Heat pumps take a good amount of time to raise temperature. I never recommend a set back thermostat be used with a heat pump. Never expect a heat pump to heat as well and as fast as gas so you might as well adjust to the situation.

Many years ago when a customer would complain about how long the heat pump took to heat up we just used to bridge in a 5 kw heat strip to run with the heat pump. It solved the slow heat problem but did not help the electric bill.

Since we are not there to run a actual test on your system you will have to trust the dealer you chose to do the work. I am sure you got 2 or 3 estimates and checked out how good the companys work was before you hired them.

Thanks to hvac1000, T-Top and letmetellu for enlightening me about heat pump operations. But doesn't that go against good 'energy conservation' procedures? For the past 10 years, to 'conserve energy,' I've been using a programmable thermostats on my furnace to regulate the temperature 4 times daily: set back the temperature at night to 60F, up to 66F before going to work, down to 62 during the day, then up to 66 for an hour or two before bedtime. Ditto with summer AC procedures. Is there a compromise between HP efficiency and 'green thinking?' ILS^2

I have a heat pump myself and yes it does take a while longer to raise the temperature after set back. But it usually averages no more than 5 degrees a minute [actually, 5 minutes for one degree]. I wonder if your house is in need of more insulation, better windows, etc. Heat pumps certainly don't put out the heat of gas units, but then again if the house is adequately sealed and insulated the heat pump should take care of your heating needs. And as far as set back, this is the first year I have used a set back thermostat....mostly for the reason I prefer it to be cooler at night, when I sleep. I doubt I will use it for the cooling season. Another thing to consider is that some thermostats will call for aux heat if there isn't a heat rise in a certain period of time. Does your thermostat provide that feature? Does your furnace have aux heat (2nd stage)? Any heat pump installed in areas that can get below freezing have to have that feature, for the simple fact that during defrost cycle the aux heat is needed to prevent the house from being cooled. Hope I have helped in some way.

....My HP is installed in a small, unheated space under a sloping roof. Below is a 1st floor bedroom and behind it, a 2nd floor bathroom. But aren't all HPs (the air handler, not the exchanger) in unheated areas?

A clue. It's in an unheated space. Have you checked the air handler and return ductwork and make sure it's sealed up air tight? I ran a call last month with the same symptoms, and found the filter door off of the air handler which was under the house. The filter door being off, the cold air under the house was being sucked into the air handler-effectively killing the heat (first bad cold spell this year)! If it's flex duct, make sure it's all intact and none of the returns have slipped off their boots. If it's metal, make sure all joints are tight and sealed with foil tape-this will also keep critters out of your ductwork.

Why wouldn't you have control over the second stage? Your thermostat should provide that with switching. The second stage is the strip heater that should energize if the HP is not keeping up. What type of T-stat do you have......make, model #?

The unit is brand new and just installed last month. Everything is very well sealed, including the door. ILS^2

I would without hesitation contact the installing contractor and explain my concerns. There should be NO reason a brand new system fresh out of the box can't keep up with the heat loss of an average home if it's properly sized.