There are a couple of questions I would ask you if I could. Since that is not possible, you will get two answers that will create some legwork for you.
The way you asked the question, from my perspective, suggests that you have a water-source heat pump for heating/cooling of your house. If that is the case, the answer to your question is a little complicated. Depending on the size of the tankless water heater and the size of the heat pump that conditions your house, I can give you a firm maybe.
Tankless water heaters are designed to save energy and money lost due to heat from storing "x" gallons of water waiting to be used. You should contact a local engineer or a contractor that has an engineer on staff to solve the engineering details.
The other question that is conspicuously absent from this conversation is "do you really want to connect a tankless water heater to your (what I am guessing is) house heating/cooling system (heat pump)?"
Keep in mind that a tankless water heater is designed to save money and energy because it only "runs" when you need hot water. If you have a water-source heat pump for your house, your water heater will run whenever the heater or the A/C runs, in theory. The reason is that a water-source heat pump expects water within a given temperature range to function at optimal efficiency.
If my answers are not what you expected, please feel free to contact me and explain what you really mean by this question.