How Many Solar Panels for 700 kWh per Month?
To cover 700 kWh per month you need about 6.4 kW of solar, or 16 panels of 400 W, assuming 4.5 peak sun hours a day. Depending on where you live that ranges from 12 panels (Southwest) to 21 panels (Northeast). The array needs roughly 336 sq ft of roof.
Solar panels for 700 kWh by region
| Region | Sun hours | System size | 400 W panels | Roof space |
|---|---|---|---|---|
| Northeast / Pacific Northwest | 3.5 | 8.22 kW | 21 | 441 sq ft |
| Midwest / Mid-Atlantic | 4.5 | 6.39 kW | 16 | 336 sq ft |
| Southeast / Texas | 5 | 5.75 kW | 15 | 315 sq ft |
| Southwest | 6 | 4.79 kW | 12 | 252 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 6.4 kW system
| Region | System size | At $2.50/W | At $3.00/W | At $3.50/W |
|---|---|---|---|---|
| Northeast / Pacific Northwest | 8.22 kW | $20,548 | $24,658 | $28,767 |
| Midwest / Mid-Atlantic | 6.39 kW | $15,982 | $19,178 | $22,374 |
| Southeast / Texas | 5.75 kW | $14,384 | $17,260 | $20,137 |
| Southwest | 4.79 kW | $11,986 | $14,384 | $16,781 |
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)
700 kWh × 12 = 8,400 kWh per year (23 kWh per day)
8,400 ÷ (4.5 × 365 × 0.8) = 6.39 kW
6,393 W ÷ 400 W = 15.98 → 16 panels
16 × 21 sq ft = 336 sq ft of roof
Tips at 700 kWh per month
- Efficiency first – At 700 kWh a month, an LED, heat-pump or insulation upgrade can shave the system by a few panels – each panel avoided saves roughly $1,000 installed at $2.50–$3.50 per watt.
- Small roofs work – 16 panels need only about 336 sq ft, so a single south- or west-facing roof plane is usually enough.
- 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 700 kWh per month?
About 16 panels of 400 W (6.39 kW) in a region with 4.5 peak sun hours. That ranges from 12 panels in the Southwest to 21 in the Northeast and Pacific Northwest.
How big a solar system do I need for 700 kWh a month?
700 kWh a month is 8,400 kWh a year. Divided by 4.5 sun hours × 365 days × 0.8 system efficiency, that gives a 6.39 kW system. It is 4.79 kW with 6.0 sun hours and 8.22 kW with 3.5.
How much does solar cost for 700 kWh per month?
At 4.5 sun hours the system costs about $15,982 to $22,374 installed ($2.50–$3.50 per watt), or $19,178 at $3.00. The federal 25D credit ended for systems installed after December 31, 2025, so check state and utility rebates separately.