Pool owners who are considering a cleaning device often ask about electricity cost. It is a reasonable question. Anything that plugs into an outlet and runs for hours per week costs something to operate. The more useful question is not whether it costs money, but how much, and how that cost compares to the alternatives. The answer is more nuanced than the wattage rating on the product box suggests, because the actual consumption depends on the cycle length, the frequency of use, and the local electricity rate. The Numbers: Watts, Hours, and Dollars A typical robotic cleaning device draws between…