Calculate exactly how many solar panels you need to offset your electricity bill based on your location and roof conditions.
The right solar system size depends on your energy usage, location, and roof conditions. Here's what affects your sizing:
| System Size | Panels | Best For | Cost (after credit) |
|---|---|---|---|
| 4 kW | 10 panels | Small home, $80-100/mo bill | $7,700 |
| 6 kW | 15 panels | Average home, $120-150/mo bill | $11,500 |
| 8 kW | 20 panels | Larger home, $180-220/mo bill | $15,400 |
| 10 kW | 25 panels | Large home or EV owner | $19,250 |
| 12+ kW | 30+ panels | High usage, multiple EVs, pool | $23,000+ |
Not necessarily. Many homeowners aim for 80-100% offset. Reasons to size smaller: if your utility has unfavorable net metering (you don't get full credit for excess), if you have roof space limitations, or if you plan to reduce usage through efficiency upgrades. Reasons to size larger: if you plan to add an EV, heat pump, or pool.
Each 400W panel needs about 18 square feet. A typical residential roof has 1,000-2,000 usable square feet after accounting for setbacks, vents, skylights, and optimal orientation. That's room for 15-30 panels (6-12 kW). Installers will assess your specific roof during a site visit.
Options include: higher-efficiency panels (up to 22% vs standard 20%), ground-mounted systems if you have yard space, carport or pergola installations, or community solar programs where you buy into a shared solar farm. Ground-mounted systems add $0.10-0.20/watt but allow optimal positioning.
Batteries (like Tesla Powerwall) add $10,000-15,000 but provide backup power and can increase savings if you have time-of-use rates. If planning batteries, size your solar system 10-20% larger to charge them. Batteries qualify for the 30% tax credit when installed with solar.
See detailed payback periods, 25-year savings, and compare solar to other home upgrades.