Store today's sunshine
Use it tonight

Which of these matters most is different from one household to the next, and it is worth knowing which one is yours before you look at sizes. They do not all point at the same battery.

A rooftop system produces on a curve: nothing before dawn, a peak around midday, nothing after dusk. A house consumes on a different one. A small rise in the morning, less through the middle of the day, and a long evening peak that starts about the time production stops.

Lay the two curves over each other and the overlap is electricity you use as it is generated. Everything under the production curve and outside that overlap goes to the grid. Self-consumption is the name for the share you use yourself, and raising it is what a battery is for.

How large that share is before any battery is added varies a great deal from one property to another. Daytime occupancy, air conditioning, a pool pump, EV charging, the size of the array and the household's total consumption all move it, and so does the season.

Under net billing the electricity your system sends to the grid and the electricity you buy from it are valued differently. Exported units earn the export rate. Imported units cost the full retail price.

Storage works in the space between those two. Electricity that would have gone to the grid can be kept and used by the household later the same day, which turns an exported unit into one you never had to buy.

That is one of the main sources of a battery's value in Cyprus. The table below is the whole idea in three rows.

A bigger battery is not automatically a better battery. What decides the right size is not how many kilowatt-hours the roof makes in a year, but how much of it is spare at the moment it is made and how much of that the household can use after dark.

Annual production alone cannot answer that, which is why this chapter explains what goes into the decision rather than handing you a number. Two houses with the same array and the same annual figure can want very different storage.

A standard grid-connected system shuts down when the grid goes down, battery or not. That is a safety requirement rather than a shortcoming: it stops your system feeding a line somebody may be working on.

Backup is designed in on purpose, and there is more than one way to do it. Some installations carry a set of essential circuits, which is the simplest and least expensive approach. Others can support a much larger part of the home. What is possible depends on the inverter, the battery, the electrical installation, whether the supply is single or three phase, and how much backup power the household wants.

It is worth knowing what happens to the panels too. In a standard system they stop with everything else. In a correctly designed hybrid backup system the solar can, in some configurations, keep supplying the house and charging the battery while the grid is away, which turns a long outage into something a household can live through rather than wait out.

High-power appliances are the part to think about in advance. Air conditioning, an oven or a pump draws heavily and can exceed the backup output of a smaller system, and it will empty a battery faster than lighting and a fridge. Whether a particular appliance can run comes down to the inverter's backup power, the battery's discharge power, the appliance's starting load and what else is on at the time.

If riding out a cut matters to you, say so before anyone quotes. It is a design decision, and it is much easier to build in than to add afterwards.

Plenty of good systems start without a battery, and adding one later is a normal thing to do. The question is what it takes when the time comes, and that is largely settled by the equipment already on the wall.

A hybrid inverter has the battery connection built in, so adding storage later is a battery, a morning of work and a commissioning check. Where the original inverter has no battery connection, storage can still be added through an AC-coupled solution, which puts a second piece of equipment alongside the existing one rather than replacing it. That works well and is slightly less efficient than a system designed for storage from the start, because the electricity is converted an extra time on its way in.

NorthWatt generally specifies hybrid inverters, and future flexibility is one of the reasons we prefer them. A homeowner who adds a battery three years later should not have to redesign the solar system to do it.

It is a fair question to put to any installer, in these words: if I add a battery in three years, what would have to change?

There is one case where storage is specified from the start for a different reason. Where the network will not accept exported electricity, a zero export system holds production back to what the property itself can use, and a battery is what turns the surplus it would otherwise waste into something the house has later.

This is the part worth understanding properly, because it is where quotes differ most. Storing a kilowatt-hour does not earn you the full retail price. That unit would have earned the export rate if you had let it go, so the honest figure is what you avoid paying minus what you gave up receiving.

There is a second thing to account for. A kilowatt-hour put into a battery is not quite a kilowatt-hour taken back out: converting in and out costs a little, and around 90% coming back is a reasonable figure for a modern home battery on a hybrid inverter. The arithmetic below carries both, which is what makes it match a real bill.

The result is a straightforward calculation with nothing hidden in it, and one you can run against any quote you are given.

A grid-connected home stays connected, and that is a good thing: the network is there for the evenings a battery cannot cover and the weeks when production is low. What storage changes is the proportion.

Electricity generated in the afternoon and used at eight in the evening is electricity the household did not buy. Do that most days of the year and a meaningful share of the evening runs on the roof rather than on the network.

That is the everyday version of energy independence, and it is the one that shows up in a bill. Store today's sunshine, and use more of it yourself.

Nobody can tell you what electricity will cost in Cyprus in ten years, and this chapter does not try. What can be said is which part of a bill is exposed to the answer. Electricity you generate and use yourself is priced by an installation you have already bought. Electricity you import is priced by whatever the retail price is that year.

That is why a rising electricity price shortens the payback on solar and storage rather than lengthening it. The value of the system is measured in units of the thing that is getting more expensive.

The same reasoning applies to the export rate, in the other direction. It is set by policy rather than by a market, so a household that keeps more of its own production is less exposed to changes in either number.

There are a great many home batteries on the market and most of them work. The useful question is not which is best in the abstract, but which behaves well on a Cyprus roof, in a Cyprus summer, in a house whose evening starts at seven. That is the part we have already done.

The systems that come through it well share three things a homeowner benefits from later. Capacity that can grow. A battery and inverter designed to work together. Monitoring that makes it obvious when the system is doing its job.

The table below is what we look at, in the order we look at it, with what each line changes for the household rather than what it says on a datasheet. It is here so you can see the reasoning, not so you have to repeat it.