No, it is not possible nor practical.
1. Solar only gives you power during the day, if the sun is out. The more cloud cover you have the less solar production you get.
2. Snow cover on solar panels stops all solar production. Dust and dirt on your solar panels reduces production.
3. Wind energy from windmills/wind farms depends on weather patterns for good production.
4. Wind and solar energy production can not match the load for energy use.
5. At current costs and values, if you do NOT have a subsidy, wind and solar project have a 20 - 30 year simple payback. Life of those projects is often less than 20 - 30 years thus the life cycle cost is a negative, not a positive.
According to NASA, Dr. Hathaway, we could be headed into a new Dalton Minimum. that would mean global cooling not global warming. If you believe in AGW, then you might want to start lobbying for MORE CO2, not less.
Solar Panel Ratings approx 100 W per sq yd
2.5 Million Mega watts = 2.5 x 10^10 sq yd of solar panels
2.5 x 10^10 sq yd = 3,097,600 sq mi
Now you generally rate thee panels at 80% for production. Standard system design offset. So you need to divide that number by 0.8
Solar Panel area = 3,872,000 sq miles
To get a constant generation of 2,500,000 mega watts, you will need to make this area still alrger allowing for weather dust snow etc.
So you have an area approximately 2,000 miles by 2,000 miles. covered 100% by solar collection panels. This does not leave much room in the lower 48 for farms, forests, cities, homes, rivers, lakes...
My source? I design and install these systems.