Cost for HVAC add refrigerant and leak sealant

[Peter Sik]

How much is usually cost for add refrigerant and leak sealant ?

[Tracy Streich]

depends on the type of freon.  R22 is anywhere from $85-200 per pound. 410a Is much less about $40-50 lb.   If you have an old unit it is likely R22.  The stop leak is about $200.   

If your unit is really old and you have the cash you might consider upgrading to new unit with 410a.  You can throw away a lot of money on freon if you have a leak.