How much electricity does a solar panel produce?

Output depends on where the roof is, not only on the panel. Here's what one kW and one 400 W panel make in real cities.

A house with solar panels on the roof — Photo: Zendure Power Station / Unsplash

One kW of panels makes 1,318–1,788 kWh a year in the cities I cover, or 3.6–4.9 kWh a day on average (NREL PVWatts). A single 400 W panel makes about 527–715 kWh a year, 1.4–2.0 kWh a day.

Output by city

City	kWh a year per kW	kWh a day per kW	kWh a year per 400 W panel	kWh a day per panel	7 kW system, kWh a month
Phoenix, AZ	1,755	4.8	702	1.9	1,024
Tucson, AZ	1,788	4.9	715	2.0	1,043
San Antonio, TX	1,503	4.1	601	1.6	877
Austin, TX	1,483	4.1	593	1.6	865
San Diego, CA	1,716	4.7	686	1.9	1,001
Fresno, CA	1,654	4.5	662	1.8	965
Chandler, AZ	1,753	4.8	701	1.9	1,023
Scottsdale, AZ	1,745	4.8	698	1.9	1,018
Gilbert, AZ	1,750	4.8	700	1.9	1,021
Glendale, AZ	1,754	4.8	702	1.9	1,023
Tempe, AZ	1,752	4.8	701	1.9	1,022
Peoria, AZ	1,771	4.9	708	1.9	1,033
Surprise, AZ	1,785	4.9	714	2.0	1,041
San Jose, CA	1,624	4.4	650	1.8	947
Bakersfield, CA	1,684	4.6	674	1.8	982
Clovis, CA	1,659	4.5	664	1.8	968
Chula Vista, CA	1,728	4.7	691	1.9	1,008
Oceanside, CA	1,698	4.7	679	1.9	990
Carlsbad, CA	1,669	4.6	668	1.8	974
Toms River, NJ	1,376	3.8	550	1.5	803
New York, NY	1,353	3.7	541	1.5	789
Elizabeth, NJ	1,331	3.6	532	1.5	776
Yonkers, NY	1,318	3.6	527	1.4	769

NREL PVWatts v8 for the city center: fixed roof mount, south-facing, 20° tilt, 14% system losses. Daily figures are yearly averages.

Output by month

kWh per kW of panels, by month:

City	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Phoenix	118	123	151	170	178	173	158	155	147	142	124	117
Tucson	127	128	165	172	184	172	149	150	150	148	123	119
San Antonio	102	96	123	130	140	141	151	152	128	129	115	98
Austin	101	94	119	135	139	141	151	154	131	123	98	99
San Diego	116	114	143	159	156	168	170	170	152	137	118	113
Fresno	75	102	141	153	177	180	179	173	154	134	105	82
Chandler	117	122	155	169	180	170	157	157	147	144	123	112
Scottsdale	114	123	149	168	182	173	156	158	149	143	122	108
Gilbert	117	120	155	170	181	172	160	156	147	144	122	108
Glendale	115	127	153	171	180	170	160	154	150	143	122	109
Tempe	118	123	154	171	179	170	157	158	148	142	123	107
Peoria	121	117	154	171	181	172	161	161	150	142	124	116
Surprise	117	127	160	171	181	173	162	160	150	144	124	115
San Jose	80	87	141	148	169	173	185	177	150	135	95	85
Bakersfield	78	104	141	157	176	178	176	174	158	140	106	97
Clovis	83	99	144	155	175	174	179	173	157	134	105	82
Chula Vista	119	116	153	160	162	158	170	170	144	145	121	112
Oceanside	112	113	146	159	164	151	169	166	154	141	114	108
Carlsbad	115	117	150	157	150	156	166	165	143	129	112	110
Toms River	78	99	131	136	143	138	145	133	122	102	79	70
New York	82	100	115	116	143	134	149	127	122	107	88	70
Elizabeth	76	97	125	130	139	129	136	135	115	102	84	63
Yonkers	77	89	126	111	139	136	143	135	118	101	82	61

How to estimate your own system

Take the kWh a year per kW for your area from the table, or the calculator for any ZIP.
Multiply by your system size in kW.
Take off more if the roof is shaded or faces east or west.

A panel's watt rating is measured under standard test conditions; real output on a roof is lower, which is what the loss assumption above covers.

Check the production in your quote

Divide the quote's first-year production by its system size. If the result is well above the figure for your area, ask what orientation, shading and losses the installer assumed: how to check a solar quote.

Run your own numbers

Enter your ZIP and bill: I'll use NREL production for your ZIP to size a system.

Get quotes instead

Keep reading

How much solar panels save — Yearly and monthly savings by utility, and why they change from month to month.
How many solar panels you need — Size a system from your electric use and local sunshine, in four steps.
Solar on cloudy days, at night and in winter — How much output drops by season in each city, and what happens after dark or in an outage.

Updated 2026-09-26.