What Size Solar System Do I Need for 1 kWh per Day?

One kilowatt-hour a day is a small off-grid load. The array is that energy divided by peak sun hours, then padded 20–30% if you have the roof or ground space.

Full breakdown: what size solar system.

Cabin context, if this kilowatt-hour is only part of a cabin day: off-grid cabin solar and how many solar panels for a cabin.

Array watts at three sun figures

For this 1,000 Wh input, 4 to 5 peak sun hours are the baseline. December in the Phoenix run is 4.75, the low month, while the annual plane-of-array figure is 6.54 kWh/m²/day. Use 4.75 for the winter check, not 6.54.

How to size it

Battle Born's panel article divides daily watt-hours by peak sun hours. Their worked line is 2,400 Wh ÷ 4 peak sun hours = 600 W. The same division on this page's 1,000 Wh input is smaller, and it still uses their 4 to 5 hour baseline.

1. Start from the question's load: 1,000 Wh per day. That is the input, not a measured appliance.
2. At 4 peak sun hours: 1,000 ÷ 4 = 250 W. Add 20%: 250 × 1.20 = 300 W. Add 30%: 250 × 1.30 = 325 W.
3. At 5 peak sun hours: 1,000 ÷ 5 = 200 W, then 240 W and 260 W.
4. Sunny-site winter check: Phoenix December plane-of-array sun is 4.75 (the low month; the same run's annual plane-of-array is 6.54). 1,000 ÷ 4.75 = 210.5 W, then 252.6 W and 273.7 W.
5. Panel count, using 400 W only as an illustrative divisor: 325 ÷ 400 rounds up to 1 panel. The bare 250 W case is also 1 panel. This is a count, not a product rating.

Nameplate watts are not the daily total. Champion lists an LED bulb at 8–15 W and a router at 10–20 W, and Honda lists a laptop at 200–250 W. Hours of use are yours to measure; this page does not invent them. A refrigerator example of 500 Wh is half of this 1,000 Wh day, and a 60 W CPAP held for an example 8-hour night is 480 Wh, just under half.

Battery amp-hours from the same watt-hours

The 12 V in the 2,400 Wh ÷ 12 V = 200 Ah example is only the voltage used to turn 1,000 Wh into 83.3 Ah. It is not a rule that a small load must be a 12 V bank. Continue that amp-hour result on the battery bank sizer.

Put your real load list into the solar size calculator, and replace the Phoenix check with your own address in PVWatts.

FAQ

Is 250 W enough for 1 kWh a day?

At 4 peak sun hours, 1,000 ÷ 4 = 250 W before losses. Battle Born says to add 20 to 30 percent when space allows, which is 300–325 W. The 250 W figure is only the bare division.

Why show a Phoenix December check?

Battle Born calls 4 to 5 peak sun hours a reasonable baseline in many areas. The Phoenix PVWatts run's lowest month is December at 4.75, against an annual plane-of-array of 6.54 kWh/m²/day. That 4.75 is a sunny-site winter check, not a national winter.

How many amp-hours store 1 kWh?

Battle Born divides watt-hours by system voltage. Their example is 2,400 Wh ÷ 12 V = 200 Ah. On 1,000 Wh that is 83.3 Ah for one day. Two days off-grid doubles it to 166.7 Ah.

Does one 400 W panel cover the margin?

325 W ÷ 400 W rounds up to 1 panel. The 400 W step is an illustrative divisor so the count is a whole number of modules, not a claim about a specific panel.

Related questions

• What size solar system for 2 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.
• Champion Power Equipment, Generator Wattage Chart — accessed Oct 2, 2026.
• Honda, What wattage generator do I need? — accessed Oct 2, 2026.