Add your router, server, TV, or any appliance. Use the watts on a power meter for the best estimate. Everything is calculated in your browser.
Monthly electricity cost
Add a device to see your total.
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Device estimates are saved on this browser. Each device keeps the electricity rate entered when it was added. Off hours are treated as zero watts; include standby use in idle hours when needed.
Compare the cost of keeping your device with buying a replacement. Use average watts for the same job and the same daily schedule.
Example inputs: 200 W versus 40 W, running all day, with a $300 replacement. Change these to match your equipment.
Lower total cost with replacement
Electricity savings cover the purchase price within this period.
Daily energy (kWh) = watts × hours ÷ 1,000. The device list splits active and idle hours. Annual electricity cost = daily kWh × 365 × rate in cents ÷ 100. Monthly estimates use 30.44 days.
Replacement payback (months) = replacement price ÷ annual electricity savings × 12. There is no electricity payback if annual savings are zero or negative. Total savings over the selected period = current electricity cost − replacement electricity cost − replacement price.
Both devices use the same daily schedule and a constant electricity rate. Off hours are treated as zero watts. Repairs, financing, resale, cooling effects, rate changes, and device failure are excluded. For a 24-hour measured average, set hours to 24. These calculations describe the inputs; they do not establish that two devices have equivalent performance.
Source for energy units: U.S. Energy Information Administration — measuring electricity.
An equipment rating describes a limit or a rated condition. A measurement tells you what your device uses during your workload.
For a plug-in device, choose a meter that records cumulative kWh and is rated for its voltage and load. Follow its instructions; ordinary plug-in meters are not for hardwired circuits.
Record energy over a representative day or several days. Average watts = measured kWh × 1,000 ÷ measured hours. For example, 2.4 kWh over 24 hours is an average of 100 W.
Add the variable supply and delivery charges that apply to each kWh. A fixed monthly service charge will not fall just because a device uses less energy.
If your rate changes by time of day, use a rate weighted by when the device runs. The example 18¢ rate is not a quote from your utility.
A replacement needs to do the same job. Compare similar workloads and include purchase and setup costs. An efficient device can still cost more overall when the purchase price is high.
If payback takes longer than you expect to keep it, electricity savings alone do not cover the upgrade in that period.
Meter feature reference: P3 International's cumulative kWh meter specifications. This is a manufacturer reference, not a tested product review or an affiliate link.