Can you run PoE Cat6 alongside standard Cat6 cables?

Yes. But you should be running Cat6A cable because of heat dissipation not interference (see later).

Notes:

Cat6 can be shielded or unshielded. Shielded will clearly be better.
Cat7 has an overall shield as well as individual shielding of every pair (so may be even more suitable).

Twisted pair cables are HIGHLY resistant to interference pickup. Furthermore, DC does not cause interference, since it is basically an unchanging current, so there's no change in magnetic fields from it to cause interference (other than when turned on, and off - and the twisted pair cables will reject that interference by design, anyway.)

I have many bundles of cables including POE cables in my work role. Interference is not a factor.

Source data wiring - Can PoE cause interference with neighboring non-PoE Ethernet cables? - Home Improvement Stack Exchange

You should be running Cat6A cable

In fact, a new PoE standard, IEEE 802.3bt, supports up to 100W of power per cable.

But higher power levels running through a cable can cause performance issues – namely by making the cable hotter. And when the cable gets hotter, insertion loss increases. This escalates your chances of your business experiencing a productivity killer – downtime – and may also damage the cable itself.

You’re better off using Category 6A for a number of reasons we’re going to cover here.

Larger-Gauge Diameter

A cable that offers a larger conductor diameter can reduce resistance and keep power waste to a minimum because it has a lower temperature increase compared to smaller-gauge Category 5e and Category 6 cables. This better performance will provide additional flexibility, including larger bundle sizes, closed installation conditions and higher ambient temperatures.

For example, when comparing 23-gauge and 24-gauge cabling, there is a large variance in how power is handled. As much as 20% of the power through the cable can get “lost” in a 24-gauge Category 5e cable, leading to inefficiency.

Less Power Loss

Energy efficiency increases when structured cable maximizes the power running through it to waste as little as possible.

As we mentioned above, losing nearly one-fifth of the total power in a 24-gauge Category 5e cable may seem like a lot of power loss – and it is. But doing the math will show you that the total dollar amount comes out to be only around $7 per year. The numbers start adding up; however, when you realize that it costs $7 per year per PoE device across your entire facility or campus – from surveillance cameras to wireless access points. Although it may seem like a small dollar amount when viewed out of context, power dissipation through a cable can ultimately lead to higher-than-necessary operating costs.

It’s also important to keep in mind that the number of Power over Ethernet devices is only going to increase in your facility as you install more wireless access points to support things like BYOD (bring your own device). As a result, you’ll need more PoE cable – and there will be more opportunity for wasted energy.

Less power is dissipated in a 23-gauge Category 6A cable, which means that more of the power being transferred through the cable is actually being used, improving energy efficiency and lowering operating costs.

Tightly Packed Cables

If your cables are tightly packed in their trays and pathways, the chance for heat increases because it doesn’t have a chance to dissipate away from the cable.

Some Category 6A cable has enough insertion loss margin to handle the extra heat generated from tightly packed cables without impacting performance. (This doesn’t apply to all Category 6A cables. Even though they promise a 100 m solution, some cables may become an 85 m solution if the temperature increase is too high.)

Belden 10GXS cable can handle the added heat while maintaining its full 100 m performance – and it’s the only Category 6A cable that can make this claim.

Source 3 Reasons Why Power over Ethernet Demands CAT 6A Cable

4Great answer. One nitpick though - the cost of cable loss figure seems unrealistic in practice as it assumes all poe devices are running at 100 watts all the time and they are all at the end of a long run. ( loss is related to distance of cable and amount of power drawn through it). Also, very few devices would draw anything like 100 watts. Most devices (phones , cameras for example) manage fine in under the 15 watts or so allowed by the 802.11af standard) – davidgo – 2019-06-30T19:54:41.360

2@davidgo Yeah, but cost is not the only criteria ... and if you replace those devices later with ones requiring more power you won't have to rerun new cables ... – DavidPostill – 2019-06-30T20:08:21.563

2100W is a lot of power. You could power 2 laptops with that! Typical devices like cameras only need 1/10th of that. – Navin – 2019-07-01T05:39:51.730

It's worth mentioning that this answer 100% applies to 10/100 Poe Ethernet, However gigabit and beyond uses all the pairs. Both ends, client device and power supplying devices have transformers in the circuit, which does means changing current (pulsed dc.). Because of differential signal techniques it shouldn't interfere with other Ethernet cabling. Old analog phone lines (cat-3) or other older analog circuits should be installed 12" or more away from a bundle of Ethernet cables using the newer Poe. – Tim_Stewart – 2019-07-01T13:55:01.093

Thank you for the very comprehensive answer! – Steve – 2019-07-18T20:31:45.800

6Any specific reasons why you think they couldn't be? – user1686 – 2019-06-30T11:55:51.743

@grawity - In the US code doesn't let you run power and communications in same conduit. See here. Whether this applies to PoE I've no idea.

– lx07 – 2019-06-30T12:21:10.927

7If this is a legal question about the US code that applies to installations in buildings, I'd assume it is off-topic here. – dirkt – 2019-06-30T12:24:37.757

4It's primarily a question as to weather the PoE signal will cause any interference / or speed degradation to the other cables as it has power running through it as well. i.e. 4k over HdBaseT Cat6 – Steve – 2019-06-30T13:57:26.843

4PoE signal? PoE is just plain DC voltage. It doesn't work the same way as AC power, and doesn't really constitute a "signal" in the way you're describing. – user1686 – 2019-06-30T20:15:44.703

1@grawity, take a toner and put it next to recent POE devices. (Gigabit Poe). You will find it's pulsed DC, and quite noisy. I can pick up the pulse almost three feet away from Ethernet coming from my Cisco small business switches at home. If you look further, they use phantom transformers on newer Poe circuits, this implies either AC, or pulsed DC. Otherwise the transformers would have no use. – Tim_Stewart – 2019-07-01T13:26:05.620

The transformers are for the balanced Ethernet signal not the POE. – Matthew Whited – 2019-07-01T17:39:12.960

And that pulsed RF emission is the Ethernet signal which is what causes the cross talk in the first place. – Matthew Whited – 2019-07-01T17:40:39.690