The most common complaint we hear isn't "the inverter broke" — it's "the backup doesn't last as long as we thought it would." Almost always, this traces back to sizing: the inverter or battery was chosen for a rough budget, not an actual load calculation.
Step 1: List What Needs Backup
Not everything in your home needs to run during a power cut. Typically this means a few fans, lights, the Wi-Fi router, TV, and maybe a fridge — not air conditioners or heavy motors, which need a much larger (and costlier) setup.
Step 2: Add Up the Load
Each appliance has a wattage rating. A ceiling fan is roughly 75W, an LED tube light 20W, a TV 100–150W, a fridge (compressor cycling) can peak around 150–200W. Add these up for everything you want backed up simultaneously — this total tells us the VA rating of inverter you need.
Step 3: Decide How Long You Need Backup For
This determines battery Ah (ampere-hour) capacity. A home wanting 4–5 hours of backup for a moderate load needs meaningfully more battery capacity than one wanting just 1–2 hours to bridge short outages.
Step 4: Leave Headroom
Sizing exactly to today's load leaves no room for that extra fan or a slightly older, less-efficient appliance drawing more power than rated. We generally recommend 20–25% headroom above your calculated load.
This is exactly the calculation we walk through on every new inverter enquiry — tell us your appliances and desired backup time, and we'll size it correctly the first time, rather than you finding out the hard way during the next outage.
