[generalpass]

You can run them on an old computer. Used mini-towers and desktop form factor can be had for close to free.

The next major release of pfSense will require hardware encryption support (e.g., AES-NI).

OPNSense is very reliable, but has fewer features though is in active development. Haven't used it in around 18 months or so.

I picked up an HP 4-port 1gbps PCIe card for $40.

[chopin]

However a router is energy sensitive as it runs 24/7. I wouldn't want to run a desktop for this.

[generalpass]

Just install a low power CPU. You can get one on eBay delivered for a little more than USPS 1st class shipping. Most of my devices, including my NAS, consume 25-35w, so up to 15w additional consumption, as checked with Kill-A-Watt.

Ever do a tiny load of laundry to get one shirt clean? You've just used something like a year of computer running.

Do you run your air conditioning while your refrigerator exhausts into your kitchen? I call that a kitchen heater. You're heating a cooled space.

I find for whatever reason, tech people all worry about the energy consumed by tiny devices.

[edgineer]

There are other power usage concerns beyond cost. For example, if a small room can't have air conditioning you might want only very low power devices to keep from heating it up.

[zrm]

~35 watts isn't actually all that much heat load, and that's what you get from the likes of a business-class Core i5 at the loads routing packets would put on it (i.e. basically idle). Something like Atom or AMD Bobcat is <15 watts.

Another thing to keep in mind if you're worried about power/heat is that 3.5" spinning rust can pull >5 watts per spindle. I've seen 15K drives pull close to 20. But an SSD is close to nothing and so are most 2.5" laptop spindles.

[generalpass]

I'll concede that a small closet can get pretty warm from even lower power devices. However, as long as the CPU isn't overheating and the space is clean and dry, it doesn't matter.