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Keeping the breaker and the power bill in check

The situation

Forty-eight printers draw a lot of electricity, in two very different ways. At the start of a print the bed heaters spike — a dozen beds climbing at once trips a breaker. At the end of a print nothing happens at all: the part cools, the printer sits powered with its screen on and its fans idling, and forty-eight of those add up to a heater's worth of nothing all night.

The bill arrives once a month with one number on it, and nobody can say what a lamp costs to print.

The goal

Three things at once: no breaker trips on a plate-change round, no printer idling powered through the night, and a kWh and a cost on every print — so the order page's Cost is a measurement, not a guess.

What is involved

Feature Its part
Staggered start Caps how many beds heat at once — the peak.
Smart plugs → Automation Auto Power Off after a print and cooldown; Auto Power On for the next queued print — the idle draw.
Per-print energy and Energy tracking The plug's meter read at print start and print end; the delta is the print's kWh, and × your rate is its cost.
Stats → Energy Lifetime and per-printer totals; the print / total switch.

Step by step

  1. A plug per printer, with a meter. Any of the supported plug types that reports energy — Tasmota, Zigbee, Home Assistant, MQTT, a REST plug with an energy URL. Link each plug to its printer and leave This plug powers the printer on; turn it off on accessory plugs (a filter, a dryer, the lights), otherwise switching the filter off would mark the printer offline.

  2. Cap the peak. Settings → Printing → Queue & Scheduling → Staggered Start: enable, Concurrent starts to what the circuit takes, Wait for bed to heat on. On a three-phase feed split it per phase — the whole recipe is Three phases, one bed heating per phase.

  3. Cut the idle. On each plug card: Auto Power Off with the cooldown threshold (default 50 °C bed) and a delay; Auto Power On so a queued print can wake the printer. Leave Keep enabled on the plug that runs the chamber heater or the room's HVAC — that one must not cycle.

  4. Put a price on a kWh. Settings → System → Energy: your rate per kWh. It is a plain multiplier — enter it in the currency you pay in.

  5. Choose what "energy" means. Settings → System → Energy display mode: print sums the per-print deltas — what did the prints cost; total reads the plug's lifetime counter — what did the printer's socket consume, idle included. The two diverge by exactly the idle draw you are trying to see.

  6. Read it back. Every archive card now carries the print's kWh and cost; the order page sums them into Cost and, with a price on the order, Margin. Stats → Energy shows per-printer totals for a date range, so the machine that idles most is the one with the biggest gap between total and print.

What BamDude does on its own after that

  • At print start the plug's meter reading is written onto the print's record. At print end the meter is read again — freshly, forcing a read on plugs that cache their values — and the difference is the print's kWh. A failed or cancelled print records what it burned up to the stop.
  • The baseline survives a restart. The start reading lives on the print, not in memory; restart BamDude mid-print and the end still computes the right delta.
  • Auto-off waits for four things: the bed below the threshold; the print not paused (resume or cancel it first); no pending job in that printer's queue — the next dispatch would only wake the plug again; and the plug not marked Keep enabled. From a failed or cancelled end it fires once the bed is cool, like from a completed one.
  • Auto-on switches the printer's power plug on when a queued print — including a scheduled one, at its time — needs the printer, waits for it to come up, and dispatches. Accessory plugs are never used to wake a printer.
  • A switched-off plug reports 0 W. Some cheap plugs keep reporting the last measured watts after the relay opens; BamDude does not pass that on. The lifetime counter is never zero-filled, so a plug that is off does not create a phantom consumption when it comes back.
  • Hourly snapshots of every plug's counter feed the date-range totals, and a counter reset (firmware flash, power cut) is clamped to zero rather than showing as negative energy.

Pitfalls and what-ifs

  • Stagger costs throughput on purpose. It spreads starts; a running print is never slowed by a neighbour waiting for a slot. If the circuit takes simultaneous heating, do not stagger.
  • Auto-off will not fire while the queue has work — that is a feature, not a fault: with the auto-queue feeding a printer all night, its plug stays on all night, and the idle saving comes from the printers that genuinely have nothing queued.
  • Print-hour maintenance intervals run on print time, not on plug time. Cutting power does not reset anything there.
  • A plug without a meter still switches, but leaves the print's kWh empty; the order's Cost then carries filament only for those prints.
  • The archive's kWh is the printer's kWh. A plug that also feeds the chamber heater or the lights measures them too. Put accessories on their own plug if the per-print figure has to mean the printer.
  • total can be smaller than print after a reset. A plug that lost its counter starts from zero; the per-print deltas from before are still on their prints. The date-range clamp keeps the total from going negative; it cannot invent the lost history.