How Many Solar Panels for 800 kWh per Month?
To cover 800 kWh per month you need about 7.3 kW of solar, or 19 panels of 400 W, assuming 4.5 peak sun hours a day. Depending on where you live that ranges from 14 panels (Southwest) to 24 panels (Northeast). The array needs roughly 399 sq ft of roof.
Solar panels for 800 kWh by region
| Region | Sun hours | System size | 400 W panels | Roof space |
|---|---|---|---|---|
| Northeast / Pacific Northwest | 3.5 | 9.39 kW | 24 | 504 sq ft |
| Midwest / Mid-Atlantic | 4.5 | 7.31 kW | 19 | 399 sq ft |
| Southeast / Texas | 5 | 6.58 kW | 17 | 357 sq ft |
| Southwest | 6 | 5.48 kW | 14 | 294 sq ft |
Based on 100% offset, 400 W panels and about 21 sq ft per panel. Peak sun hours are regional averages.
Cost of a 7.3 kW system
| Region | System size | At $2.50/W | At $3.00/W | At $3.50/W |
|---|---|---|---|---|
| Northeast / Pacific Northwest | 9.39 kW | $23,483 | $28,180 | $32,877 |
| Midwest / Mid-Atlantic | 7.31 kW | $18,265 | $21,918 | $25,571 |
| Southeast / Texas | 6.58 kW | $16,438 | $19,726 | $23,014 |
| Southwest | 5.48 kW | $13,699 | $16,438 | $19,178 |
Installed cost before any rebates. Cost is system watts × price per watt. The federal 25D credit ended for systems installed after December 31, 2025.
How it is calculated (4.5 sun hours)
800 kWh × 12 = 9,600 kWh per year (26.3 kWh per day)
9,600 ÷ (4.5 × 365 × 0.8) = 7.31 kW
7,306 W ÷ 400 W = 18.26 → 19 panels
19 × 21 sq ft = 399 sq ft of roof
Tips at 800 kWh per month
- Typical home range – This is close to an average US household. A 19-panel array (about 399 sq ft) usually fits on one or two roof planes.
- Panel wattage choice – Higher-wattage panels cut the count: at 450 W the same system needs about 17 panels instead of 19, which helps on smaller roofs.
- Batteries – Panels alone do not give backup power in an outage. A battery is sized separately and mainly pays off with time-of-use rates or poor net metering.
Frequently asked questions
How many solar panels do I need for 800 kWh per month?
About 19 panels of 400 W (7.31 kW) in a region with 4.5 peak sun hours. That ranges from 14 panels in the Southwest to 24 in the Northeast and Pacific Northwest.
How big a solar system do I need for 800 kWh a month?
800 kWh a month is 9,600 kWh a year. Divided by 4.5 sun hours × 365 days × 0.8 system efficiency, that gives a 7.31 kW system. It is 5.48 kW with 6.0 sun hours and 9.39 kW with 3.5.
How much does solar cost for 800 kWh per month?
At 4.5 sun hours the system costs about $18,265 to $25,571 installed ($2.50–$3.50 per watt), or $21,918 at $3.00. The federal 25D credit ended for systems installed after December 31, 2025, so check state and utility rebates separately.