I think I would make the PCs use a healing surge for each Encounter ability.
The reason behind this is that I've found my players don't ever spend their entire allotment of healing surges in a day. They can only spend 1 each encounter (so that's 4-5 in a day) and they never spend them outside an encounter unless they are really hurt (they usually just rest for closer to 20-30mins and just let the Cleric continuously use his healing word to heal them).
I think this would also help balance the ability at higher levels when the PCs will have more Encounter abilities.
The reason behind this is that I've found my players don't ever spend their entire allotment of healing surges in a day. They can only spend 1 each encounter (so that's 4-5 in a day) and they never spend them outside an encounter unless they are really hurt (they usually just rest for closer to 20-30mins and just let the Cleric continuously use his healing word to heal them).
I think this would also help balance the ability at higher levels when the PCs will have more Encounter abilities.