ComputersDesktop
DELL QCT1255 Computer Manual
Setup, everyday use, maintenance and troubleshooting for the desktop computer, with verified specifications.
- ProcessorAMD Ryzen 7 8700G
- Memory64 GB
- Idle power16.5 W
- Est. yearly cost$8.98
About the DELL QCT1255
The DELL QCT1255 is a desktop computer certified under the ENERGY STAR program for computers. It is also identified as D34M.
The certified configuration includes an AMD Ryzen 7 8700G processor (8 cores, up to 5.1 GHz), 64 GB of memory, SSD + HDD storage across 2 drives, and discrete graphics, running Windows 11 or Ubuntu Linux. Retail configurations of the same model can differ, so check the system information on your unit.
Hardware listed in the certification record includes a 180 W internal power supply (89% efficient at half load) and a Gigabit Ethernet port.
Its typical energy consumption (TEC) is 52.8 kWh per year, 42% below the ENERGY STAR limit of 91 kWh for its configuration. Measured idle power is 16.5 W, and sleep draws 1.9 W. The TEC figure is lower than 35% of the 285 Desktop models in our database.
Specifications
| Brand | DELL |
|---|---|
| Model number | QCT1255 |
| Model name / series | D34M |
| Computer type | Desktop |
| Processor | AMD Ryzen 7 8700G |
| CPU cores | 8 |
| Base clock speed | 4.2 GHz |
| Maximum clock speed | 5.1 GHz |
| Neural processing unit (NPU) | No |
| Memory (as certified) | 64 GB |
| Storage type | SSD + HDD |
| Installed storage drives | 2 |
| Discrete graphics | Yes |
| Operating system | Windows 11 or Ubuntu Linux |
| Touch screen | No |
| Internal power supply rating | 180 W |
| Power supply efficiency at 50% load | 89% |
| Motherboard form factor | Standard-ATX |
| Gigabit Ethernet ports | 1 |
| Energy Efficient Ethernet | Yes |
| Wake-on-LAN (as shipped) | Enabled |
| Default low-power mode | Alternative low power mode (ALPM) |
| Sleep timer (as shipped) | 5 min |
| Display-off timer (as shipped) | 5 min |
| Short-idle power | 16.5 W |
| Long-idle power | 1.9 W |
| Sleep power | 1.9 W |
| Off power | 0.3 W |
| Typical energy consumption (TEC) | 52.8 kWh/yr |
| ENERGY STAR TEC limit | 91.0 kWh/yr |
| Below ENERGY STAR limit | 42% |
Safety information
- Connect the computer to a grounded outlet, preferably through a surge protector. Replace a damaged power cord before further use.
- Shut down and unplug the computer before opening the case. Touch a bare metal part of the chassis (or wear an antistatic wrist strap) before handling memory, drives or expansion cards.
- Keep liquids away from the keyboard and vents. If liquid is spilled, shut down immediately, unplug the power and let the computer dry completely before restarting.
Setup
- Unpack and inspect
Remove all packaging, protective film and cardboard inserts. Keep the box and receipt until you are sure the computer works correctly.
- Choose a location
Place the system unit on a stable surface or the floor with at least 4 in. (10 cm) of clearance around the vents. Avoid enclosed desk cabinets and carpet, which restrict airflow and collect dust.
- Connect a monitor
Connect your monitor to the video outputs on the discrete graphics card (usually lower on the back panel), not the motherboard ports, or you may get no picture.
- Connect peripherals and network
Connect the keyboard, mouse and any USB devices. For the most reliable connection, plug an Ethernet cable into the network port. Then connect the power cord.
- Complete operating system setup
Follow the Windows setup screens to choose your region, connect to Wi-Fi and sign in. Then open Settings > Windows Update and install all available updates, including optional driver and firmware updates.
- Update firmware and drivers
Use the manufacturer's update utility or support page to install the latest BIOS/UEFI firmware, graphics driver and chipset drivers. Keep the computer plugged in during firmware updates.
- Set up backups
Turn on cloud sync or connect an external drive and schedule automatic backups before you store important files on the computer.
Using your computer
Sleep and power settings
As shipped, the DELL QCT1255 turns off its display after 5 minutes of inactivity and goes to sleep after 5 minutes. Keeping these timers short is the easiest way to save energy. Its default low-power state is an alternative low power mode (ALPM), a reduced-power idle state used in place of conventional sleep; it resumes almost instantly. Measured sleep power is 1.9 W, compared with 16.5 W when idle with the screen on.
