Brownouts are a fact of Philippine life, and the honest answer to backup sizing is that you cannot afford to run everything. The useful question is which circuits genuinely need to stay alive, and what that costs.
Backup sizing has two separate numbers. Power, in watts, decides whether the inverter can start your loads at all. Energy, in kilowatt-hours, decides how long it lasts. A battery that can run a refrigerator for eight hours may still fail to start an aircon, because those are different limits.
Four hours of backup, by load
| Load | Power | Energy over 4 h | Battery needed |
|---|---|---|---|
| WiFi Modem | 10 W | 0.04 kWh | 1 Ah at 48 V |
| LED Bulb x4 | 36 W | 0.14 kWh | 4 Ah at 48 V |
| Electric Fan x2 | 120 W | 0.48 kWh | 14 Ah at 48 V |
| Refrigerator | 150 W | 0.60 kWh | 17 Ah at 48 V |
| LED TV | 60 W | 0.24 kWh | 7 Ah at 48 V |
| 1HP Aircon | 900 W | 3.60 kWh | 104 Ah at 48 V |
Battery figures allow for inverter losses and an 80 percent depth of discharge, which is what LiFePO4 packs are normally specified to. Never size a battery to its nameplate capacity; you will not get all of it and you will shorten its life trying.
Start-up surge is what kills undersized inverters
Anything with a compressor or a motor draws several times its running wattage for a fraction of a second at start. A refrigerator running at 150 W can pull 450 W starting. A 1HP aircon compressor can pull close to 2,700 W. An inverter that comfortably runs a load may still refuse to start it.
This is why the practical minimum for a household backup covering a fridge, lights, fans and devices is usually a 2,000 W inverter or larger, even though the running load is a few hundred watts. Inverter aircon units are the exception: they ramp rather than slam on, which is why they behave far better on battery than non-inverter units of the same horsepower.
What most households should actually back up
- Modem, router and phone charging. Tiny draw, disproportionate value during an outage. A small UPS handles this alone.
- Lights. LED lighting for a whole house is under 100 W.
- Electric fans. Far more achievable than aircon and enough for comfort in most conditions.
- Refrigerator. Worth including for outages beyond a few hours, purely to protect food.
- Aircon, only if you have sized deliberately for it. It roughly triples the system you need.
Solar with battery, or a generator
A generator is cheaper upfront and unlimited in runtime as long as you keep feeding it fuel. It is noisy, needs maintenance, cannot run indoors, and does nothing for your bill on the 360 days you are not in an outage.
A hybrid solar system with storage costs considerably more, adds roughly ₱60,000 to ₱150,000 over a grid-tied install, and lengthens payback because the battery buys reliability rather than savings. What it does give you is silent automatic backup and a system that works every day rather than only during failures. In areas with frequent, short brownouts the battery wins. For rare, multi-day outages a generator is hard to beat.
Questions people actually ask
[hed_faq]Anong laki ng battery ang kailangan sa brownout?Depende sa kung ano ang gusto mong paganahin. Para sa ilaw, bentilador, modem at ref sa loob ng apat na oras, karaniwang sapat ang 2 hanggang 3 kWh na usable capacity at 2,000 W na inverter.
Can solar panels power my house during a brownout?Not without a battery and a hybrid inverter. Grid-tied systems are required to shut down when the grid fails, so a standard installation gives you nothing during an outage even in full sun.
What size inverter do I need to run a refrigerator?At least 600 W for a typical 150 W refrigerator, because the compressor surges to roughly three times running power on start. Sizing to running watts alone is the most common mistake.
Can I run aircon on a home battery?Yes, but it changes the system substantially. A 1HP unit needs a large inverter for the start surge and consumes more in an hour than lights, fans and a fridge use in several. An inverter-type aircon is far more battery-friendly than a non-inverter one.[/hed_faq]