12 kW solar system: cost, output and payback
A 12 kW solar system is 30 panels and costs about $34,200 installed, or $23,940 after the US federal tax credit. Across 673 measured cities it produces a median of 15,769 kWh a year and pays back in about 12.9 years.
Check whether 30 panels fit your actual roof → These are medians across real cities; your roof's size, pitch and shading change the answer.
Is a 12 kW system the right size?
This is more than most households need. A 12 kW array covers roughly 146% of an average home's 10,800 kWh a year, so unless you have electric heating, an EV, a pool or unusually high usage, you would be exporting a large share of it — usually at well below the retail rate you paid to install the panels.
What a 12 kW system produces where you live
Output depends almost entirely on local sunlight. The same 12 kW of hardware produces 21,573 kWh a year in Palmdale and 9,731 kWh in Fairbanks — a 2.2× spread across 673 cities we have measured from Google's rooftop imagery.
Where a 12 kW system pays back fastest
Payback is driven more by electricity price than by sunshine. Honolulu, HI tops the list at 4.5 years on 42.1¢/kWh, while Gatineau, QC takes 38 years on just 7.9¢/kWh. That is identical hardware producing 28% less electricity, but taking 8.4× as long to pay for itself — because the power it displaces is worth 5.3× less.
| City | kWh/yr | Rate | Payback |
|---|---|---|---|
| Honolulu, HI | 18,227 | 42.1¢ | 4.5 yrs |
| Lihue, HI | 18,125 | 42.1¢ | 4.5 yrs |
| Kahului, HI | 16,595 | 42.1¢ | 4.6 yrs |
| Hilo, HI | 15,402 | 42.1¢ | 4.8 yrs |
| Kailua-Kona, HI | 12,781 | 42.1¢ | 5 yrs |
| Quincy, MA | 15,514 | 30.1¢ | 6.6 yrs |
| Boston, MA | 14,749 | 30.1¢ | 6.7 yrs |
| Worcester, MA | 14,719 | 30.1¢ | 6.8 yrs |
| Fall River, MA | 14,576 | 30.1¢ | 6.8 yrs |
| Lowell, MA | 14,504 | 30.1¢ | 6.8 yrs |
| Somerville, MA | 14,464 | 30.1¢ | 6.8 yrs |
| Cambridge, MA | 14,321 | 30.1¢ | 6.8 yrs |
| Lynn, MA | 14,198 | 30.1¢ | 6.8 yrs |
| New Haven, CT | 15,014 | 29.2¢ | 6.9 yrs |
| Newton, MA | 14,025 | 30.1¢ | 6.9 yrs |
Where it pays back slowest
| City | kWh/yr | Rate | Payback |
|---|---|---|---|
| Gatineau, QC | 13,168 | 7.9¢ | 38 yrs |
| Levis, QC | 13,525 | 7.9¢ | 37.7 yrs |
| Trois-Rivières, QC | 13,739 | 7.9¢ | 37.5 yrs |
| Longueuil, QC | 13,943 | 7.9¢ | 37.4 yrs |
| Drummondville, QC | 13,984 | 7.9¢ | 37.3 yrs |
| Terrebonne, QC | 14,076 | 7.9¢ | 37.3 yrs |
| Montreal, QC | 14,117 | 7.9¢ | 37.2 yrs |
| Laval, QC | 14,127 | 7.9¢ | 37.2 yrs |
| Quebec City, QC | 14,362 | 7.9¢ | 37 yrs |
| Winnipeg, MB | 14,168 | 10.1¢ | 29.1 yrs |
Other system sizes
12 kW solar questions
How many panels is a 12 kW solar system?
A 12 kW system is 30 panels at 400W each, the standard residential size in 2026. It needs roughly 60 m² (about 646 sq ft) of usable roof, and more in practice once you allow for edge setbacks, vents and access paths.
How much does a 12 kW solar system cost?
About $34,200 installed before incentives at $2.85 per watt, or roughly $23,940 after the 30% US federal tax credit. Quotes for the same 12 kW system routinely differ by thousands, because labour, margin and equipment vary far more than hardware cost does.
How much power does a 12 kW solar system produce?
Across the 673 cities we have measured, a 12 kW array produces a median of 15,769 kWh a year. The range runs from about 9,731 kWh in Fairbanks to 21,573 kWh in Palmdale — the same hardware, differing by 122% purely on local sunlight.
See the full dataset → every city, with sunlight, shading, roof size and rates.
Estimates generated 2026-08-22 from Google Solar API rooftop samples across 673 cities. Not a quote and not financial advice.