sheet says to size the fuel pipe for full load. Required pressure at the generator fuel inlet, at all load ranges, is 3.5–7 inches water column for natural gas and 10–12 inches water column for LP gas.

Generac's note on that table: for Btu content, multiply ft³/hr × 2,500 (LP) or ft³/hr × 1,000 (natural gas). Full-load LP is 130 × 2,500 = 325,000 Btu/hr. Full-load natural gas is 301 × 1,000 = 301,000 Btu/hr. Those multiplications are the sheet's instruction. They are not EIA's Btu factors, and they are not this site's 1.37 propane multiplier. The portable gasoline rule is walked on how much propane a generator uses. Do not divide 3.56 gal/hr by 1.37 and call the result this generator's gasoline burn. The sheet does not print a gasoline rate.

The sheet also does not say that "full load" is any particular house. 3.56 gal/hr is the 20 kW unit at the load Generac used for that row.

Worked example: dryer, 4-ton air, fridge

Three published rows, all on together, headroom 20%. Champion lists a 4-ton central air conditioner at 4,000–5,000 running watts and 6,500–8,000 starting watts. This case uses the top of that band, 5,000 W running and 8,000 W starting, the same way the food-truck page uses the top of a range. Honda lists an electric dryer at 6,750 starting watts and 5,400 running watts, marked 240 V, and an Energy Star fridge at 1,200 starting watts and 132–192 running watts. This case uses 192 W for the fridge.

Running total = 5,000 + 5,400 + 192 = 10,592 W.
Largest start is the air conditioner at 8,000 W, above the dryer's 6,750 W. Extra surge = 8,000 − 5,000 = 3,000 W.
Peak = 10,592 + 3,000 = 13,592 W.
13,592 × 1.20 = 16,310 W, rounded up to the next 500 W = 16,500 W recommended.

16,500 W is under the sheet's 18,000 W natural-gas continuous rating and under the 20,000 W LP rating. The peak of 13,592 W is under both as well. On this one list, the 20 kW column's continuous ratings cover the buy number and the peak. The 16 kW column is 16,000 W continuous on both fuels, which is under the 16,500 W recommendation and over the 13,592 W peak. Headroom is the whole difference. Replay the three rows on the calculator. The dryer-and-range pair that lands at 11,000 W, without the air conditioner, is already on backup generator installation.

Altitude on the sheet's own rate

The rating footnote says maximum power decreases approximately 3.5% for each 1,000 feet above sea level, and also approximately 1% for each 10°F above 60°F. At 5,000 feet the altitude sentence alone is 5 × 3.5% = 17.5%. Applied to the sea-level maximums, LP is 20,000 × (1 − 0.175) = 16,500 W, and natural gas is 18,000 × (1 − 0.175) = 14,850 W. That arithmetic uses only the altitude sentence. It is not a combined heat-and-altitude figure, and it is not the result button on altitude derate. That tool exempts the first 1,000 feet and starts its heat term at 77°F. Those thresholds are the script.

After that 17.5% cut, the LP figure equals this page's 16,500 W recommendation, and the natural-gas figure, 14,850 W, is under the recommendation and still over the 13,592 W peak. A nameplate that covers the list at sea level can miss the headroom the formula asks for at 5,000 feet, while the peak itself still fits. The sheet says "approximately." It is not a site survey.

A common mistake

Treating the sheet's "as close as 18 in (457 mm) to a structure" as permission to park any generator 18 inches from a wall. The sheet says the unit is listed for that clearance, and the same footnote says it must be located away from doors, windows, and fresh air intakes and in accordance with local codes. That 18 inches is this enclosure's listing. It is not the portable-generator distance. CPSC still says a portable generator goes outdoors, at least 20 feet from homes and buildings. The 67 dB(A) figure is at 23 feet from the front of this set, at normal load. The distance button that turns 67 dB(A) into a farther reading is on noise at the lot line.

Limits, and when to call a pro

Installing this unit, the gas piping at the pressures above, and a transfer switch takes a licensed electrician and a permit where local code requires one. OSHA says not to attach a generator to a structure's electrical system unless a qualified electrician installs a transfer switch. The sheet's 200 A service-rated smart-switch table includes model G007039 (20 kW): 2 poles, 200 A, 120/240 V. The opening feature list also names a 100 A, 16-circuit switch as an option for the series. The 100 A table on the sheet is headed G007036 (16 kW), so this page does not assign that table's circuit count to the 20 kW models.

The sheet's exercise line is 5 minutes. Utility voltage sensing setpoints in the feature list are 65% dropout and 80% pickup. None of that replaces a load study. A dealer survey is Generac's own advice for standby sizing, linked from the one-appliance pages on this site. Compare a smaller diesel sheet on Kubota standby generator, and the portable-versus-automatic choice on portable vs standby.

Compiled with AI assistance from the sources below. Spot an error? Email [email protected].

Sources

Generac, 16/20/22 kW Guardian spec sheet (part no. 10000000194, rev. L)
Champion, Generator Wattage Chart — 4-ton central air conditioner row
Honda, What wattage generator do I need? — dryer and fridge rows
CPSC, generator carbon monoxide warning
OSHA 3286, Using Portable Generators Safely