The thing about investing in your own energy or food production is that you not only reduce your monthly costs but also end up owning productive assets.
John Robb sees this as financially bootstraping communities seeking to bolster their resilience (via globalguerillas).
According to Robb, owning a windmill, solar array or garden is superior to owning a retirement account...especially in the likely inflationary economy of the near future.
Robb expects that the monthly savings will far exceed the monthly returns on your 401k/IRA accounts. Moreover, notes Robb, "as returns accumulate, it makes possible new investments in productive systems with additional cash flow opportunity."
Robb shows how solar systems can generate 4% returns, then suggests applying the same methodology to lawn gardening or farm 'shares/subscriptions'. "The same results are likely to apply", says Robb. "Food expenses are turned into savings. Ownership of local food production is the result."
Using NREL's "IMBY" tool, I found a combination of wind/solar costing (net) under $6k could generate savings of $600-$1,000 annually (as KIUC rates range from $0.27 - $0.50...for an APR of 10%-18%. Try beat that rate with your IRA...