Performance
Discrete graphics (8 GB/s frame-buffer bandwidth, as certified) accelerate games, 3D and video work but add to power draw. With 64 GB of memory, the system has ample headroom for heavy multitasking, large photo or video projects and virtual machines. Solid-state storage needs no defragmenting; leave 10–20% of the drive free so it can maintain performance.
Networking
The computer has one Gigabit Ethernet port. Energy Efficient Ethernet (IEEE 802.3az) lowers link power during quiet periods when the switch also supports it. Wake-on-LAN from sleep is enabled as shipped; IT departments use it to wake computers remotely for overnight updates.
Care and maintenance
| When | What to do |
|---|---|
| Weekly | Restart the computer to apply pending updates and clear memory; confirm that backups completed. |
| Monthly | Install operating system and application updates. Wipe the keyboard, mouse and case with a soft, slightly damp microfiber cloth (power off first). |
| Every 3–6 months | With the computer shut down and unplugged, clear dust from the front and rear vents and, if comfortable, inside the case around fans and heat sinks. |
| Every 6–12 months | Check for BIOS/UEFI firmware updates from the manufacturer and review storage health and free space. |
Troubleshooting
Start with the simple checks below. For beep codes, diagnostic lights or error messages specific to this model, use the manufacturer's built-in diagnostics and support documentation.
| Problem | Possible cause | What to try |
|---|---|---|
| Will not turn on | Power cord or outlet; power strip switched off. | Check the outlet and power strip, reseat the power cord, then hold the power button for 15 seconds and try again. |
| Runs hot or the fan is loud | Dust-clogged vents; blocked airflow; heavy background task. | Clean the vents, keep 4 in. of clearance around the case, and check Task Manager for apps using a lot of power. |
| Slow performance | Too many background apps; storage nearly full; pending updates. | Close or disable unneeded startup items, free up storage space, install updates and restart. |
| Will not wake from sleep | Software or firmware issue; accessory preventing wake. | Press the power button briefly; update chipset, graphics and firmware; disconnect USB devices to test. |
| Wi-Fi drops or is slow | Weak signal; outdated software; router issue. | Move closer to the router, update the network driver, and restart the router. |
| No picture on the monitor | Monitor connected to motherboard video instead of the graphics card; wrong input. | Move the cable to the graphics card output and select the correct input on the monitor. |
Energy use and running costs
The DELL QCT1255 has a typical energy consumption (TEC) of 52.8 kWh per year, about $8.98 a year at $0.17 per kWh. TEC combines the measured off, sleep and idle power with ENERGY STAR's standard assumptions about how many hours a year a desktop spends in each state. It does not include time under heavy load such as gaming, rendering or video export, which can draw several times the idle figure.
| Power state | Measured power |
|---|---|
| Short idle (on, screen on, nothing running) | 16.5 W |
| Long idle (display off) | 1.9 W |
| Sleep | 1.9 W |
| Off (plugged in) | 0.3 W |
Sleep settings matter: leaving the computer on and idle for the 16 hours a day you are not using it adds about 96.4 kWh ($16.38) a year, versus 11.1 kWh ($1.89) if it sleeps during those hours.
Frequently asked questions
What processor and memory does the DELL QCT1255 have?
The certified configuration has an AMD Ryzen 7 8700G processor with 8 cores (up to 5.1 GHz) and 64 GB of RAM. Other retail configurations may differ.
How much electricity does the DELL QCT1255 use?
Its ENERGY STAR typical energy consumption is 52.8 kWh per year — about $8.98 at $0.17/kWh. It draws 16.5 W at idle and 1.9 W in sleep.
What operating system does the DELL QCT1255 run?
It was certified with Windows 11 or Ubuntu Linux.
Does the DELL QCT1255 have an NPU for AI features?
The certification record does not list an installed NPU for this configuration. If on-device AI features matter to you, check the processor specifications for your exact unit.
Sources and disclaimer
Specifications on this page come from the ENERGY STAR certified computers dataset published by the U.S. Environmental Protection Agency (record certified March 12, 2025), retrieved October 7, 2026.
The setup, operating, maintenance and troubleshooting guidance is written by ManualHarbor's editors for this specific product type and configuration. It is an independent guide — not a reproduction of the manufacturer's manual — and ManualHarbor is not affiliated with DELL. Always follow the safety instructions, installation requirements and warranty terms supplied with your unit, and contact DELL or an authorized service provider for warranty repairs and replacement parts.
Running-cost figures use assumed U.S. average utility prices and are estimates for comparison only. See our editorial methodology for details.
Report a problem with this guide
Spotted a wrong value, a broken link or something unclear? Tell us and we will review it.