> ## Documentation Index
> Fetch the complete documentation index at: https://docs.spirii.com/llms.txt
> Use this file to discover all available pages before exploring further.
# Grid balancing
> Earn from your portfolio's flexibility.
Grid balancing earns you revenue for making small, brief adjustments to charging power when the electricity grid needs them.
## Overview
An electricity grid stays stable only while production and consumption match. When they do, frequency sits at 50 Hz. Fossil production made that straightforward: if consumption rose, you burned more fuel. Wind and solar do not take instructions, so production has become the unpredictable side of the equation.
Flexibility has therefore moved to consumption, and EV chargers are unusually well suited to providing it. Trimming a charger from 11 kW to 9 kW for a few seconds is immaterial to the driver. Aggregate that across thousands of chargers and it becomes a resource a transmission system operator (TSO) will pay for.
Grid balancing is how your portfolio sells that flexibility. Spirii offers two services, and the difference between them is how the adjustment is triggered.
A reflex. Each charger reacts to the frequency it measures itself, cutting power within 30 seconds when the grid drops below 49.5 Hz.
A setpoint. The TSO sends a target every few seconds and the portfolio tracks it, holding reserve headroom to move within.
Grid balancing works across your portfolio to earn revenue. The local energy management capabilities — load balancing, price optimised charging, prioritised charging, programmatic charger control — work at a single site to cut energy costs and protect the circuit. Different jobs, and you can run both.
## How it works
Both services follow the same daily cycle.
Each day, a balance responsible party (BRP) forecasts how much flexible power your enrolled portfolio will have available tomorrow.
Spirii bids that flexibility into the TSO's market at a price, through the BRP. Spirii cannot sell to a TSO directly, so a BRP partnership is part of the service in every market.
The TSO buys the cheapest bids that meet its need. Several providers compete, which is why a market exists at all.
When the grid needs balancing, the TSO's signal reaches Spirii through the BRP, and charging power across the enrolled portfolio adjusts.
You are paid for the flexibility your portfolio made available.
### FCR-D up
Frequency containment reserve for disturbances is the TSO's first line of defence. When frequency falls below 49.5 Hz, enrolled chargers reduce power within 30 seconds, and that reduction in consumption helps frequency recover.
The "up" means the frequency is pushed up, by consuming less.
FCR-D pays on one component: the **capacity market**, for being available and ready. You are paid whether or not the reserve is called on.
### aFRR
Automatic frequency restoration reserve takes over from FCR-D after roughly 30 seconds, bringing frequency back to 50 Hz rather than merely arresting its fall.
Rather than reacting to what each charger measures, the portfolio keeps headroom in its consumption: a reserve it can move within. The TSO then sends signals every few seconds telling it how much to increase or decrease.
aFRR pays on two components:
* The **capacity market**, for holding that headroom available
* The **energy activation market**, for the energy actually delivered when the TSO calls on it
### Working alongside local energy management
Grid balancing sits directly beneath load balancing in the order things resolve. Load balancing always comes first, because the fuse has to be protected. Grid balancing then reduces power inside that boundary, and whatever is left is what the optimisation capabilities have to work with.
```mermaid theme={null}
flowchart TD
A("Load balancing\nthe circuit's fuse limit") --> B("Grid balancing\nreduces power within that limit")
B --> C("Optimisation capabilities\nwork with what remains")
```
Three properties define how it behaves at a site.
**It only reduces power.** Both services are up-regulation: they help frequency recover by consuming less. Grid balancing never asks a charger for more power than it was already drawing, so it cannot push a circuit toward its limit.
**Power released is not reallocated.** Consider a location with two 75 kW chargers on a circuit fused at 100 kW, load balancing enabled, and both chargers mid-session at 50 kW.
An activation asks charger A to drop to 30 kW. Charger A reduces, and the 20 kW it releases stays unused — load balancing does not pass it to charger B. If it did, the site would consume exactly as much as before and nothing would have been balanced.
