We have a Heat Pump and were told to run Emergency Heat Only below 30 degrees F for efficient use? Please help?

i will ume your heat pump has nothing wrong with it and isnt set to defrost any more often than 90 minutes intervals,,unless it has "demand defrost" which is better than "timed defost".....anyway,,heat pumps run all the time in heating mode when its cold because they are sized for COOLING, not heating....if they were sized for heating they would be way oversized for cooling and would have to move too much air for heating......the heat output of the heat pump decreases with outdoor temp...the houses heat requirement goes up as outdoor temp drops...the outdoor temp at which the heat pumps heat output equals the houses heat requirement to maintain your tstat set temp is known as the balance point.....at the balance point the heat pump will run all the time with no temperature change [ higher or lower] in the home.[ usually around 30-35 deg],,...below the balance point the heat pump will run all the time and the home's temp will still slowly drop..when the home temp drops despite the heat pump running all the time,the tstat turns on the "auxillary heat",which is usually electric strip heaters in the indoor unit...the heaters are only kept on long enough to raise the temp near the setting,but not enough to satisfy the tstat,just keeps the house temp from falling too far below the set temp..so during very cold weather you typically have the heat pump on continuously with occasional help from the auxillary heaters,,this is normal...its true the heat pumps efficiency decreases as outdoor temp decreases,but it is still more efficient than strait electric heat...strait electric heat has a 1 /1 c.o.p. [ coefficient of performance ],meaning for every watt of electricity,you get a watt of heat....a heat pump has a c.o.p. of 3 / 1 at 45 degrees outdoor vtemp...the heat pump's c.o.p.drops gradually as outdoor temp drops....its around 1.5 / 1 at around 15 degrees outside,,so its still more efficient than strait electric heat BUT it isnt bringing in very much heat relative to the home's needs,,so you have to factor in wear and tear and the lack of comfort with a system that is always on and blowing luke warm air....i would say use the heat pump in regular heat mode at least down to 20 degree's outside...below that use your best judgement...but switching to emergency heat just because the outdoor temp is below the balance point will cost you more than just letting the heat pump run and be isted by the auxillary heat......additionally,the statement that electric heaters are 100% efficient is correct but misleading...it just means that none of the heat is vented to the outside like it is in the case of gas or oil heat....a 70%eff natural gas or oil furnace is MUCH cheaper to run than a "100%" eff electric furnace [strait electric heaters,not talking about a heat pump]...just look at the yellow energy guide sticker on a natural gas water heat vs an electric water heater...the electric water heater costs around 3 x what a 70% eff nat gas water heater costs to run.. its better to compare the c.o.p. when looking at heat pump vs strait electric heat............dan