Solar parks and the frequency markets: the money is in capacity

A common assumption is that an asset earns on the frequency markets only when the grid actually calls for energy. For a solar park the reality is different: the bulk of the revenue comes from the capacity market — payment for standing ready to change output, whether or not it is activated within the hour.

And you do not need a battery for that. A solar park qualifies for the capacity market on its own, because it can curtail its output on command — providing downward reserve to the grid. It is paid for being available, not for how much energy is actually moved.

That is what makes the revenue attractive. The capacity fee is paid for every hour the park is available; activations may be few, but the income stays predictable and stable — more like a standing payment for being at the grid's disposal than an unpredictable trading profit.

A battery is not required, but it expands the options: it adds upward reserve and lets the park earn even on a dark winter evening when the panels produce nothing. Many parks add one over time to become a hybrid and cover more markets — but you can start without.

Capacity is bought on several frequency markets — FCR, aFRR and mFRR —, each with its own requirements and prices. Reaching the market alone is hard: it requires Elering prequalification and at least 1 MW. Volton pools parks into one reserve group, handles qualification and submits the capacity bids on your behalf — you never have to become a balance service provider (BSP) yourself.

The result: the park is no longer just a generator — an existing grid connection starts earning steady capacity revenue year-round, and the park becomes an active part of balancing the power system.