Whenever we try to bag a bargain we usually have to accept a little more responsibility. This is the case with wholesale heat pump shopping - the responsibility is to know what you want. There will be no salesman to help you out (some may think that is a good thing), so if you choose the wrong unit, you have only yourself to blame.
If the unit does not work as it should, you are still protected by consumer laws (unless you bought it illegally, in which case you have no protection and do not deserve any). So the thing you need to worry about is making the right choice.
Do some investigation - it is definitely worth it, and in this Internet age, it is not difficult. A good start is the web page of a big manufacturer. If you dial up lennox heat pumps or goodman heat pumps you will be able to learn enough to sound knowledgeable and should be able to find out what you are looking for.
You will know how heat pumps work with really high registered efficiencies - you will see things like 400% efficient... This is because the pumps gain free heat (as it were) from the environment. It is one of the key reasons for switching to these units.
But there are other things that you might forget to consider - what about noise? Many people live in peaceful suburban areas and a night enjoy lovely silence. You do not want your heat pump to destroy the calm, so check out the noisiness too.