Estimate system size, costs, savings, and environmental impact
Solar system size depends on your energy usage, sun hours in your area, and panel efficiency. The system should produce enough kWh annually to offset your electricity bill.
Formula
System Size (kW) = Annual kWh Usage ÷ (Sun Hours × 365 × 0.80)
For 10,000 kWh/year usage in an area with 5 peak sun hours: 10,000 ÷ (5 × 365 × 0.80) = 6.85 kW system needed.
Prices vary 20-30% between installers. Get at least 3 quotes and check reviews.
Panels last 25+ years. If your roof needs replacement in 10 years, do it first.
Review 12 months of usage before sizing. Your system should match actual consumption.
The 30% federal ITC lasts through 2032. State/local incentives may also apply.
Determine if solar makes financial sense for your situation.
Calculate the right system size for your needs.
Compare savings vs costs over the system lifetime.
Understand your carbon footprint reduction.
Average installed cost is $2.50-3.50 per watt. A 7 kW system costs $17,500-24,500 before incentives. The 30% federal tax credit significantly reduces net cost.
Typically 6-10 years depending on electricity rates and sun exposure. After payback, electricity is essentially free for the remaining 15-20+ year panel life.
25-30+ years with degradation of ~0.5% annually. After 25 years, panels still produce ~87% of original output.
Hours when sunlight intensity equals 1000W/m². Arizona gets 6-7; Seattle gets 3-4. This determines energy production, not daylight hours.
Yes, but at reduced capacity (10-25% of full sun). Panels still generate power from diffused light.
Batteries ($10,000-15,000+) store excess energy for night use or outages. Worthwhile if you have time-of-use rates or want backup power.
Utilities credit you for excess power sent to the grid. Policies vary—some pay retail rate, others wholesale. Check your utility's policy.