The average US home (10,500 kWh/year) needs 20-25 panels of 400W capacity. Calculate: Annual kWh / (Peak sun hours per day × 365) = System size in kW. Then divide by panel wattage for panel count. High-sun states like Arizona need fewer panels than cloudy states like Washington.

The typical US solar payback period is 6-12 years. With the federal 30% tax credit (IRA Investment Tax Credit), a $20,000 system costs $14,000 net. At $1,200/year in electricity savings, payback is about 11.7 years. Solar panels last 25-30 years, delivering 14-19 years of free electricity after payback.

The Inflation Reduction Act extended the federal solar Investment Tax Credit (ITC) at 30% through 2032. This means 30% of your total solar installation cost reduces your federal income tax bill dollar-for-dollar. Additional state credits (up to 25-30% in some states), rebates, and net metering further reduce effective costs.

Net metering allows you to sell excess solar electricity back to the grid at retail rates, dramatically improving ROI. A properly sized system with net metering can reduce electric bills by 80-100%. Net metering policies vary by state and utility — some states have moved to avoided-cost compensation, which is less favorable.

Yes. Germany, with less sunshine than most US states, is a world leader in solar adoption. Modern panels produce 10-25% of rated power on overcast days. Annual energy production depends more on total annual sunshine hours than individual sunny days. Seattle (about 2,100 sunshine hours/year) is still viable for solar, though less optimal than Phoenix (3,900 hours/year).