Power quality is the health of the electricity itself — how steady the frequency sits at 60 Hz, how clean the voltage waveform is, and how carbon-heavy each kilowatt-hour is right now. These are the same signals that tell a battery the smartest moment to charge or discharge.
In the United States the grid runs at a nominal 60 Hz (Europe uses 50 Hz). Frequency is a real-time balance of supply and demand: when generation exceeds load, frequency rises slightly; when load exceeds generation, it dips. Operators keep it inside a tiny band — typically within ±0.02 Hz — and treat sustained excursions below about 59.85 Hz as an emergency that triggers automatic load shedding.
Voltage at the wall is nominally 120 V in the US. ANSI C84.1 defines a normal operating range of roughly ±5% (about 114–126 V), with ±10% as the absolute service limit. Heavy demand causes voltage sag; light load late at night lets it recover. Sustained over- or under-voltage stresses equipment and is a core power-quality metric.
THD measures how far the voltage or current waveform departs from a pure sine. Non-linear loads — inverters, EV chargers, variable-speed drives — inject harmonics that distort the wave. IEEE 519 guides utilities toward keeping voltage THD low (commonly under 5–8% depending on the bus). High distortion overheats transformers and trips sensitive electronics.
Carbon intensity is how many grams of CO₂ each kilowatt-hour carries, set by the live generation mix. A grid running heavy on wind and solar at midday is far cleaner than one leaning on gas peakers at the evening ramp. The same swings that move carbon intensity also move price — which is exactly where a battery earns its keep.
Grid quality is not just diagnostics — it is the playbook for a battery energy storage system (BESS). When midday solar floods the grid, carbon intensity and wholesale prices both fall, frequency tends to firm up, and that is the window to charge cheap and clean. When the evening ramp hits and gas peakers spin up, carbon intensity and prices spike while frequency comes under pressure — the moment to discharge into the peak. A storage asset that reads frequency, carbon intensity and price together captures arbitrage value and displaces the dirtiest, most expensive megawatt-hours. That is the optimizer's job: turn grid-quality signals into charge and discharge decisions.
See the Stromfee Optimizer →