It is designed to backup your most important appliances. You can start with one or have one in each room.

Understood. My boiler/furnace is the single most important "appliance" in my house. I guess I still need an electrician and/or use the traditional gas generator/panel switch approach.

Some furnaces are still 120 volt (same as an outlet) so depending on how the furnace is connected, Pila could be an option or at least could work with some minimal electrical work. But definitely recommend chatting with a good local electrician to pick the right path

If you get an electrician to rewire it to have a plug, you could certainly back it up with Pila.

To add more: To backup big 240V appliances that are hard-wired (EV charger, large HVAC, for example) you need to connect the backup system in the same hard-wired way to the electrical panel. For folks who are keen to make the big investment in whole-home backup, it’s a great solution. Our goal is to give folks more onramps to get started with smart battery backup, focusing on no-rewiring solutions. But I’ll say, Pila can be a compliment to whole home backup systems to add a bit more backup capacity where it matters most

It doesn't need to be hardwired. Devices like the Generlink provide an outlet to plugin in a fossil-fuel based generator or a battery backup unit, and take care of islanding. They sit somewhere between the utility company meter and the main service panel. Power goes out ... plug into the Generlink and if your generator/backup can handle it, your entire system is running again. Not cheap though - around $1k without installation (which can vary from insanely easy to complex, depending on your situation).

Assuming your boiler is 120v, you can have an electrician install a "generator switch" that lets you plug in a generator directly to the boiler; or you can just rewire the boiler to a standard, 3-prong 120v plug.

The bigger issue is how many amps the heating system draws. Assuming it's really a furnace that pumps hot water, (as opposed to a boiler that sends steam to radiators) those pumps really do draw a lot of current.

Get an electrician to put your oil burning boiler on a plug, then you can plug it into whatever source (UPS, generator, UPS with fancy marketing) you want.