How many solar panels for 800 kWh per month in California?15 panels
Turn your electricity use into system capacity using a cached PVWatts production estimate.
Your starting point
15 panels
6.00 kW DC · 400 W panels
Planning range
13–17 panels
A screening estimate under the assumptions below. The range is a shopping guide, not a guarantee.
Planning estimate. A licensed contractor must confirm the final size, installation and local code requirements. Electrical work needs a licensed electrician.
Adjust your home
The calculation, step by step.
Annual target kWh / cached PVWatts kWh per kW-year, divided by panel kW, rounded upward.
| Input or step | Calculated amount |
|---|---|
| Monthly consumption | 800 kWh |
| Annual offset target | 9,600 kWh |
| PVWatts production factor | 1,705 kWh/kW/year |
| Unrounded system | 5.63 kW DC |
| Rounded panel system | 6.00 kW DC |
| Panel footprint | 315 sq ft |
| Usable roof | 600 sq ft |
What moves this number?
Electricity use
Use 12 months of bills. Floor area is only an optional consumption proxy.
Roof conditions
This snapshot assumes south-facing 30-degree roof mounting, 14% losses, and no property-specific shade model.
Panel wattage
Higher-wattage panels reduce the panel count, not the required energy.
Your location and assumptions.
Solar uses a representative-city weather snapshot for California. It is not a statewide average or a property-specific shade assessment.
- Representative city: Los Angeles; not a statewide average.
- PVWatts v8; 1 kW DC, standard modules, roof mounted, 30-degree tilt, 180-degree azimuth, 14% system losses.
- Snapshot retrieved 2026-10-01. Weather: NSRDB PSM V3 GOES tmy-2020 3.2.0.
- Panel footprint 21 sq ft each is a user assumption; code setbacks and access paths need extra roof space.
- +/-15% production band is a screening sensitivity, not PVWatts statistical uncertainty.
What might it cost to run?
Annual energy matching estimates capacity, not savings. A savings estimate needs your import/export tariff, fixed charges, installation quote and consumption timing.
Before you choose equipment.
Annual generation matching does not guarantee bill elimination, off-grid operation or outage power. Roof shade, orientation, utility rules and seasonal weather can change production.
Bring this calculation to your installer. They will check the measured load, manufacturer performance, distribution or connections, installation conditions and local requirements.
A few more sizing questions.
How many panels for 800 kWh per month?
The default screen gives 15 panels, with a planning range of 13–17 panels. Change the inputs above to reflect your actual home. At 400 W each, the rounded system is 6.00 kW DC.
Does square footage determine solar size?
Electricity use is the stronger input. Area mode scales the EIA California household average relative to a 2,000 sq ft reference home; this is an illustrative proxy, not measured usage.
Is this production for my exact roof?
No. The cached PVWatts snapshot uses Los Angeles weather, south-facing 30° roof mounting and 14% losses. Shading, orientation and actual weather can change the result.
Will these panels eliminate my bill or power an outage?
Matching annual generation does not guarantee either. Export rates, fixed charges and timing affect bills. Outage power requires suitable battery and islanding equipment.
Will the panels fit?
Their assumed footprint is 315 sq ft compared with 600 sq ft of usable roof. That passes this simple footprint check. Setbacks, access paths, structure and layout need a site assessment.
Is this a final equipment size?
No. A licensed contractor must measure your building or actual loads, check manufacturer performance and local code, and confirm the final selection.