SolarSizer

What Size Solar System Do I Need for 10 kWh per Day?

Ten kilowatt-hours is well past a weekend cabin and still well under a U.S. household day. The array math is the same division, at a size where the margin is a whole extra kilowatt.

Full breakdown: what size solar system.

When production falls short of this daily rate, the backup discussion is solar vs generator for off-grid. This page only sizes the array for the sun hours below.

Quick answer: Ten thousand watt-hours at 4 peak sun hours is 2,500 W, or 3,000–3,250 W with the 20–30% margin. At 5 hours the margin is 2,400–2,600 W. A Phoenix December check at 4.75 starts at 2,105.3 W. Use PVWatts at your address or the solar size calculator before treating these as a bill of materials.
Affiliate

Affiliate disclosure: as an Amazon Associate, we earn from qualifying purchases — at no cost to you.

Shop a 3000 watt solar panel kit with battery on Amazon

Array watts at three sun figures

Sun assumptionArray wattsPlus 20%Plus 30%Source
4 peak sun hours2,500 W3,000 W3,250 WBattle Born
5 peak sun hours2,000 W2,400 W2,600 WBattle Born
Phoenix December, 4.752,105.3 W2,526.3 W2,736.8 WPVWatts; margin Battle Born

On a 10,000 Wh day the 4 to 5 hour baseline and a Phoenix December of 4.75 are the three divisors. Annual plane-of-array sun in that run is 6.54 kWh/m²/day, which is not the winter check.

How to size it

Double a 5 kWh day and the watts double, because the Battle Born step is a division, not a tier chart. The margin is where the extra kilowatt appears: 30% of 2,500 W is 750 W, and 2,500 + 750 = 3,250 W.

  1. 10,000 ÷ 4 = 2,500 W. Plus 20% = 3,000 W. Plus 30% = 3,250 W.
  2. 10,000 ÷ 5 = 2,000 W, then 2,400 W and 2,600 W.
  3. 10,000 ÷ 4.75 = 2,105.3 W, then 2,526.3–2,736.8 W. That 4.75 is December in Phoenix. The annual 6.54 kWh/m²/day is a different number and would shrink this array if you used it by mistake.
  4. Illustrative 400 W count at the high 4-hour case: 3,250 ÷ 400 = 8.125, rounding up to 9 panels. The 5-hour 30% case (2,600 W) rounds up to 7 panels.

EIA puts average residential use at about 899 kWh per month. Dividing that by 30 days is 29.97 kWh per day, so 10 kWh is about a third of the average household day (10 ÷ 29.97 = 0.33). It is not the average-home array. The average-home page uses the annual 10,791 kWh and a yearly yield; this page uses one day's watt-hours and peak sun hours.

These watts are what the array has to produce across the peak sun hours you assumed. They say nothing about a week of cloud. That limit is why the generator comparison is linked above.

Battery amp-hours from the same watt-hours

AutonomyWatt-hours to storeAmp-hours at 12 VSource
One day10,000 Wh833.3 AhBattle Born battery article (Wh ÷ 12 V)
Two daysdouble1,666.7 AhBattle Born: two days off-grid doubles capacity

10,000 Wh ÷ 12 V = 833.3 Ah using the voltage in the 2,400 Wh ÷ 12 V = 200 Ah example. Two days is 1,666.7 Ah. Take the amp-hours to the battery bank sizer rather than treating 12 V as mandatory.

Log the real 10 kWh — or whatever your meter shows — in the solar size calculator, and run the site in PVWatts.

Affiliate

Shop an MPPT solar charge controller on Amazon Shop a 12V 100Ah LiFePO4 battery on Amazon

FAQ

Is 10 kWh a day an average home?

No. EIA reports about 899 kWh per month. Divided by 30 days that is 29.97 kWh per day. Ten kilowatt-hours is about a third of that (10 ÷ 29.97 = 0.33).

What array replaces 10 kWh at 4 peak sun hours?

10,000 ÷ 4 = 2,500 W. With 20 to 30 percent more, plan 3,000–3,250 W.

What is the Phoenix December array?

December in the Phoenix PVWatts run is 4.75. 10,000 ÷ 4.75 = 2,105.3 W before the margin, and 2,526.3–2,736.8 W after it.

Why link a generator page from an array calculation?

The 3,000–3,250 W result is production during the peak sun hours in the denominator. It is not a store of energy for dark days. Backup is a separate decision; the array math stops once the division is done.

Related questions

All of these questions are listed on the topic map.

Sources