The budget is based on kilowatt hours (the default value is 30 kWh/month, but you can change this as well as the beginning of your utility's billing period). The app will issue a warning when you near that limit (default value is 80 percent, but you can change it to whatever you like). This is a good idea in principle, but you'd need to have Smart Plugs controlling a majority of your home's lighting and appliances for it to really make a difference. And in my home, most of my lights are in the ceiling and controlled by wall switches.
You can also program schedules when the Smart Plug will turn on and off. The Home and Away settings will be enough for most people, but D-Link provides three custom schedules as well. You choose which one you want to be active. The app has time-zone settings, but no controls for turning the Smart Plug on at dusk or off at dawn, and you can't set "about" rules that would slightly vary the times the Smart Plug turns a lamp on or off in order to make it look as though someone is actually at home.
If you're using the Smart Plug for home-security purposes--to fool a would-be burglar who's casing your home into thinking someone is inside it--lights going on and off on a rigid schedule is a dead giveaway to any smart criminal. People aren't robots. And as you've probably guessed, there's no support for advanced features such a geofencing, where lights automatically turn on and off based on the physical location of your smartphone.
Is it worth buying?
Getting the most out of the D-Link's Wi-Fi Smart Plug means confining yourself to D-Link's walled garden of devices and apps and controlling it with your smartphone or tablet. Be sure to read my review of D-Link's DCH-S150 motion detector to see how that device can trigger the Smart Plug, too.
I do think D-Link is making a mistake in not following Belkin's lead and embracing the IFTTT (If This Then That) service. It would remedy some of the Wi-Fi Smart Plug's limitations while requiring very little effort on D-Link's part. As it stands, D-Link's device has little to recommend it.
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