Hybrid inverter specification for Cyprus installations

A hybrid inverter is specified by four independent ratings, and a datasheet that leads with only one of them is hiding the other three. The PV input defines how much array can be connected and across how many trackers. The AC output defines what the unit can deliver continuously to the grid connection. The battery port defines how fast stored energy can move in either direction. The backup output defines what happens when the supply fails, and it is almost always the smallest of the four. Sizing a Cyprus installation means fixing all four against a load profile, not picking a headline kilowatt figure that happens to match the array.

The specification in plain terms

PV input. Three numbers govern it: maximum DC input voltage, the number of maximum power point trackers, and the current each tracker accepts. The voltage ceiling is what a string design is checked against, at the coldest expected module temperature, because open-circuit voltage rises as temperature falls. Cyprus is warm, which helps, but inland sites reach genuinely cold winter mornings and a string sized against summer conditions alone can exceed the ceiling at dawn in January.

Tracker count decides how many roof planes are handled independently. A Cypriot flat roof with parapets and a stair enclosure frequently ends up as two or three orientations, each needing its own tracker.

AC output. The continuous output in kW, and separately the apparent power in kVA, which is the figure the connection is assessed against. The ratio between installed DC array and rated AC output — the DC to AC ratio — normally sits around 1.1 to 1.3 on Cyprus roofs. Oversizing the array relative to the inverter is deliberate: it lifts output in the shoulder months and through the morning and evening, at the cost of clipping the peak of a clear June day. Push the ratio much beyond that band and the clipping stops being a rounding error.

Battery port. Two architectures dominate. Low-voltage systems run a 48 V nominal DC bus; high-voltage systems stack modules to a much higher bus voltage. The distinction is not cosmetic. High-voltage stacks move the same energy at lower current, which means smaller conductors and lower resistive losses, and they generally deliver higher continuous discharge power. Low-voltage systems are more forgiving to extend later. What matters at specification stage is that battery and inverter sit on the same architecture, speak a common protocol over CAN or RS485, and appear on each other's published compatibility list. This is the most common source of a commissioning that will not complete.

The port's own ratings — maximum continuous charge and discharge current — determine how quickly a battery absorbs midday surplus and how much load it carries in the evening. A large capacity behind an undersized port delivers its energy slowly, which is a different product from the one most buyers think they have bought.

Backup output. Sometimes labelled EPS. Two questions decide whether it suits the property: what continuous load it supports, and what surge it tolerates. Motor starting is the constraint in Cyprus, because the loads people most want backed up are air conditioning compressors, circulation pumps and borehole pumps, all of which draw a multiple of running current for the first fraction of a second. A backup rating adequate for lighting and a fridge will trip on the first compressor start.

Standards that apply in Cyprus

Grid connection of a generating unit to the low-voltage distribution network in Cyprus is assessed against the European harmonised requirements for generating plants — the EN 50549 series — implemented through the connection conditions the Electricity Authority of Cyprus applies, within the regulatory framework the Cyprus Energy Regulatory Authority sets. In practical terms this means the inverter must hold a grid-code certificate for the applicable profile, must implement loss-of-mains protection so it disconnects when the supply is absent, and must be capable of the voltage and frequency response behaviour the network operator requires.

The country or grid profile setting inside the inverter is a configuration item, not a factory default that can be assumed. An inverter shipped with a profile for another market and left that way will behave incorrectly during a network disturbance, and the setting is invisible unless someone looks for it.

Product safety for the converter falls under the IEC 62109 family, which covers power converters used in PV systems. Battery systems bring their own requirements, with IEC 62619 covering safety for secondary lithium cells in industrial applications. Neither is something a purchaser verifies by reading; the relevant action is to require the declarations of conformity in the handover pack.

Above all of this sits the design signature. Anything involving a connection agreement, an export limitation scheme or a three-phase installation needs a designer registered with ETEK, and the drawings should carry that name.

Common specification errors

Sizing the inverter to the array and ignoring the battery. An inverter selected because its AC rating suits a proposed array can have a battery port that throttles discharge well below the property's evening load. The evening load is why the battery was bought.

Mismatched battery and inverter. Compatibility is per model and per firmware version, not per brand. Two products from the same manufacturer are not automatically a pair.

Backup output sized on average load. Rated continuous power tells nothing about surge. Where an air conditioning compressor or a pump must run on backup, the surge rating and its duration are the figures that matter, and soft starters are frequently the cheaper answer to an inadequate one.

