Peak Sun Hours in Tokyo, Tokyo, Japan
- Solar zone
- Zone 2 (moderate)
- Best month
- May (5.1)
- Worst month
- December (2.5)
- Climate
- Temperate · 15.6°C
Monthly solar breakdown
| Month | GHI | Clear-sky | DNI | DHI | Temp °C | Humid % |
|---|---|---|---|---|---|---|
| Jan | 2.81 | 3.51 | 4.76 | 0.92 | 4.7 | 75 |
| Feb | 3.35 | 4.51 | 4.35 | 1.27 | 5.6 | 76 |
| Mar | 4.11 | 5.78 | 4.10 | 1.69 | 8.8 | 76 |
| Apr | 4.83 | 6.86 | 3.86 | 2.15 | 13.5 | 77 |
| May | 5.14 | 7.55 | 3.41 | 2.52 | 18.2 | 79 |
| Jun | 4.56 | 7.66 | 2.28 | 2.62 | 21.8 | 82 |
| Jul | 4.78 | 7.42 | 2.77 | 2.52 | 25.5 | 83 |
| Aug | 5.00 | 6.83 | 3.75 | 2.28 | 26.9 | 81 |
| Sep | 3.88 | 5.93 | 3.12 | 1.87 | 23.6 | 82 |
| Oct | 3.07 | 4.71 | 3.11 | 1.41 | 18.1 | 82 |
| Nov | 2.62 | 3.62 | 3.69 | 1.04 | 12.7 | 80 |
| Dec | 2.47 | 3.15 | 4.36 | 0.82 | 7.3 | 78 |
GHI, Clear-sky, DNI, DHI in kWh/m²/day. Data: NASA POWER climatology (long-term monthly averages).
Off-grid calculator
Add appliances
- Add an appliance to size a system.
Sizing
- Daily load
- 0.00 kWh
- Panel wattage
- 0 W
- Panel count (400W modules)
- 0
- Battery bank
- 0.0 kWh
Sizing against worst-month PSH of 2.47 kWh/m²/day, 0.77 system efficiency.
About solar in Tokyo
Tokyo, Japan has a temperate climate with meaningful seasonal variation in solar resource. Its annual peak sun hours average 3.89 kWh/m²/day, a moderate solar resource by global standards.
The strongest month in Tokyo is May (spring) at 5.14 kWh/m²/day, and the weakest is December (winter) at 2.47 kWh/m²/day. When sizing a year-round off-grid system, it's standard practice to design against the December value rather than the annual average — otherwise the battery bank runs low during the darkest weeks.
Given the moderate resource, Tokyo installations typically oversize panels or combine solar with another source (grid, generator, hydro) for reliability.
FAQ
- What are the peak sun hours in Tokyo?
- Tokyo averages 3.89 peak sun hours per day annually, ranging from 2.47 in December to 5.14 in May.
- How many solar panels do I need in Tokyo?
- Panel count depends on your daily load. At Tokyo's annual average of 3.89 kWh/m²/day, a 5 kWh/day load needs roughly 5 × 400 W panels. Use the calculator above for your actual load.
- What size battery do I need in Tokyo?
- Sizing against Tokyo's worst month (December, 2.47 kWh/m²/day) with 2 days of autonomy at 80% depth of discharge, a 5 kWh/day load needs about a 12.5 kWh battery bank.
- How does Tokyo's solar resource compare globally?
- Tokyo sits in solar zone 2 out of 5 (where 5 is strongest) at 3.89 kWh/m²/day — moderate by global standards. For reference, top-tier desert sites average ~6.5 and high-latitude cities around 2.5 kWh/m²/day.
- How much does winter reduce solar output in Tokyo?
- Tokyo's worst month (December) delivers 2.47 kWh/m²/day — about 48% of the summer peak of 5.14. Off-grid systems here typically oversize 1.5–2× or pair with a backup source.
- Do cloudy days significantly affect Tokyo's solar?
- Partly. Diffuse light still produces 10–25% of clear-sky output. Tokyo's 3.89 kWh/m²/day already reflects average cloudiness, so no further derating is needed for sizing.
- What panel tilt works best in Tokyo?
- At Tokyo's latitude (36°), a fixed tilt near 36° balances year-round yield. Winter-heavy loads favor latitude + 15°; summer-heavy, latitude − 15°.