Running Microsoft Windows 7 Home Premium on a HP Laptop. The system tray power meter never shows the time remaining in the system tray. Only really ever show a percentage remaining number as pictured.
The windows help documentation on the "battery meter" seems to indicate that it should display a time remaining indicator, is this accurate?
How accurate is the battery meter?
The accuracy of what the battery meter reports—what percentage of a full charge remains and how long you can use your laptop before you must plug it in—depends on several factors. Most of these factors fall into the following two categories:
What you use the laptop for. Because some activities drain the battery faster than others (for example, watching a DVD consumes more power than reading and writing e‑mail), alternating between activities that have significantly different power requirements changes the rate at which your laptop uses battery power. This can vary the estimate of how much battery charge remains.
Battery hardware and sensor circuitry. Newer, "smart" batteries are equipped with circuitry that calculates the measurements of charge remaining and reports the information to the battery meter. Older batteries use less sophisticated circuitry and might be less accurate.
Best Answer
Finding the time remaining on your battery charge is actually a function of the hardware, not Windows. Windows queries the hardware for the time, via the ACPI. If this data is not provided, then Windows will not report a time. This is probably because the hardware would be the best place to determine such information, as it has direct knowledge of the battery info and amount of power draw.
This may be typical of HP laptops. My HP Pavilion tx2500z also did not support reporting this data. I found that it actually didn't have much when it comes to ACPI (I discovered this when attempting to install Linux and finding myself having to call the kernel with custom options).
Windows 7 does not attempt to estimate a value for time remaining if it cannot ask for it. However, the widget suggested by @user124759 does have this capability. It probably isn't as accurate, but is a worthy replacement.