How many solar panels for 1,250 kWh per month?
About 30 panels at 400 watts each, a 12 kW system, under the national-average 4.5 peak sun hours. This page is sized from a 1,250 kWh monthly bill, not from house square footage. Sun moves the count from 21 panels in the desert Southwest to 34 in the cloudiest states, and panel wattage trades count against roof area. Both tables below; your state in the picker.
Panel count by sun and wattage
Counts cover 1,250 kWh fully, rounded up to whole panels, with the 0.77 derate from rated watts to real output (methodology). Bold is the US-average column.
| Peak sun hours | 350W panels | 400W panels | 450W panels |
|---|---|---|---|
| 4.0 h | 39 | 34 | 30 |
| 4.5 h (US avg) | 34 | 30 | 27 |
| 5.0 h | 31 | 27 | 24 |
| 5.5 h | 28 | 25 | 22 |
| 6.0 h | 26 | 23 | 20 |
| 6.5 h | 24 | 21 | 19 |
Same bill, six real states
| State | Sun | Panels (400W) | System |
|---|---|---|---|
| Arizona | 6.5 h | 21 panels | 8.4 kW |
| Texas | 5.3 h | 26 panels | 10.4 kW |
| Florida | 5.2 h | 26 panels | 10.4 kW |
| Missouri | 4.6 h | 30 panels | 12 kW |
| New York | 3.9 h | 35 panels | 14 kW |
| Washington | 3.8 h | 36 panels | 14.4 kW |
What a 1,250 kWh household looks like
Twelve hundred fifty kWh says either a larger home, serious summer AC, or electric water heating on top of average use. It is worth knowing which before you size an array around it, because a heat-pump water heater can take roughly 200 kWh a month off the total, and the cheapest kilowatt-hour is still the one you stop using.
If the answer is electric water heating, the seasonal detail is worth having. Incoming water at the main swings 20°F or more between August and February, and the water heater pays for every one of those degrees: the same household draws noticeably more kilowatt-hours for the same showers in winter. That is exactly when peak sun hours bottom out. An annual average hides the mismatch entirely. It does not make the array wrong, and it does explain why the grid still does real work in January on a system sized to cover the year.
Questions people ask
How many solar panels do I need for 1,250 kWh per month?
About 30 400-watt panels (a 12 kW system) at the national-average 4.5 peak sun hours, after the 0.77 real-world output derate. Strong desert sun brings it down to 21; cloudy-state sun pushes it to 34. The tables on this page break it out by sun figure and panel wattage.
What system size covers 1,250 kWh a month?
Roughly 11.9 kW of DC capacity at average US sun; we round panels up, so the quoted 12 kW covers it with a little margin. In sunnier states the same bill takes proportionally less capacity, which is the whole reason the per-state figures matter.
Do I have to cover 100% of the bill?
No, and often you shouldn’t. Utilities with poor net-metering rates make the last 20% of offset the worst-value panels on the roof, and some cap system size at your historical usage anyway. Sizing to 70-90% of the bill is a normal, defensible design choice; covering every kWh is only automatic where net metering pays retail.
Why does my bill climb in winter if the heat is gas?
Usually the water heater. Incoming water at the main drops 20°F or more between August and February, and an electric water heater makes up every one of those degrees for the same showers. That is also the stretch of the year when peak sun hours are lowest, so a system sized on the annual average leans hardest on the grid in January. Expected, not a fault.