I am currently working on a calculation to see whether it is economically feasible for a household to invest in an energy retrofit. I obtain a total profit of around $13\%$ over the lifetime of the investement ($25$ years), which translates to an average annual rate of return of $0.52\%$. This investment is mostly risk-free, to the extent that heating fuel prices remain stable.
What are example of benchmarks that I could use to evaluate this return rate? That is, to make a case for/against the household investing in the energy retrofit?