Thermal derating treated as a footnote. Every inverter derates output above a rated ambient temperature. Cyprus summer conditions inside an unventilated garage, a closed plant room or a west-facing external wall in afternoon sun reach temperatures at which derating is continuous rather than occasional. The mounting position is part of the specification. Shaded, ventilated, north-facing where possible, and never directly above the battery.

Coastal corrosion ignored on the enclosure. In Kato Paphos and along the exposed coastal strip, salt-laden air is a design input rather than a nuisance. Marine-grade or galvanised fixings and an adequate ingress protection rating for outdoor mounting are the standard response.

No export limitation where the feeder is constrained. Some connections are approved only with export limited to a set value, which requires a current transformer or meter at the point of supply and a configured limit inside the inverter. Where that is a condition of connection it cannot be added by software alone if the metering hardware was never fitted.

Mounting position chosen without reference to the building. In the 1970s to 1990s apartment stock that dominates areas such as Strovolos, there is often no practical location for a battery within the demised area, and the common parts are not the owner's to use. Resolve this before equipment is ordered.

How to check what was installed

The handover pack is the audit trail, and it should be requested as a condition of final payment rather than asked for later.

1. Nameplate photographs with serial numbers

   Inverter, battery modules and battery management unit, each photographed so the model and serial are legible. These are what a warranty claim is made against and what a future contractor needs to establish compatibility.

2. The commissioning report

   String open-circuit voltages measured at commissioning, insulation resistance, earth continuity, protection settings and the confirmed grid profile. String voltages recorded on day one are the baseline every later fault diagnosis is compared against.

3. Firmware versions, recorded

   Both inverter and battery. Compatibility is version-specific, and an undocumented firmware state makes a later incompatibility difficult to unpick.

4. The single-line diagram, as built

   Showing string arrangement per tracker, DC and AC isolation points, the protective devices and their ratings, the earthing arrangement and the location of any export limitation metering. As built, not as designed.

5. Isolation and protection, verified physically

   A DC isolator that is reachable, labelled and rated for the string voltage; an AC isolator at the inverter; residual current protection of the type the installation calls for. Labelling is not decoration — it is what an electrician or an emergency responder works from.

6. Monitoring access under the owner's account

   The portal account should belong to the property owner, with the installer granted access rather than holding it. This is the item most often left in the installer's name, and it becomes an obstacle at exactly the moment the relationship ends.

Once running, the monitoring data answers the question the specification set out to answer. Compare battery discharge power against the evening load, and check whether the array is clipping for hours or for minutes at midday. Clipping for minutes is the DC to AC ratio working as intended. Clipping for hours means the inverter is undersized for the array that was sold.

For context on what the underlying components cost, installed storage and rooftop PV are priced separately and should be compared separately.

The battery storage section of this site covers chemistry and capacity sizing in more depth, and the district coverage pages record where local grid conditions change the connection route.

Common questions

Should the inverter be sized to the array or to the load?

To the AC connection first, then checked against both. The AC rating is what the connection agreement covers and what the property can draw through it. The array is then sized above it within a DC to AC ratio of roughly 1.1 to 1.3, and the battery port is checked separately against the evening load the storage exists to serve.

Can a hybrid inverter be retrofitted to an existing PV system?

Frequently, though it means replacing the existing inverter rather than adding to it, and the string layout has to be checked against the new unit's voltage ceiling and tracker configuration. Where the original strings were designed around a different topology, rewiring at the array is sometimes required, and that cost belongs in the comparison against an AC-coupled alternative.

What size battery pairs with a given inverter?

Capacity is set by the energy to be shifted overnight; the inverter constrains how fast that energy can move. A battery larger than the port can usefully discharge delivers its stored energy over a longer period, which suits a steady overnight base load and does not suit a household that draws heavily for three hours after sunset.

Does a hybrid inverter keep the property running during an outage?

Only through its backup output, only for the circuits wired to that output, and only within its continuous and surge ratings. A hybrid inverter connected without a backup output and a changeover arrangement disconnects during an outage in the same way any grid-tied inverter does, because loss-of-mains protection requires it to.

Where should the inverter be mounted?

Indoors or under cover, shaded, ventilated, away from direct afternoon sun and not immediately above the battery. On the coast, the enclosure rating and the fixings need to account for salt exposure. A position chosen for cable convenience rather than for temperature is a position that will derate through every Cypriot summer.