Hello,
My heat pump is having an issue where if the power flickers or fluctuates during a storm, the water heater stops making hot water at the right settings. I need a 120v power supply that will maintain and stabilize the incoming power so that this stops happening. What product do I need?
It depends on how much current you need and for how long.
Depending on those values the price can range from less than $100 to more than $10,000. Then there may be on going maintenance costs.
I would contact a couple of companies that install and maintain systems like yours. It is very likely they can offer a fix that is more cost effective and have the lowest future maintenance costs.