From activation test to forecasting grid needs: How two Finnish DSOs tested household EV flexibility to prepare for electrification growth

About the DSOs

KSS Verkko is a regional electricity distribution system operator serving over 50,000 customers in Kouvola and Iitti. Part of the KSS Energia Group, the company actively maintains and develops the local grid infrastructure while exploring new tools to future-proof its operations.

Imatran Seudun Sähkönsiirto (ISSOY) is a distribution system operator in the Imatra region of southeastern Finland. Like many regional DSOs across Europe, ISSOY is preparing for the structural changes that household electrification is bringing to local grid operations.

Both DSOs partnered with Synergi to run household demand response pilots from summer 2025 to spring 2026. The pilots were approved, thanks to Synergi’s compliance with grid regulations and energy authority schemes, such as the Finnish Energy Authority's flexibility incentive for the 2024–2027 regulatory period. The shared goal: to understand how residential EV flexibility can support local grid operations as electrification accelerates.

The challenge: EV adoption is creating new local peak demand

Across Europe, electric mobility is rapidly becoming a major driver of electricity demand growth. While EVs are central to the clean energy transition, they also add substantial load to distribution networks, particularly through home charging.

As home EV charging popularity grows, it creates high demand peaks for local distribution grids. For those on fixed contracts, most households plug their cars in after they arrive home and increase the already high demand peak by charging their cars. In addition, in some areas where dynamic or hybrid contracts are popular, price optimisation creates problems too: if all EVs behind one transformer optimise for the cheapest hour, congestion can appear for those hours as well.

For KSS Verkko, the reality is stark: the company's transmission capacity needs are expected to nearly double by 2033. For ISSOY, the same structural trend is at play. Both DSOs recognised that traditional grid reinforcement alone would not be sufficient, or cost-efficient, to address the growing variability introduced by household electrification.

The question both companies set out to answer was practical: can household demand response, particularly through EV smart charging, serve as a cost-efficient complement to grid investment? And if so, how do you actually build a local flexibility portfolio from scratch?

The solution: Synergi's VPP platform for local DSO flexibility

Synergi provided both DSOs with its virtual power plant (VPP) platform, which unifies household energy assets into a single controllable portfolio. The platform connects to EVs, heat pumps, and solar systems through cloud-to-cloud integrations, with no additional hardware required.

Households within the KSS Verkko and ISSOY grid areas could connected their remote-controllable devices to the free Synergi mobile app. In return, participants received a financial reward for joining and participating in the pilot.

Both pilots followed a structured approach across four phases:

1. Project kick-off and planning: Synergi and each DSO defined objectives, KPIs, and communication strategies.
2. Household recruitment and onboarding: Multi-channel campaigns including press releases, newsletter features, social media advertising, and targeted direct mail to EV owners in specific postal code areas, all driven by Synergi playbook, creating minimum added workload for DSOs.
3. Flexibility testing: A series of up-regulation (start charging) and down-regulation (stop charging) tests, first on pre-scheduled days and later in dynamic two-week windows that better simulated real-world conditions.
4. Analysis and reporting: Joint analysis of results, learnings, and next steps for scaling.

The approach was designed to be as frictionless as possible for households. Joining the pilot took under two minutes through the Synergi app, and participants did not need to take any action during flexibility tests. The system operated on a "set and forget" model, where Synergi's activation signals controlled the charging automatically. In the next section there’s more details about the experiences of households.

The results

Accurate, fast flexibility activation

With over 150 EVs connected across both pilot areas, Synergi conducted a series of up-regulation (start charging) and down-regulation (pause charging) flexibility tests to validate the accuracy and response speed of its VPP activation engine.

The results confirmed that Synergi's platform can hit activation targets with precision. In a down-regulation test, charging was paused across the portfolio in just one minute, a response time fast enough to support real-time grid balancing scenarios.

The pilots also revealed an important insight about activation methodology. Pre-scheduled test days produced less reliable results because spot-price-optimised smart charging had already shifted EV loads before the planned activation window. When the teams switched to dynamic, opportunity-based activation, the accuracy improved significantly. This approach better reflects real-world DSO operations, where flexibility is needed in response to actual grid conditions, not on a fixed schedule.

A proven engagement model for household flexibility

One of the most valuable outcomes of both pilots was the validation of Synergi's end-user engagement approach. Several key learnings emerged:

Simplicity drives retention. The combination of simple onboarding (under 2 minutes via the Synergi app), clear financial incentives, and a fully automated "set and forget" experience resulted in 100% participant retention across both pilots. Not a single household asked to leave either pilot during the testing period.

Flexibility becomes routine. When the second scheduled test day fell on a day with unusually low spot prices, the EVs had already charged automatically through Synergi's smart charging. Rather than being a failure, this demonstrated that participants had fully integrated smart charging into their daily routines, which itself provides a foundation for ongoing flexibility.

What participants said: willing, engaged, and ready to continue

After the pilots concluded, Synergi conducted a participant survey across both DSO areas. The responses paint a clear picture: households are not only willing to participate in grid flexibility programs, they actively want to.

Motivation goes well beyond compensation: When asked about their primary reason for joining, supporting the local grid was the top driver (37%), closely followed by financial benefits from energy optimisation (30%), and interest in new technology (20%). Only 10% cited the pilot compensation as their main driver. This is a strong signal for DSOs: consumers see real value in flexibility participation, not just a one-time payout.

Communication and onboarding worked seamlessly: 100% of respondents rated the pilot communication as clear (60% "very clear", 40% "fairly clear"), with zero respondents reporting confusion. Synergi managed the end-to-end communication process on behalf of both DSOs, based on Synergi’s playbook.

