Using the LP405 well

Short, practical notes on metering, tariffs and heavy loads. These are the questions we get asked most often.

How time-of-use billing actually works

Your utility charges different rates at different hours — typically peak, shoulder and off-peak. The LP405 lets you enter all three, plus a schedule for each, and then accumulates cost as energy is used. The point is not the total; it is seeing which appliance pushes you into the peak price. Run heavy loads in shoulder hours and the same kWh costs less.

Sizing a smart plug for an AC or heater

Look at the appliance’s nameplate, not the marketing wattage. A heater sold as “2000 W” often draws more at startup, and an AC compressor can pull three to five times its running current for a fraction of a second. The LP405’s latching relay is rated for 25 A continuous with high inrush tolerance, but the wall circuit still has to be rated for the appliance. If your breaker trips, the plug is not the problem.

Reading the numbers: kWh → money

One kWh means 1 kW used for one hour. A 1,500 W heater running two hours is 3 kWh. Multiply by your rate to get the cost — then compare that against what the plug reports. A large gap usually means the appliance cycles less than you think, or your tariff period is set incorrectly in the app.

Offline logging

Insert a microSD card (up to 128 GB) and the LP405 writes readings locally even with no Wi-Fi. That history is what you want when a voltage sag or an outage damages a compressor and you need evidence for a claim.