Backup power for a villa: battery, generator and UPS for high-end systems

Does a private house need a generator or a battery?

For most coastal villas a battery plus a UPS on the most sensitive systems is enough; a generator earns its place where outages are long, the house is remote, or heavy loads must keep running. A battery switches over without a gap and in silence, but it is sized for hours. A generator runs as long as there is fuel, at the cost of noise and the need for space for exhaust and fuel storage.

The decision does not start with equipment but with a question: what in the house cannot go without power for a day. In a high-end home that is usually the alarm and cameras, the network and router with a backup link, the home control system, the pumps (water supply, drainage, basement sump), fridges and the wine cellar, gates and garage doors, and path and entrance lighting. Air conditioning, the induction hob, the dryer and the pool stay off that list: they draw several times more than everything else combined.

What can you connect to a home battery?

What you connect to the battery is a separate critical-loads panel, not the whole house. The electrical design includes a second board or section holding the circuits that must stay alive in an outage, and the inverter feeds only those. It is cheaper and more reliable than trying to carry the entire house on a battery.

A worked example with assumptions. Alarm and cameras 0.1 kW, network and automation 0.1 kW, fridges and wine cellar 0.3 kW on average, pumps 0.3 kW on average: about 0.8 kW in total, or roughly 19 kWh a day. Home batteries typically hold 5-15 kWh, so 10-15 kWh covers 12-18 hours with headroom for peaks. For a day or more you need solar recharging or a generator.

Look separately at peak power. A 0.75 kW pump draws several times its rating when it starts, and the inverter has to ride out that surge. If a quote lists only capacity in kWh and not the inverter's peak output, ask before you sign.

What to choose: battery, generator or UPS?

The choice depends on how long the outage lasts and on what cannot be interrupted even for a fraction of a second. The comparison, in essence. Battery with a hybrid inverter: switches in fractions of a second, silent, works with solar panels, but is limited in capacity and peak power. Generator: feeds heavy loads for as long as you like, but starts with a delay of tens of seconds, makes noise, needs fuel, ventilation and an exhaust, and has to be test-run and serviced regularly. UPS: holds for minutes, smooths surges and dips, and is needed for servers, network gear, smart-home controllers and the alarm.

In high-end homes the usual answer is a combination. A UPS on the network and controllers so the control system does not reboot; a battery on the critical circuits; a generator where outages run long or there are loads the battery cannot carry. A generator is connected through an automatic transfer switch with an interlock, so it can never feed current back into the grid. The electrician designs and builds that at the project stage; it is not a lead into a socket.

A generator beside the living area makes noise, and your neighbours will tell you so. Choose a sound-attenuated enclosure, a location away from bedroom windows, and check the acoustic rules of your zone.

How do you connect a battery to solar panels?

Through a hybrid inverter or a battery with a separate backup output. This is what people confuse most. A standard grid-tied inverter shuts down when the grid disappears, for safety reasons, and the panels give nothing even in full sun. For the house to stay live in an outage you need an inverter with a backup function (a backup/EPS output) and a separate panel of critical circuits.

There are two layouts. A hybrid inverter brings panels, battery and grid together in one unit; it suits a new installation. A battery coupled on the AC side to an existing inverter suits a house that already has panels, but whether it provides backup in an outage depends on the model; get that in writing.

Under Real Decreto 244/2019, storage can be added to self-consumption installations if it meets the applicable safety requirements, and the storage shares the metering equipment with the installation. Generating sets that run only during grid interruptions fall outside that decree, but the electrical side is still registered by the installer. Panel paperwork is covered in our guide on self-consumption procedures, and choosing size and location in our guide to solar panels for your house.

Do generators and batteries need permits?

The electrical side is always registered by an authorised installer with an installation certificate; the rest depends on the location and the type of equipment, and is checked with the ayuntamiento. For a generator there are three questions: where it stands, how exhaust is vented and fuel stored, and whether the noise meets acoustic limits. In Catalonia noise is regulated by Llei 16/2002 and its regulation, and the actual limits per zone come from the municipal acoustic capacity map and the local ordinance. Check them before buying, not after a neighbour complains.

For a lithium battery, follow the manufacturer's instructions: permitted temperature range, ventilation, clearance from doors and bedrooms, and no installation in damp locations. Do not put it in a basement without drainage or in a closed niche. Tell your insurer; it may ask for the equipment's certificates.

If the house is in the protected coastal strip, also check where outdoor units can go; our guide on the Ley de Costas helps.

Which mistakes come up most often?

People buy a battery without a backup output and find out at the first outage. They choose capacity and forget peak power. They connect a generator with a lead into a socket, with no interlock. They skip the separate critical-loads panel and the inverter tries to carry the whole house. They do not test: switchover is checked once at handover and then not run for five years.

For a non-resident owner there is one more rule: backup power is useless if you do not know it has kicked in. You need alerts to your phone for loss of mains and battery level, and a communications channel that itself runs on backup (router on a UPS, a mobile modem). Once a year run an outage test: open the main incoming breaker, see what switches, how long the battery lasts and whether the generator starts. Write the result down.

How does BCN YARD plan backup power?

Backup power is simplest and cheapest to settle in the electrical design, while walls and routes are open: a separate critical-loads panel, space for the inverter and battery, ducts for a generator and for alerts. We run projects in Russian and Spanish with one person responsible for the site, and the electrics are done by a vetted authorised installer. We draw up the list of critical loads with you after the site visit, size the equipment with the installer and fix the price in the quote.

If the villa is already finished, we start with a visit: we look at the panel, the space for equipment and the list of systems you cannot afford to lose. Write to us and we reply within an hour.