Solar energy in Nagano, Japan
Average irradiation 3.79 kWh/m²/day · ~1107 kWh per kWp per year
Monthly solar irradiation & temperature in Nagano (NASA POWER)
| Month | Irradiation (kWh/m²/day) | Avg temp (°C) | Est. production per kWp (kWh) |
|---|---|---|---|
| Jan | 2.31 | -4.5 | 56 |
| Feb | 3.11 | -3.4 | 76 |
| Mar | 3.99 | 0.7 | 97 |
| Apr | 4.87 | 7.2 | 118 |
| May | 5.36 | 13.5 | 130 |
| Jun | 4.88 | 17.8 | 119 |
| Jul | 4.60 | 21.9 | 112 |
| Aug | 4.75 | 22.6 | 116 |
| Sep | 3.84 | 18.2 | 93 |
| Oct | 3.14 | 11.6 | 76 |
| Nov | 2.55 | 5.1 | 62 |
| Dec | 2.10 | -1.0 | 51 |
Solar potential of Nagano explained
Nagano receives an average of 3.79 kilowatt-hours of solar energy per square metre per day, measured over four decades of satellite observation. In practical terms, every kilowatt-peak of installed PV capacity yields about 1107 kWh of electricity per year here, assuming a well-oriented system with a typical 80% performance ratio. This is a solid mid-range solar resource: production is meaningful year-round, though winter output drops noticeably.
Frequently asked questions
Is solar worth it in Nagano?
With 3.79 kWh/m²/day of average irradiation, a 1 kWp system in Nagano produces roughly 1107 kWh per year. That is a good solar resource; with current panel prices most systems pay back well within their lifetime.
How much electricity would a 5 kW system produce in Nagano?
Approximately 6,000 kWh per year — enough to cover a large share of a typical household's consumption.
What data is this based on?
Long-term satellite observations from NASA POWER (1981–present) and the PVGIS SARAH3 database, assuming a performance ratio of 80%.
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