It's too expensive
Compared to what? Traditional energy systems will cost you a lot more than you might think. If you pay $100 per month in electricity, you'll spend over $32,000 in 20 years. Over that same period of a time, you'd spend almost $16,000 on natural gas just to heat your home's water.*
These are some numbers to use in comparing the economic cost of a solar energy system. A 3 kW solar PV array would cost around $25,000 to install and offset much of the electricity used in a typical home. A 2 panel solar water heating system would reduce a house's water heating load up to 80% and cost around $9,000. The upfront cost of the systems would be reduced by 30% from the federal tax credit and even further by state incentives. Since fuel costs are free in both of these solar systems, you would essentially fix your energy costs over the life of the systems (20 - 25 years)
Another way to look at cost is to gauge the environmental and health consequences of sticking with fossil fuels. Over half of our nation's electricity comes from coal. While the industry has gone to big efforts to refashion coal's dirty image as "clean", nothing in the coal supply chain is good for the environment, our health, local economies, or is sustainable in any way. Illinois is a coal state and we rank as the 6th worst US state in terms of CO2 emissions caused by our electricity industry. As the evidence mounts and our national focus changes, most of the externalized costs of coal will eventually be re-internalized and become reflected in the price that we pay for our energy. Solar externalizes nothing. You can feel good about your energy choices today when you chose to go solar.
* Calculations used 3% annual escalation on electricity and 5% on natural gas with $40/month spent to heat water.