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Building the Flanders Capacity Tariff into Your ROI Advice

An investment in solar panels, a battery, or a heat pump changes not just a client's total usage, but also their peak power draw — and therefore their Flanders capacity tariff. A final recommendation that skips that calculates with an incomplete cost picture.

Why kWh Savings Alone Don't Tell the Whole ROI Story

Solar panels mainly lower total usage, but a battery or a shifted charging moment for an EV charger can also lower a client's peak power draw — or raise it, if a heat pump gets added without smart control. Each of these effects feeds through into the Flanders capacity tariff, independent of the savings on regular usage.

This page describes Flanders' capacity tariff, which bills households on their measured quarter-hourly peak power (kW), calculated by Fluvius under VREG rules. This mechanism doesn't exist for ordinary households in Wallonia or Brussels. In Wallonia, you pay a time-of-use tariff (mono-hourly, bi-hourly, or from 2026 the Impact tariff) — Wallonia does have its own "capacity tariff," but it only applies to solar-panel owners (prosumers) and is based on inverter power, not your measured peak usage. In Brussels (Sibelga), network costs are tied to your connection power, not a measured peak.

Solar, Battery, Heat Pump: Different Effects on Peak Power Draw

A payback period that only looks at kWh savings can make an investment look more or less favourable than it really is — depending on whether the client's capacity tariff drops or rises alongside it. For a client with a pronounced peak profile, that effect can be the difference between investing or not.

"Solar Only" vs "Solar Plus Battery": The Capacity Tariff Tie-Breaker

Every generated financial recommendation shows the capacity tariff (in euros per kW, per year) as an explicit line item in the calculation — not a hidden assumption, but a visible part of the figures a client sees. For a client torn between "solar only" and "solar with battery," the effect on the capacity tariff is often the deciding argument — a battery that flattens peaks does so for the grid connection too, not just for their own usage.