The pitch is that the Internet of Things will make our world a greener place. Environmental sensors can detect pollution, the voices say. Smart thermostats can help us save money on our electric bills. A new breed of agriculture tech can save water by giving crops exactly the amount they need and no more. But this vast network of new online devices could also end up harming the environment. Manufacturing all those gadgets means expending both energy and raw materials. In many cases, they will replace an older breed of devices, which will need to be disposed of (so long, non-smart thermostat). And eventually, every IoT device you buy–and people are predicting there will be hundreds of thousands–will need to be retired too. Since all these devices will connect to the net, we should even consider the energy used by the data centers that drive them.