Zero disruption to daily life. 72% of participants reported that smart charging had no impact whatsoever on their daily routines, while the remaining 28% experienced only minimal impact. Not a single participant reported a negative experience. This confirms that automated demand response can operate entirely in the background, which is a prerequisite for scaling flexibility programs to thousands of households.

The app experience was intuitive. 83% of respondents found the Synergi app intuitive to use. The combination of simple device connection, clear reward structure, and fully automated optimisation meant that participants could join and benefit without needing technical knowledge.

Trust in the DSO partnership was high. 70% of participants felt the collaboration between their DSO and Synergi was natural, while 20% were neutral. Zero respondents reported distrust towards a third-party operator. This is particularly relevant for DSOs considering third-party flexibility providers: the partnership model works when the consumer experience is managed well.

90% want to continue using the service. 73% of participants said they were very likely to continue using Synergi after the pilot, with an additional 17% saying they were fairly likely. This retention signal is critical because it means DSOs can build on pilot portfolios rather than starting from scratch each time. The appetite for ongoing participation is there, and it points directly toward the viability of scaling these programs for continuous grid flexibility.

What this means for DSOs

These pilots demonstrate that residential flexibility is a practical and cost-efficient tool that DSOs can deploy today. As EV adoption and solar installations continue to grow across Europe, the available flexibility capacity scales directly with them.

For distribution system operators evaluating their options, the results offer three clear takeaways:

Demand response technology is accurate and fast: Synergi's VPP hit its activation targets in minutes through cloud-to-cloud device control with no hardware required. The precision of the activations confirms that household flexibility can meet the performance requirements of real-time grid operations.

Consumer engagement is solvable: The biggest barrier to DSO flexibility is often assumed to be consumer willingness. These pilots prove that with the right incentives, simple onboarding, and a fully automated experience, households are enthusiastic participants. 100% retention across both pilots makes that case convincingly.

The regulatory environment supports action now: Both pilots were approved under the Finnish Energy Authority's flexibility incentive for the 2024 to 2027 regulatory period. This incentive allocates 1% of a DSO's grid operations revenue specifically for developing and experimenting with market-based flexibility solutions. In the next regulatory period (2028 to 2031), the incentive doubles to 2% of revenue, shifting focus from experimentation to deploying flexibility solutions as part of ongoing grid operations. Finnish DSOs have a clear regulatory runway to move from pilots to operational flexibility procurement.

Beyond EVs: a platform for full household and DER flexibility

While these pilots focused primarily on EV charging flexibility, Synergi's platform is not limited to electric vehicles. The same cloud-to-cloud control architecture extends to heat pumps, and solar PV systems, giving DSOs the ability to manage a wider range of distributed energy resources through a single platform.

For DSOs in Central Europe, where residential and commercial solar penetration is significantly higher, this opens up an additional and increasingly critical use case: automated solar PV curtailment. Synergi's platform can remotely curtail residential and commercial solar inverters when local grid conditions require it, without any on-site hardware or relay installations. This capability is already live through Synergi's PV Manager, which provides cloud-to-cloud inverter control for remote curtailment and ramp-up via API. In markets like the Netherlands, where net metering is being phased out and feed-in volumes are growing, automated curtailment is becoming a necessity rather than an option.

In emergency or peak scenarios, the platform also supports full load shedding across all connected smart devices in a targeted grid area. This gives DSOs a cloud-based alternative to traditional relay-based load disconnection, with the precision to target specific grid segments and the speed to respond within minutes.

What comes next: from activation tests to grid forecasting modeling

The next phase of Synergi's collaboration with DSOs moves beyond activation testing toward something with even greater long-term value for grid planning: aiming to integrate real-time household consumption and solar production data into DSO forecasting models and better understand where grid infrastructure investments can be deferred based on flexibility availability.

Today, most DSOs plan grid investments based on historical load data and broad growth assumptions. As household electrification accelerates, the gap between forecasted and actual local demand is widening. By feeding real-time data from connected households, including EV charging patterns, heat pump usage, and solar production, directly into grid planning tools, DSOs can build significantly more accurate demand models at the substation level.

Synergi is developing an API-based data service that provides DSOs with real-time portfolio availability forecasts, mapped against grid topology. The goal is to enable both short-term operational forecasting (days to weeks ahead) and long-term investment planning (10 to 15 year horizons), allowing DSOs to simulate the impact of growing electrification on specific grid areas and assess where flexibility can defer or reduce the need for infrastructure reinforcement.

In some of the countries, there is also an emerging opportunity around low-voltage grid monitoring. Most DSOs today have limited visibility into what is happening at the low-voltage level of their networks. Connected household devices, such as EV chargers, inverters, and smart meters, can act as distributed sensors that report real-time data on local grid conditions, including voltage levels and frequency. This gives DSOs a cost-effective way to monitor the parts of the network that are hardest and most expensive to instrument with dedicated equipment, and where the impact of electrification is felt first.

Both capabilities point toward a future where distributed energy assets and flexibility are not only tools for managing peak loads, but also as s source of continuous grid resilience that improves investment planning, enhances operational visibility, and ultimately reduces costs for both DSOs and end consumers who fund grid infrastructure through their electricity bills.

Building local flexibility programs that deliver results

At Synergi, we help distribution system operators transform residential flexibility from an abstract concept into a practical grid management tool. Our platform connects household energy assets through cloud-to-cloud integrations, provides automated demand response capabilities, and includes a proven end-user engagement playbook that has achieved 100% retention across multiple DSO pilots.

If you'd like to explore how Synergi can help your DSO leverage household flexibility for local grid operations, get in touch with our team.