Comcast on Monday announced that it will offer 5G for no extra cost across both its unlimited and "by the gig" service plans. The offer shines some daylight between the mobile strategies of Comcast and Charter Communications, which is noteworthy given how similar they are.

Charter switched on its own 5G offering in early March, but that service is restricted to its $45 unlimited plan and is not available on the operator's "by the gig" plans.

Although Comcast began selling the Samsung Galaxy S20+ and Galaxy S20 Ultra 5G-capable smartphones in March at the same time Charter did, it did not offer 5G. Instead, it said only that the service was "coming soon."

On Monday, 5G arrived at Comcast across both its "by the gig" and $45 unlimited plans. Company officials did not answer questions about the delay.

"From day one, Xfinity Mobile has been proud to be the only provider to empower customers to design a mobile plan that fits their needs, as well as have the flexibility to seamlessly switch between unlimited or per gig to save money," Comcast's Rui Costa, SVP of innovation and customer value propositions, said in a release. "We're excited to now extend that benefit with 5G data plans."

Existing Xfinity Mobile customers will need to opt in to a 5G data option through the Xfinity Mobile app in order to activate service.

Interestingly, Comcast increased the monthly price for its lowest "by the gig" plan. Prior to offering 5G, Comcast's 1GB mobile plan cost $12 per month. Now it's $15 per month. Company officials noted that existing customers can remain on the $12 option unless they want to upgrade to 5G.

Both Comcast (with its Xfinity Mobile offering) and Charter (with its Spectrum Mobile offering) piggyback on Verizon's 5G network. Thus, the cable companies' 5G is only available in the downtown areas of roughly 30 cities. That's because Verizon is deploying 5G on its high-band, millimeter wave (mmWave) spectrum, and signals in that spectrum can only travel a few thousand feet but can support blazing-fast speeds.

Verizon has promised to expand its 5G signal nationwide sometime this year by deploying the technology in its low-band spectrum. However, company officials have warned that low-band 5G won't provide the same kind of speeds that its mmWave 5G network supports.

Verizon, for its part, remains the only wireless provider in the US with plans to charge extra ($10 per month) for 5G.

Cable company Altice recently joined Comcast and Charter in the mobile industry via MVNO agreements with T-Mobile and AT&T. Altice offers 5G for no extra charge. Further, the company appears to have resurrected its $20 per month mobile offer after having discontinued it during the first quarter.

— Mike Dano, Editorial Director, 5G & Mobile Strategies, Light Reading | @mikeddano