> Other than higher cost for the heat pump unit, are there any other issues with having one that's oversized for heating?
- Short cycling leading to lower equipment life (also true for gas furnaces, although heat pumps have more moving parts)
- Greater discomfort as the house heats up rapidly then cools down rapidly (especially if it has a leaky building envelope).
- Higher peak electric loads, possibly during hours of high electricity prices, leading to higher electricity costs.
> My understanding is that for cooling, having one that is oversized can be a problem because of humidity issues,
Yes, because moisture will build up when it isn't running.
> makes me wonder what can be done if a space has an imbalance between the size needed for cooling versus what it needs for heating.
Many heat pumps have different output ratings for heating and cooling modes to deal with this. Often however, this has as much to do with the distribution of the heated/cooled air and placement of supply registers, which is often an afterthought when the system is purposely oversized (which is presumed to make up for lack of air distribution design).
- Short cycling leading to lower equipment life (also true for gas furnaces, although heat pumps have more moving parts)
- Greater discomfort as the house heats up rapidly then cools down rapidly (especially if it has a leaky building envelope).
- Higher peak electric loads, possibly during hours of high electricity prices, leading to higher electricity costs.
> My understanding is that for cooling, having one that is oversized can be a problem because of humidity issues,
Yes, because moisture will build up when it isn't running.
> makes me wonder what can be done if a space has an imbalance between the size needed for cooling versus what it needs for heating.
Many heat pumps have different output ratings for heating and cooling modes to deal with this. Often however, this has as much to do with the distribution of the heated/cooled air and placement of supply registers, which is often an afterthought when the system is purposely oversized (which is presumed to make up for lack of air distribution design).