answer:Your terminology confuses me. An inverter, as I understand the term simply changes DC to AC so that the appliances you have that run on AC power can still be powered… by a DC battery, which in this case happened to be your UPS (which is essentially a large battery). So, given this understanding (and if your inverter was what I think it was), then it is quite understandable and necessary for your UPS to have been discharging, since it was providing the power you needed. I don’t know what generator you had used in the past, but a fuel-powered mechanical / electrical generator generally runs a motor to produce AC power (or DC, if it also includes its own inverter or you plug one in). If you can specify any models that you’ve used, perhaps someone who knows more about it than I do can answer more fully. Electricity is not my forte!