The instinct is to size a system based on average usage and whatever cost feels manageable but the better question is what you are actually trying to protect. Are you aiming for whole home backup or just critical loads?
If it is only critical loads, things like the refrigerator, a few lights, phone charging, your router and maybe a medical device, you can cover that with a much smaller system. In many cases, that setup can actually give you longer usable backup time than someone who went for whole home coverage but ended up stretching their budget too thin on a smaller battery.
The best way to approach it is to write down your critical loads in watts then estimate how many hours you need them to run. Once you have that, you can work backward and size the system properly instead of guessing.
At its core, it comes down to a simple calculation. Total watt hours divided by your critical load wattage gives you runtime. When you see it laid out on paper, most people are surprised at how achievable it actually is.
If it is only critical loads, things like the refrigerator, a few lights, phone charging, your router and maybe a medical device, you can cover that with a much smaller system. In many cases, that setup can actually give you longer usable backup time than someone who went for whole home coverage but ended up stretching their budget too thin on a smaller battery.
The best way to approach it is to write down your critical loads in watts then estimate how many hours you need them to run. Once you have that, you can work backward and size the system properly instead of guessing.
At its core, it comes down to a simple calculation. Total watt hours divided by your critical load wattage gives you runtime. When you see it laid out on paper, most people are surprised at how achievable it actually is.
