Over the past twenty years I have seen and implemented several different methods of tracking and billing for technology fees. The most basic method would be to charge a fixed Job Cost allocation each month based on some other factor on the project such as total job value, total labor cost, etc. And while this method can recover the technology costs for the project, it is often challenged on T&M jobs or any project that requires substantiation of costs for billing purposes because it fails to provide the level of detail often required.
If you have a lot of jobs that require billing backup, or substantiation, then I would suggest implementing a system where the technology is setup at its own equipment department. Each piece of technology is tracked for both cost a revenue and billing rates to jobs are based on cost to purchase and maintain each type of technology throughout its life. The technology is often assigned either to an employee and billed to the job automatically based on the number of hours that employee charges, or the equipment is assigned and charged directly to the job. This method gives the required detailed documentation for billing backup on substantiated jobs to ensure your company is compensated for the technology.
I have seen any number of other methods throughout my career, but the two above are the most common. If you would like to discuss this further, please just reach out to me via the number in my signature block. I am always happy to help where I can.