Shared grid connection could cut payback for Dutch apartment battery

A 70 kWh battery in a 58-apartment building in the Dutch city of Utrecht would pay for itself in about 0.55 years if the apartments’ individual grid connections were folded into the building’s existing facilities connection, according to a new study from Utrecht University.

The researchers said the scenario is notional: they did not assess whether such consolidation is contractually or legally possible.

The 1970s 10-story building was renovated to an energy-positive standard in 2019 and 2020, with 356.6 kWp of roof- and facade-integrated PV, roof-mounted heat pumps, and two iwell PowerCube batteries with a combined 70 kWh and 60 kW of discharge power. About 175 kWp of the PV serves the building’s shared facilities, and 181.6 kWp sits behind individual apartment meters. In 2022 the building consumed 200 MWh and generated 255 MWh.

The researchers modeled battery dispatch on a full year of measured hourly data from 2022, including a cost for battery degradation.

Combining all 58 apartments behind the facilities’ 110.4 kW connection would push summed PV exports past that limit for 122 hours a year, mostly at summer middays. The researchers found the installed battery clears all of those hours, which would let the building drop 58 apartment connections at €350.45 ($393.90) each a year under grid operator Stedin’s tariffs, saving €20,326 annually. In that scenario, after capital and degradation costs, the 70 kWh battery yields a net benefit of €25,297 a year.

The economic optimum lies near 280 kWh, at €32,829 a year and a payback of 1.7 years. Varying battery replacement cost by 50% in either direction moves the optimum between 245 kWh and 350 kWh, and payback at 70 kWh stays under one year.

Peak shaving adds nothing at this site. Optimized dispatch cuts peak grid import to about 56 kW at the installed capacity, but Stedin’s connection tariff is set in capacity brackets, so the reduction earns no savings. The researchers said per-kilowatt capacity pricing would change that.

In the building’s current setup, where the batteries serve only the facilities, there is no peak to shave, and the batteries raise facilities’ PV self-consumption from 37.4% to 53.4%. That is worth a net €4,227 a year, a payback of about 3.3 years, with an optimum near 175 kWh.

The measured data also allowed a comparison with the batteries’ installed control system, which was configured for PV peak shaving. Over 7,895 hours of valid metering, facility self-consumption under the default control was 37.5%, against 37.7% simulated with no battery.

Optimized dispatch of the same 70 kWh reached 52.8%. The researchers said the default control had little to act on because facility flows never approached the connection limit, and that their optimization assumes perfect foresight, so it marks an upper bound for a real-time controller.

The valuation credits no revenue for exported PV, which the researchers said matches the situation once the Netherlands ends net metering on Jan. 1, 2027. The connection saving is not affected by that reform. The study uses hourly data, which the researchers said makes self-consumption figures slightly optimistic, and a single year, 2022, that was above average for solar irradiation in the Netherlands. It combines 2024 Stedin tariffs with 2022 operating data and a 2022 average household electricity price of €0.40/kWh. The work was supported by the TKI Urban Energy Apt-Bat project and the EU Horizon 2020 ARV project.

The building, owned by housing corporation Bo-Ex, was the subject of the earlier Apt-Bat project, which included iwell as a partner. That project’s final report found the building could run on a single 3x80A connection with more battery capacity. It said a June 2024 amendment to the Dutch Energy Act made energy sharing possible, but that apartment buildings still face two barriers: residents must remain free to choose their own supplier, and the tax treatment of energy sharing is unclear.

The Dutch storage market is expanding ahead of the net metering phase-out, with about 5 GWh of new storage forecast across market segments by the end of 2026, according to Dutch New Energy Research. The Dutch regulator, the Netherlands Authority for Consumers and Markets, has advised households to self-consume solar power, since suppliers’ feed-in charges will cut returns once net metering ends. Connection capacity is also constrained at the transmission level, where grid operator TenneT has signed a capacity control contract for a 200 MW/800 MWh battery to relieve congestion.

The Dutch researchers described their findings in “Unlocking flexibility in buildings through batteries: a case study of the Netherlands,” which was recently published in Applied Energy.