Why is there only hot water when my AC is on?!

If you have an electric hot water heater, it seems its on the same circuit as the AC is on, which by code is a NO NO! The AC unit has to be on its own circuit as well as the hot water heater. If this is so, you would need an electrician to place them on their own circuit. This involves working inside the circuit box and I don't advise any one to try to do it themselves without experience.

Long shot...Do you have a 'water source' heat pump? If so, all the cooler water could be diverting to the heat pump prior to the other pipes...

Judy Roberts may not be such a long shot, if she does have a heat pump she needs to prepare for high heating bills also, we unhooked ours, it was ridiculous, other ways to heat without it costing an arm and a leg, we didn't install it, was there when we moved in,.

My uncle worked HVAC for 40 years he showed us where to turn off, but there should be a switch so that you can turn off (safety feature in case of emergency), it may look like a light switch. Once we turned it off our water bill went down and so did our power bill, even in Summer when you aren’t using for heat the hot water continues to run through the heat pump. Our power bill the one winter we used it was $450. Our cooling bill is $120 in the hottest months, our AC is a different unit. We now use 2 small heaters that we bought a Home Depot that look like wood burning stoves, but are electric, in the coldest months our bill has never been over $190. Heat Pumps do not save energy, nor do they provide comfortable heat. You will be much better off if you can get by with never using it.

Thanks! Great information! 👍🏼

I wish I could explain in detail, my uncle who isn't with us anymore did HVAC for 50 years and he showed us what to do, but there should be a main cut off switch near the unit, I would have to look at mine again to tell you specifics, but it will probably look like a light switch near the heat pump.