Purposely undersizing the heat pump doesn't make much sense to me.
Please explain to me what an undersized heat pump would be. The only thing we ever heard size-wise was we have a 5 ton unit. We talked to a couple of geo people before we did this and all they ever talked was tonnage.
Heat pumps come in various sizes from small units for home to large units for apartment buildings.
The reasoning is that smaller heat pump is cheaper, requires smaller less expensive heat exchanger and cycles less at warmer temperatures. Supplemental heaters operate only limited time during temperature extremes. This is European customary set up.
We have 100% sized unit that cycles during warmer weather and runs almost constantly during very low ambient temperatures. We also have supplemental heaters in the heat accumulator but the breaker is turned off already for several years and the heaters will be used only during malfunction of the HP.
