How much power does a 400W solar panel produce per day?
A 400W solar panel produces about 1,548 Wh (1.55 kWh) a day at 4.5 peak sun hours after 14% losses — about 46.4 kWh a month and 565 kWh a year.
How to work it out
- 400 W × (1 − 14% losses) = 344 Wh per peak sun hour
- × 4.5 peak sun hours = 1,548 Wh a day (121 Ah at 12.8 V)
Four-hundred-watt panels are residential size — roughly the dimensions of a door — and are the usual choice for cabins, sheds and home systems. Where you live moves the answer by more than half.
Adjust for your project
More options: Losses · Battery V
- Per month (30 days)
- 46.4 kWh
- Per year
- 565 kWh
- Into a battery per day
- 121 Ah
- In one hour of full sun
- 344 Wh
- Peak charging current (MPPT)
- 31.3 A
Output at other peak sun hours
| Peak sun hours per day | Output per day | Per month (30 days) | Into a battery per day |
|---|---|---|---|
| 2 | 688 Wh | 20.6 kWh | 54 Ah |
| 3 | 1,032 Wh | 31 kWh | 81 Ah |
| 4 | 1,376 Wh | 41.3 kWh | 108 Ah |
| 5 | 1,720 Wh | 51.6 kWh | 134 Ah |
| 6 | 2,064 Wh | 61.9 kWh | 161 Ah |
| 7 | 2,408 Wh | 72.2 kWh | 188 Ah |
What a 400 W panel makes where you live
- Phoenix vs Seattle. PVWatts gives a tilted, south-facing 400 W panel about 715 kWh a year in Phoenix and about 428 kWh in Seattle — the same panel, two-thirds more energy in the desert.
- Per month. At this page’s 4.5 sun hours, about 46 kWh a month. The average US home used about 863 kWh a month in 2024 (EIA), so a whole-house system takes many panels — see how many solar panels for 1000 kWh per month.
- Off-grid on 12 V? Its higher voltage almost always means an MPPT controller; at 12.8 V the charge current can reach about 31 A.
- Big and heavy. These panels need a proper mount and two people to lift; check your roof or rack before you buy.
The current a 400 W panel sends into a 12 V battery is worked out on 400 watts to amps at 12V, and the controller on what size charge controller for a 400 watt solar panel. Smaller panels: how much power a 200W solar panel produces per day.
Different size? Use the full Solar Panel Output Calculator.
What you’ll need
- 400 W residential-size solar panelPremium price
Fewer, larger panels for a cabin, shed or ground mount. Their higher voltage usually means an MPPT controller.
See options on Amazon (opens in a new tab) - MPPT solar charge controllerMid-range price
Converts a higher panel voltage into charging current, so you can wire panels in series and lose less in the cables. Size it on output amps and maximum PV voltage.
See options on Amazon (opens in a new tab) - Adjustable tilt mount bracketsBudget price
Lets you change a ground- or roof-mounted panel’s angle with the seasons instead of leaving it flat.
See options on Amazon (opens in a new tab)
As an Amazon Associate we earn from qualifying purchases. Links to products are affiliate links — they cost you nothing extra and help keep these calculators free.
Frequently asked questions
How much power does a 400W solar panel produce in Phoenix per day?
About 2,260 Wh a day at 6.57 peak sun hours.
How much power do ten 400W solar panels produce per month?
About 464.4 kWh a month at 4.5 peak sun hours (4 kW of panels).
Other common sizes
- How much power a 100W solar panel produces per day — 387 Wh a day at 4.5 sun hours
- How much power a 200W solar panel produces per day — 774 Wh a day at 4.5 sun hours
Sources
- National Laboratory of the Rockies (formerly NREL) — PVWatts® Calculator (opens in a new tab) — Look up the solar resource (peak sun hours) and yearly output for your own address; default system losses 14%.
- NLR (formerly NREL) — PVWatts® v8 API, NSRDB PSM V3 TMY data (opens in a new tab) — City figures on this site: fixed open-rack array facing due south, tilted at the site’s latitude, 14% system losses, queried October 2026.
- Victron Energy — Which solar charge controller: PWM or MPPT? (2020) (opens in a new tab) — MPPT output current = panel watts ÷ battery voltage (100 W ÷ 13 V = 7.7 A); a PWM controller pulls the panel down to battery voltage (81 W from a 100 W panel at 25 °C, about the same as MPPT at 75 °C); temperature-coefficient method; example panel Voc 21.6 V, −0.35 %/°C.