How payback is calculated
Net upfront cost adds purchase, delivery, installation and disposal, then subtracts the discount without allowing a negative result. Annual net saving is the old annual energy cost minus the new annual energy cost and any additional maintenance. Positive net saving is divided into upfront cost.
If annual net saving is zero or negative, the tool does not divide by zero and states that there is no financial payback at the entered figures. Five-year and ownership-period net positions remain visible.