What Size Solar System Do I Need for 2 kWh per Day?
Two kilowatt-hours sits just under Battle Born's own 2,400 Wh example. The interesting part is what the 20% margin does to that gap.
Full breakdown: what size solar system.
If 2 kWh is a cabin weekend rather than a single number, use off-grid cabin solar and how many solar panels for a cabin.
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Array watts at three sun figures
| Sun assumption | Array watts | Plus 20% | Plus 30% | Source |
|---|---|---|---|---|
| 4 peak sun hours | 500 W | 600 W | 650 W | Battle Born |
| 5 peak sun hours | 400 W | 480 W | 520 W | Battle Born |
| Phoenix December, 4.75 | 421.1 W | 505.3 W | 547.4 W | PVWatts; margin Battle Born |
The 2,000 Wh rows use Battle Born's 4 to 5 hour baseline. Phoenix December stays at 4.75 so a sunny winter is not mistaken for the annual 6.54 kWh/m²/day.
How to size it
Battle Born's published example is 2,400 Wh/day ÷ 4 peak sun hours = 600 W, and they do that division before mentioning the extra 20 to 30 percent. This page's load is 2,000 Wh, which is 400 Wh under their example. Watch what the margin does:
- 2,000 ÷ 4 = 500 W.
- 2,000 W-hours worth of margin: 500 × 1.20 = 600 W, and 500 × 1.30 = 650 W. The 20% case equals the 600 W in their larger example.
- At 5 peak sun hours: 2,000 ÷ 5 = 400 W, then 480–520 W.
- Phoenix December is 4.75, not the annual 6.54. 2,000 ÷ 4.75 = 421.1 W, then 505.3 W and 547.4 W.
- Illustrative 400 W panels, rounded up: the 650 W margin needs 2 panels (650 ÷ 400 = 1.625). The bare 5-hour case is 400 W, which is one 400 W module before the margin and still 2 once 30% is added.
Their lithium note is separate from this load math: about 200 W of solar per 100 Ah of LiFePO4, and 200 Ah of lithium (two 100 Ah batteries) is where they recommend 400 to 600 W. A 2 kWh daily load at 12 V is 166.7 Ah for one day, near that 200 Ah example, and the load-based array with margin (600–650 W) sits at the top of their 400–600 W battery guideline rather than in the middle of it. Use the guideline when you are sizing panels to a battery you already own; use the watt-hour division when the load is what you know.
Battery amp-hours from the same watt-hours
| Autonomy | Watt-hours to store | Amp-hours at 12 V | Source |
|---|---|---|---|
| One day | 2,000 Wh | 166.7 Ah | Battle Born battery article (Wh ÷ 12 V) |
| Two days | double | 333.3 Ah | Battle Born: two days off-grid doubles capacity |
Apply Wh ÷ 12 V to 2,000 Wh and you get 166.7 Ah for one day. Two days doubles it. Twelve volts is the example voltage, taken from 2,400 Wh ÷ 12 V = 200 Ah. Hand that amp-hour figure to the battery bank sizer if the bank is the next decision.
Replace 2,000 Wh with a measured day, then repeat the division in the solar size calculator or at your coordinates in PVWatts.
FAQ
How does 2 kWh compare with Battle Born's 2,400 Wh example?
Their example is 2,400 Wh ÷ 4 = 600 W with no margin applied in that line. This page's 2,000 ÷ 4 = 500 W, and 500 × 1.20 = 600 W, the same 600 W their example gets from the larger load.
What if the site gets 5 peak sun hours?
2,000 ÷ 5 = 400 W. The 20 to 30 percent band on that is 480–520 W.
What battery goes with 2 kWh a day?
Using the 12 V in Battle Born's battery example, 2,000 ÷ 12 = 166.7 Ah for one day. Two days doubles that to 333.3 Ah.
How many illustrative 400 W panels is 650 W?
650 ÷ 400 = 1.625, which rounds up to 2 panels. Four hundred watts is only the divisor used to force a whole-module count.
Related questions
- What size solar system for 1 kWh per day
- What size solar system for 5 kWh per day
- What size solar system for a refrigerator
All of these questions are listed on the topic map.
Sources
- Battle Born Batteries, How to Size Solar Panels for a Deep Cycle Battery System — accessed Oct 2, 2026.
- Battle Born Batteries, How to Size a Deep Cycle Battery Bank — accessed Oct 2, 2026.
- NREL/NLR PVWatts Version 8 API documentation — accessed Oct 2, 2026.
- PVWatts calculator — accessed Oct 2, 2026.