This self-hosted energy calculator adds up what your homelab really draws from the wall. Pick your hardware across four tiers, from a single Raspberry Pi to a stack of AI GPUs, set how many of each you run, and watch the totals update live: watts, monthly kWh, electricity cost, and yearly CO2.
The estimate is deliberately simple: a flat price per kWh (no tiered or time-of-use tariffs), no PSU conversion losses, a 730 hour month, and no datacenter overheads like PUE or embodied carbon. Systems are counted as whole-box wall power; GPU cards are counted as card-only draw on top of a host system, at stock power limits. Real inference rigs often run power-limited, an RTX 3090 capped to about 275 W loses almost no tokens per second, so the load numbers here are the ceiling, not the floor. The duty cycle assumes your gear runs 24/7, idling most of the day; move the slider if your machines work harder. Measured wall numbers from a Kill-A-Watt or a smart plug always beat any preset.
Formula: daily kWh = (idle W x idle hours + load W x load hours) / 1000, scaled to a 730 hour month. Cost = monthly kWh x your price. CO2 = yearly kWh x grid intensity. Price presets are household averages in USD (Eurostat, 2025); CO2 intensities are from Ember.