8.5 Is solar worth it if my bill is only $150/month?

Quick back-of-envelope math:

Suppose you're in California and your current bill is $150/month. Assume consumption rises 50% over 10 years and electricity rates double over 10 years (consistent with the last decade's actual trajectory). Total 10-year electricity spend if you do nothing: $36,000.

A solar system sized for that usage costs about $20,000. Under NEM 3.0, even with solar, you still draw some grid power and pay basic service fees, totaling about $40/month. So 10-year solar-era spend: $20,000 system + $4,800 utility = $24,800.

You invest $20K and save $11,000 over 10 years — averaging $1,100/year of savings.

You end up with a system you essentially got for free, plus an annual 6% yield, which beats almost every zero-risk passive investment available.

Extend the system's useful life to 25 years using the same usage and rate-growth trajectory, and the cumulative return exceeds 10×.