**It acts on sessions in progress.** A charger with no vehicle connected has no power to reduce, which is why the available flexibility is forecast daily rather than fixed.
### What drivers experience
Grid balancing is designed to be close to invisible, and for FCR-D it is. Activations trim power by a few percentage points and usually last under ten seconds, frequently a fraction of a second. No driver notices a micro-adjustment on that scale.
aFRR reserves more power and holds it for longer, up to fifteen minutes, so a driver charging through an activation may see their power drop.
Your lever is **hours**. You choose when your portfolio bids, so a network built on overnight home charging can offer flexibility while its drivers are asleep and leave daytime sessions alone.
Adjustments apply to all charging on an enrolled charger, whoever the driver is and whichever app or contract they arrived with.
Charging resumes when an activation ends. Spirii holds safeguards that return enrolled chargers to normal power independently of the balancing signal, so a signal that fails to arrive does not leave a charger throttled.
## Options & configuration
You keep control of how much of your portfolio is exposed, when, and at what price.
| Control | What you set | Why you would change it |
| -------- | ------------------------------------------------------------------ | -------------------------------------------------------------------------------------------- |
| Capacity | Which chargers are enrolled, and what share of the forecast to bid | Start with a subset while you build confidence, then increase it |
| Hours | Bid around the clock, or only in chosen windows | Confine flexibility to periods where a power reduction costs you nothing |
| Price | The compensation you are willing to accept | A lower price wins more bids; a higher one is selected less often but pays better when it is |
Choosing between the two services is mostly a question of portfolio size and driver tolerance:
| | FCR-D up | aFRR |
| ------------- | --------------------------------------- | --------------------------------- |
| Trigger | The charger's own frequency measurement | A TSO setpoint every few seconds |
| Response | Within 30 seconds | Continuous through the activation |
| Duration | Seconds | Up to 15 minutes |
| Paid for | Availability | Availability and delivered energy |
| Driver impact | Not perceptible | Possibly perceptible |
Minimum bid sizes apply, they differ by service and by market, and they determine which services your portfolio can reach at all. Spirii confirms what your portfolio qualifies for during enrolment.
## When to use it
**A large base of home or workplace charging.** Vehicles plugged in overnight for far longer than they need are the ideal resource: there is slack in the session, and a fifteen-minute reduction at 3 am changes nothing for the driver.
**A depot fleet charging between shifts.** The same logic, with the added benefit that you control the vehicles and the schedule, so you know exactly how much slack exists.
## Set up
**Prerequisites**
* **Market.** Grid balancing is available in Denmark, across both the DK1 and DK2 grid zones.
* **Validated hardware.** Enrolment runs on charger models Spirii has validated for grid balancing specifically.
* **Portfolio size.** Minimum bid sizes mean a portfolio has to reach a certain scale before it can participate.
Talk to your account manager to get started.
### Why hardware validation is separate
Grid balancing asks more of a charger than ordinary charging does. A charger has to report metering fast enough for a TSO's timescales, accept dynamic power limits reliably, and hold a session open while delivering zero power without terminating it. Plenty of models on the market cannot do all three, so validation for grid balancing is assessed per model rather than inherited from a charger being supported for charging.
## Dependencies & limitations
* **Denmark only.** The service runs in the DK1 and DK2 grid zones.
* **Validated models only.** A charger model has to pass grid balancing validation before it can be enrolled, which is a higher bar than support for charging alone.
* **A balance responsible party is always involved.** Spirii reaches a TSO through a BRP rather than directly, in every market.
* **aFRR can be perceptible to drivers.** Activations of up to fifteen minutes may show as reduced power. Bidding hours are how you manage that exposure.
* **Enrolment is handled by Spirii.** Chargers are added to and removed from grid balancing on your behalf.
## Related
Load balancing is the boundary grid balancing works inside, so it is worth understanding before you enrol.
Load balancing, price optimised charging, prioritised charging, and programmatic charger control.
The units whose power grid balancing adjusts.
Where local energy settings are configured, and how chargers are grouped.
How the energy delivered during an activation is still recorded and billed.