Is the connection limit the same as the contracted capacity?

Not always. The physical connection (the cable, transformer and protection) sets the hard limit; the contracted transport capacity is what the site has agreed to use and pays for. Size against whichever the grid operator enforces, and ask the client which one it is.

Can 15-minute data prove the site stays under the limit?

It shows 15-minute averages. Protection devices react to much shorter peaks, so the battery's controller must act in real time, with headroom. Zorowatt does not design electrical protection; the installer and the grid operator do.

What if no battery size holds the limit?

Then the problem is energy, not power: the site does not have enough room under the limit to recharge. Shifting the new load (for example slower EV charging) or a flexible grid contract may help more than a bigger battery.

Is this a good investment?

That depends on what the growth is worth to the business and on the alternative — waiting, an upgrade quote, moving the load. A study can give the cost per kW enabled and the payback; the decision is the client's, and it is not investment advice.

Sizing for a connection limit: the smallest battery that keeps you under the kW you have

Why this is the Dutch case

At the end of June 2026 the Dutch regional grid operators' waiting lists held 15,498 requests for more offtake capacity (9,986 MW) and 8,558 for feed-in (5,693 MW) (Solar Magazine, 6 Oct 2026). A 2025 market study for Energy Storage NL put the number of companies on a waiting list above 20,000 in 2024 (ESNL / Ecorys). Liander's tariff sheet states that an increase in contracted capacity cannot be granted where the grid lacks capacity (Liander 2026).

For a site in that position, the question is not how much a battery saves but whether it lets the site grow at all — which is why Zorowatt uses a connection-limit mode by default for Dutch sites.

Step 1: build the future load

Take 12 months of 15-minute data and add the planned load where it will run: EV chargers in the hours the vehicles are home, a heat pump in the winter mornings, a production line in its shifts. The result is the profile the battery has to hold under the limit.

Step 2: power = the largest excess

The largest 15-minute value above the limit is the minimum discharge power. Leave headroom: the limit is physical, and a 15-minute average below it can still hide shorter peaks above it.

Step 3: energy = the longest stretch of excess

Add up the energy above the limit for each continuous stretch, and take the largest. Divide by the discharge efficiency.

Worked example — illustrative, not a real customer: an office of 6,000 m² in Amsterdam with a heat pump and 10 EV chargers, a 150 kW contract and winter-morning peaks of 210 kW (assumptions). The excess is about 60 kW for about 3 hours: 60 × 3 = 180 kWh. At 95% discharge efficiency: 180 ÷ 0.95 ≈ 189 kWh usable at least. A 100 kW / 250 kWh battery covers that with about a third to spare (250 ÷ 189 ≈ 1.32).

Step 4: check the room to recharge

Charging must also stay under the limit, so the battery can only refill in the room between the site's load and the limit. To deliver 180 kWh at 90% round trip it must draw 180 ÷ 0.9 = 200 kWh.

If the office draws 90 kW at night (assumption) under its 150 kW limit, 60 kW is free: 200 ÷ 60 ≈ 3.3 hours to refill. Easy.
If the site runs 140 kW around the clock, only 10 kW is free: 200 ÷ 10 = 20 hours. The battery would not be full by the next morning, and a bigger battery would not help — the limit, not the battery, is the constraint.

Step 5: run the whole year

Test the size through every quarter-hour of the year and count the breaches: quarter-hours above the limit and the energy over it. Zorowatt sets the power to the largest excess and searches for the smallest energy that gives zero breaches. If no size holds the limit, the new load needs more energy than can be recharged under the limit, and the report says so instead of proposing a battery.

Step 6: value it against the alternative

Bill savings are often small. In the office example, holding the kW max at 150 instead of 210 is worth 60 × €3.57 × 12 = €2,570 a year, and the contract increase it avoids 60 × €2.29 × 12 = €1,649 — if that increase was even available (Liander 2026 rates). The decision metric is the cost per kW of growth enabled, compared with waiting for the grid or paying for an upgrade.

Illustrative: a 500 kWh battery at €400 per kWh installed (assumption) costs €200,000; if it enables 100 kW of new load, that is €2,000 per kW of growth.
Real case (vendor source): Oomen Warehousing in the Netherlands avoided a new substation that would have taken about two years (Tesvolt warehousing case).
Real case (vendor source): a battery at Stagecoach's Guildford bus depot in the UK avoided a grid upgrade estimated at £2–3 million and more than 12 months (Zenobē).

Sites that did this

De Walvis office, Amsterdam: 320 kWh battery, 137 kW connection against peaks of about 200 kW, installed to avoid disconnection (Solar Magazine, 27 Apr 2024).
Albert Heijn distribution centre, Zaandam: more than 1.8 MWh / 800 kW for 70 electric trucks and 17 DC chargers after the contracted capacity was reached (vendor: Intercel).
Van Ommen, Beekbergen: a battery and energy management let a metalworking firm add a production hall on a full connection (vendor: Hollander Techniek).

What changes from 2028

The ACM's draft decision of 8 October 2026 would make the Dutch kWmax charge time-weighted from 1 January 2028 (ACM draft). It is a draft. It changes the price of a kW in each hour, not the physical limit of the connection — a battery sized to hold the limit still has to hold it in every quarter-hour.

Check the data first with the free meter data checker, then run the Workspace in connection-limit mode: add the new load, set the limit and it finds the smallest battery that holds it, valued against the upgrade cost you enter.

Frequently asked questions

Is the connection limit the same as the contracted capacity?: Not always. The physical connection (the cable, transformer and protection) sets the hard limit; the contracted transport capacity is what the site has agreed to use and pays for. Size against whichever the grid operator enforces, and ask the client which one it is.
Can 15-minute data prove the site stays under the limit?: It shows 15-minute averages. Protection devices react to much shorter peaks, so the battery's controller must act in real time, with headroom. Zorowatt does not design electrical protection; the installer and the grid operator do.
What if no battery size holds the limit?: Then the problem is energy, not power: the site does not have enough room under the limit to recharge. Shifting the new load (for example slower EV charging) or a flexible grid contract may help more than a bigger battery.
Is this a good investment?: That depends on what the growth is worth to the business and on the alternative — waiting, an upgrade quote, moving the load. A study can give the cost per kW enabled and the payback; the decision is the client's, and it is not investment advice.

Related guides

Sources

Last checked: 2026-10-30. Every figure in this guide comes from the source linked next to it, with the retrieval date Zorowatt's research recorded (28–30 October 2026), or from arithmetic shown step by step.

Stuck on something else? Ask the community.

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