Reserved power: what it is and how to set it for solar PV and battery storage

28 October 2026 · 5 min read

Reserved power decides how much your plant or storage may feed into the grid – and how much you pay for the connection. Asking for “more, just in case” does not pay, and neither does too little.

Two terms that get confused

A Czech grid connection contract sets two values. Reserved capacity (rezervovaný příkon) is the power you may draw from the grid – it applies to every point of consumption, from a family house to a factory site. Reserved power (rezervovaný výkon) is the power your generating installation – PV, battery storage, cogeneration – may feed into the grid at the point of delivery. Both values are set by the grid operator in its statement on the connection application and confirmed by the contract; they determine how strong the grid at the site must be and therefore whether, and on what conditions, the connection is approved.

Reserved power is not the same as the installed power of the plant. The panels may have 300 kWp and the inverters 250 kW, yet only 100 kW may leave for the grid – the rest is consumed on site or curtailed by the control system. The grid operator assesses what will actually flow into the grid.

How the grid operator allocates reserved power

Grid capacity is allocated in the order of complete applications. In its statement the operator either confirms the requested power, reduces it, makes it conditional on grid reinforcement, requires connection at a higher voltage level (your own transformer station), or limits the export – for example to zero. Nobody can find out this answer in advance; the operators' indicative maps are only a guide. That is why we submit the application at the very start of the project and finish the design only once the statement is in. The whole process is described on the grid connection page.

Why not ask for “more, just in case”

Share of costs – for a connection or an increase, the applicant pays a share of the grid operator's eligible costs, which for larger capacities is calculated per kilowatt. Every extra kilowatt therefore costs money at the time of connection.
Deposit – for larger generating installations the operator requires a deposit intended to filter out speculative applications.
Unused reservation – power you do not use by the agreed date may be reduced or cancelled by the operator after some time, and the capacity returns to the grid for other applicants.
Monthly charges – for consumption at medium voltage the customer pays the operator for the contracted power (reserved capacity, after the tariff reform the reserved capacity in kW) and for exceeding it. Too high a reservation costs money every month; too low means penalties for exceeding it.

The opposite mistake is just as expensive: if you underestimate the power and later need more, you file a new application and stand at the end of the queue again.

How to set reserved power

Solar PV

We start from how much electricity the site consumes while the plant generates and how much it makes sense to export at current feed-in prices. This gives the inverter power and the requested export; if the operator limits the export, the control system and possibly storage handle the rest. For a family house and smaller businesses the inverter power and the main circuit breaker are usually decisive.

Battery storage

Storage applies for both: reserved power for feeding into the grid and reserved capacity for charging from it. The values follow from the purpose – peak shaving needs a different power than market trading or storing PV surpluses – and from a study of the 15-minute load profile for a whole year. More in the article on commercial battery storage.

Site, hall, charging station

The reserved capacity for consumption is set from the 15-minute maxima over a year and from plans: new technology, heat pumps, EV charging. A correctly set reserved capacity is often a quicker saving for medium-voltage customers than any new technology – and it can be calculated from the invoices.

Reserved power and voltage level

The requested power also decides where you connect. Smaller capacities go to low voltage, into the existing switchboard or service cabinet. From hundreds of kilowatts the grid operator usually requires a medium-voltage connection – which means your own transformer station, an MV feeder, MV switchgear with the operator's metering, and considerably higher costs and a longer preparation. The threshold is not fixed; it depends on the state of the grid at the site. In the site check we estimate the probable voltage level from the nearest lines and transformer stations, but only the statement sets it bindingly. If the project comes out just above the threshold, it is usually worth comparing a lower-power LV variant with the transformer station variant – the difference in investment can decide the whole project.

What goes into the application

a site plan with the connection point and a single-line diagram,
data on the technology: inverter or converter power, storage capacity, the method of export limitation,
the requested reserved power and capacity with justification from the study,
the landowner's consent and the applicant's details.

A complete application keeps its place in the queue; a returned one loses it. After the statement we incorporate the operator's conditions – disconnection point, grid protection, metering, communication – into the documentation so that the installation passes commissioning.

Frequently asked questions

Is reserved power the same as the plant's installed power?

No. Installed power is the sum of the panel or inverter power; reserved power is what may leave for the grid. It can be considerably lower – the control system limits the export.

Can I increase the reserved power later?

Yes, with a new connection application. It is assessed again according to the state of the grid and the queue at that time, so an increase is not guaranteed. It is better to apply from the start for the power that matches the project including its planned expansion.

What if the operator grants less than we wanted?

We propose an adjustment: limiting the export, using surpluses in storage, a different connection point or a medium-voltage connection. Most reductions can be dealt with – just differently from the original plan.

How long does the reservation last?

The connection contract sets a date by which the plant or consumption must be connected. If the date is missed and no change is agreed, the operator may reduce or cancel the reservation – so we track the deadlines together with the permit and construction.

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