The power goes out on a Saturday night. Candles, phone torch, the fridge counting down its hours. And in the middle of the blackout, someone at the table says it: "we really should get solar panels". Everyone nods.
Be careful with that conclusion, because there's a trap inside it. And it's the most expensive trap in the Argentine solar market: we've found it installed in real homes, bought in good faith.
The misunderstanding: "I have panels, so I have power during an outage"
No. A standard grid-connected system, what's called on-grid, shuts down when the power goes out. Even at midday with the sun blazing.
It isn't a flaw in the equipment: it's a mandatory safety function. When the grid goes down, there may be a crew working on the lines. If your system kept feeding energy in, it would be energising a line the utility took out of service precisely so they could work on it. That's why every on-grid inverter in the world disconnects itself on detecting that the grid has failed.
Practical consequence: a system meant "for outages" needs batteries and equipment built for that. If backup is part of your motivation, it's the first thing to raise with whoever quotes you, so the proposal is built around what you're actually after.
With that clear, on to the real question. Batteries make sense in three situations, and they're quite different from each other.
Situation 1: you lose power often, and it costs you
Here the battery is insurance against outages. The system that makes it possible is called hybrid: panels, batteries and an inverter able to disconnect from the failed grid and run your home as an island.
What you have to decide isn't "I want batteries" but two more concrete things:
- What do you want to keep running? The fridge, the freezer, lights, wifi, the gate? The water pump?
- For how long? Do outages in your area last an hour or a whole afternoon?
Those two answers determine the size of the bank, and with it the price. Backing up everything, air conditioning and electric water heater included, needs an enormous bank. Backing up the essentials is far more affordable, and it's usually what people actually need.
We've done installations in areas with frequent outages where the criterion was exactly that: not the whole house, the essentials, for as long as outages in that area last. The client didn't buy total independence. They bought the freezer not defrosting, and having lights and wifi. Which was what actually hurt.
Situation 2: you want to make better use of what you generate
With no outages in the picture, a battery can still play an economic role: storing the midday surplus to use at night, instead of feeding it to the grid at a lower price. If your house sits empty until 8pm, this is the situation that concerns you.
Here the analysis is purely numerical: the battery has a cost and a service life, and the benefit is the difference between what the kWh you buy is worth and what you're paid for the one you feed in. Depending on your night-time consumption and your tariff, it may or may not add up. This is the situation where it's most worth asking for the explicit calculation before deciding.
Situation 3: you have no grid
The countryside, the lodge, the house on the island. Here there's no question: batteries aren't optional, they're the heart of the system. Everything you consume at night lives in them.
It's a world of its own, the off-grid system, with its own logic: every load in the house is analysed, because there's no grid to rescue a miscalculation. We've replaced entire diesel generators with these systems. You can live very well without a grid, but it's designed with far more care.
Your checklist before talking about batteries
- Is your grid stable and your motivation the bill? You probably don't need them today
- Do outages cause you a real, recurring problem? Write down what you want backed up and for how many hours
- Think you might want them later? Say so now: it shapes the choice of inverter
- No grid on your property? Look for specific off-grid experience
- For any quote containing the word "backup": "if the power goes out on a sunny midday, what exactly stays on?"
That last question sums up the whole article. The honest answer may be "nothing, this system is for savings, not outages", and that's perfectly fine if that's what you bought. What can't happen is discovering the answer during the first outage.