How Many kWh Does A Solar Panel Produce Per Day? (Calculator + 2026 Tables)

I built a 6 kW array on my own house in 2024 and have logged production every day since. The number that comes off the inverter every day is exactly what the formula below predicts — within about 5%. This article skips the theory (we covered that in how to calculate solar panel output) and gives you the lookup tables and worked numbers for every common solar panel and system size in the U.S.

The complete formula in one line:

kWh per day = (panel watts ÷ 1,000) × peak sun hours × 0.83

The 0.83 is the PVWatts v8 default derate factor — the same number every U.S. solar installer uses. It accounts for inverter losses, soiling, shading, mismatch, wiring, connectors, light-induced degradation, and downtime. Part of this loss comes from temperature — panels on a hot roof produce less than their lab rating, which is why the STC vs NOCT (NMOT) comparison matters when you read datasheets. For the full breakdown of where every percentage point goes, see the formula article. For the exact peak sun hours at your location, use the peak sun hours calculator.

Solar Panel Daily kWh Calculator

Input your panel wattage and your peak sun hours; the calculator gives you daily, monthly, and annual production.

Don't know your peak sun hours? Use our peak sun hours calculator → It pulls from NREL PVWatts v8 and the National Solar Radiation Database, the same dataset every U.S. solar installer uses.

Daily kWh Output By Panel Size (4–7 Peak Sun Hours)

This is the chart you came here for. All numbers calculated with the PVWatts v8 default derate of 0.83, which corresponds to NREL's default 14% total system loss assumption. Bold rows are the most common residential and commercial panel sizes in 2026.

Quick examples you can take straight from this table:

• A 400 W panel at the U.S. average (5 PSH) produces about 1.66 kWh per day — enough to fully run a standard 1.3 kWh/day refrigerator with a quarter of a kWh left over.
• A 300 W panel in Seattle (4 PSH) produces about 1.00 kWh per day — a typical full-size LED TV running 14 hours, or your laptop running for two solid work days.
• A 500 W panel in Phoenix (6.5 PSH) produces about 2.71 kWh per day — enough to charge an electric bike daily and still have margin to power a workshop.

Daily kWh Output By System Size (4–7 Peak Sun Hours)

For systems instead of single panels. Same derate (0.83). Bold rows are the most common residential install sizes.

Annual kWh is daily × 365. Monthly is daily × 30 (close enough, give or take a day). The actual monthly variation is much bigger than ±1 day worth — see the seasonal section below.

What Can Your Daily kWh Actually Run?

Numbers like "25 kWh/day" don't mean much without something to compare them against. Here's what common appliances actually use, so you can map daily solar production to lifestyle.

So a typical 6 kW system at 5 PSH (24.9 kWh/day) covers most of an average U.S. household's daily use — on average. Summer days are higher and winter days lower. A 5 kW system covers everything except heavy AC use; a 10 kW system covers everything plus an EV.

EIA data: average U.S. household uses 10,791 kWh/year (2024 RECS, residential survey). That's 29.6 kWh/day averaged across the year.

Daily kWh Output By US City (Real PSH Numbers)

Generic 4/5/6/7 PSH tables are useful but don't tell you what your number is. Here's daily output for the four most-common configurations across 12 U.S. cities, using the actual NREL annual peak sun hours for each city.

All values in kWh per day. The same panel produces 2× more energy in Phoenix than in Anchorage for free. This is the single biggest variable in residential solar economics — your location determines about 60% of your annual generation, the rest comes from system design and equipment.

Seasonal Variation: Daily Output Isn't Constant

The numbers above are annual averages. In reality, daily production varies a lot between summer and winter — the further from the equator you are, the bigger the swing. Same 6 kW system, three very different cities:

This is why net metering and battery storage matter. In Boston, your 6 kW system makes 30 kWh/day in June but only 12 kWh/day in December. Net metering lets you "bank" the summer surplus against winter usage. A battery does the same on a daily scale (charge during the day, discharge after sunset).

Two things to take away from this table:

1. High latitudes have brutal winters for solar — Anchorage's December production is only 6% of June. Even Boston is at 38%. And yes, solar panels still work on cloudy days, just at reduced output.
2. Sunbelt cities are much more consistent — Phoenix never drops below 58% of its summer peak.

For exact monthly numbers at your specific location, use the peak sun hours calculator. It returns the full 12-month array directly from NREL PVWatts.

From Daily To Annual: The Conversion

Once you know your daily output, the rest is multiplication.

Worked example: a 6 kW system in Boston at 4.70 PSH produces 23.4 kWh/day:

• Monthly avg: 23.4 × 30 = 702 kWh
• Annual: 23.4 × 365 = 8,541 kWh
• 25-year lifetime: ≈ 200,000 kWh (with ~10% degradation by year 25)

At Boston's average residential rate of $0.32/kWh (Eversource, 2026), that 25-year lifetime production is worth roughly $64,000 of avoided electric bills — before any tax credits or rebates.

Common Mistakes When Estimating Daily kWh

After helping people on Reddit and forums for two years, these are the four mistakes I see most often:

1. Using the wrong peak sun hours

The most common error. People look up "average daylight hours" instead of peak sun hours and end up with a number 2–3× too high. Daylight is not PSH. See average peak sun hours by state for the correct numbers. A 14-hour summer day in Phoenix is roughly 7–8 PSH, not 14.

2. Forgetting the derate

The raw kW × PSH number is your DC nameplate output. The number that actually shows up at your meter is 17% lower because of inverter losses, soiling, mismatch, wiring, and so on. The derate factor (0.83 for PVWatts default, 0.77 for conservative) is not optional.

3. Confusing watts and kilowatts

A 400W panel is 0.4 kW, not 400 kW. The formula uses kW. The most common version of this mistake produces a number 1,000× too big.

4. Treating annual averages as daily realities

Boston's 4.70 PSH annual average doesn't mean Boston gets 4.70 PSH every day. December gets ~2.3, June gets ~6.1. If you're sizing a battery or planning winter usage, always use the worst-month figure, not the annual average.

Bottom Line

For the lazy answer:

kWh per day = (panel watts ÷ 1,000) × peak sun hours × 0.83

For the worked answer: use the table that matches your panel size and your peak sun hours. For your exact peak sun hours, use the calculator. For the why behind the 0.83, see the formula article. For your system size, see the system table above.

Average U.S. household uses 28.8 kWh/day. The system size that will fully cover an average household at the U.S. average PSH (5.0) is 6.95 kW — call it 7 kW. That's about 18 modern 400W panels, occupying roughly 350 sq ft of unobstructed south-facing roof. Optimizing your panel tilt angle can squeeze another 3–5% out of the same array.

Keep Reading

• Peak Sun Hours Calculator — Find PSH At Your Location — the input you need for any of these tables
• How To Calculate Solar Panel Output — the formula breakdown and derate methodology
• Standard Solar Panel Sizes And Wattages (100W–600W) — for picking your panel watts
• Solar Panel Watts Per Square Foot — area-based version of this question
• Average Peak Sun Hours By State
• How Much Power A 5 kW Solar System Produces
• How Much Power A 10 kW Solar System Produces
• How Many Panels In A 1kW, 5kW, 10kW Solar System
• Rooftop Solar Calculator — How Many Panels Fit On Your Roof