Replacing very old system

[MB34]

My in-laws have a system, not sure what it is as it is so old that the nameplate is not easily made out.

I can make our this:
REAB-Y4150

I'm assuming it is a Rheem. Don't know capacity or anything else.

Can someone help out?
I need this info to get a replacement system that matches or beats this one as their electric bills are sky high because of this.

Can you recommend a replacement system for a 900-1000sqft (single story, not well insulated, built in 1954) house? I'd prefer
a unit that we can install in the attic space.

[ampulman]

My in-laws have a system, not sure what it is as it is so old that the nameplate is not easily made out.

I can make our this:
REAB-Y4150

I'm assuming it is a Rheem. Don't know capacity or anything else.

Can someone help out?
I need this info to get a replacement system that matches or beats this one as their electric bills are sky high because of this.

Can you recommend a replacement system for a 900-1000sqft (single story, not well insulated, built in 1954) house? I'd prefer
a unit that we can install in the attic space.

If it's that old, anything you get will beat it.

To determine what you need, a proper heat calculation should be done and the duct system evaluated.

AM

[MB34]

The ducting will all be replaced. I also intend to redo the insulation in the attic.
The walls cannot be insulated without replacing the siding or walls. Several
windows leak and they are also going to be replaced.

[Daltex]

You can blow insulation into each stud space to insulate the walls but $$ vs. return may not be worth it. The attic is the best money spent and look at radiant barrier and good ventilation. As said before: Load calculation, ductwork sized and sealed and then any new unit will save you a ton of cash. Installing it in the attic isn't the most efficient place but may be the only place. Is there an alternate place for it in a closet of something?

[MB34]

<SNIP>Installing it in the attic isn't the most efficient place but may be the only place. Is there an alternate place for it in a closet of something?

We want to reclaim the space that it takes up now. It is in a storage/laundry area off the kitchen that is only accessible from the outside. We want to be able to take that out, then remodel the area to be an extension of the kitchen.
Current layout:


new layout: