Mea Culpa – my math was wrong

In my previous blog post, I tried to refute the idea that TV set top boxes are the second largest consumer of energy in many US homes. I wrote: “According to the reporter’s own data, the average set top box (STB) uses about 35 watts per hour while on standby. There are 224 million STBs in the US, and about 110 million homes, meaning the average home has two of these ‘power hogs.’ At 24 hours per day times two devices, that is 1.68 kWh per day.”

Bad Duncan. That was NOT what the reporter said: “A set-top cable box with a digital recorder can consume as much as 35 watts of power…”

Please note his two qualifiers. First, not all of the 224 million STBs in America have PVRs: in fact, only about 50% of pay TV homes have even one PVR. Second, that phrase “as much as” should have gotten my spidey-sense tingling. Based on people who measure their own PVRs, 25 watts standby power is the norm, with non-PVR STBs running about 15 watts standby.

Therefore, let’s assume that about 35% of all the STBs in the USA have digital recorders, or 78 million, consuming an average of 25 watts per hour. That leaves 146 million consuming 15 watts. The blended average is about 18.5 watts.

Therefore, in all my comparisons to other sources of energy consumption, the number for an average home with two cable boxes is NOT 1.68 kWh per day, but 0.888 kWh per day, or 47% less.

Which makes the idea that set top boxes in standby mode are a significant part of household energy consumption even more ludicrous.