problems with current approach
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The problem of the current systems in not entirely the fault of homeowners or of HVAC contractors up-selling to dual fuel. It is more systematic. As an builder I am a member of the MassSave Heat Pump Installers Network (HPIN). Some of the training is very good, but there are problems. The industry itself has not done a good job of addressing the particular challenges of good system design for New England. When you do heat loss/gain calculation in NE it turns out our peak btu's/hr heating requirements far outstrip our cooling requirements. Putting in systems that actually will cover 100% of our heating load is discouraged by ASHREA since that will result in systems oversized for cooling, which means on modestly hot days (~80F) the systems are short cycling and unable to successfully dehumidify the air. So homeowners are sold downsizes systems that don't cover the heat load + backup heat (usually fossil fuel) or they are given the option to buy a whole home dehumidification system and live in a house where we never open our windows.
As installers we are told we cannot trust our customers to open their windows when it cools of in the evening and close them and turn on the AC only when it is hot outside. System manufacturers tend to design for a 'keep you windows closed' type house, so systems are not programmed to run fan only for 15 minutes on shutdown which would successfully eliminate any condensation on the coils.
It's not rocket science and over the last few years of heat-pump only HVAC systems, my tenants have learned what they need to do to keep the systems operating well in both summer and winter.
