I think amazon has a pricing error on their website for the light utilization instances since the April price drop as they are more expensive than even the on demand ones (at least the ones I looked at).
I submitted a support ticket but haven't heard anything back. Once you start looking at medium reservation the prices fall significantly.
For example for the 3.75GB m3.medium is $51.1 on demand per month vs ~56 for the light reservation vs ~35 for the medium reservation. All running 24/7 and 1 year terms on reservations.
EDIT: Just got a reply on my support ticket. I guess the light reservation instances are just for reserving capacity now.
"You are correct about the Light Utilization Reserved Instances. I have brought this to the attention of the EC2 pricing team to see if this is an error on our part. Unfortunately, these Reserved Instance types now only cover Capacity Reservation and no longer offer a discounted hourly rate over the On Demand hourly prices."
I submitted a support ticket but haven't heard anything back. Once you start looking at medium reservation the prices fall significantly.
For example for the 3.75GB m3.medium is $51.1 on demand per month vs ~56 for the light reservation vs ~35 for the medium reservation. All running 24/7 and 1 year terms on reservations.
EDIT: Just got a reply on my support ticket. I guess the light reservation instances are just for reserving capacity now.
"You are correct about the Light Utilization Reserved Instances. I have brought this to the attention of the EC2 pricing team to see if this is an error on our part. Unfortunately, these Reserved Instance types now only cover Capacity Reservation and no longer offer a discounted hourly rate over the On Demand hourly prices."