It comes down to how much power you need and how long you need it for (and how much you are prepared to spend). It is possible to make these units work for extended periods, but you need to be frugal with the power you use. Do a backup power audit.
If you have a power inlet and transfer switch already working for a regular generator, then a portable power station supplying the same power standard (voltage and outlet plug configuration) will work fine.
All you need to understand are:
- the power output limitation of your portable power station, which means you'll need to be careful with what appliances you expect to run. This is no different to a regular generator. Try to use too many things as once and it will overload and shut down. Forget about using power hungry appliances like electric heating, clothes dryers, larger aircon units, electric water heaters.
- the energy capacity of the unit and how long you can expect that to last given your expected average power demand during backup period.
- how to charge it
Given the capacity of the portable power stations like Bluetti, from battery alone you can expect to be able to run a handful of low power lights (LEDs), internet router, a (modern) fridge/freezer, keep a phone charged, perhaps a laptop going for say 8-12 hours, but if you expect to use any high power devices then it will drain the battery far more quickly, or it may not be able to supply that much power anyway.
So then it becomes a case of what to do if you think you need either:
- more power
- more energy to last longer
More power simply means a unit or other system capable of supplying that, a larger inverter output. If you do really need more power (even briefly) then these current portable power stations are probably not going to cut it.
More energy means a larger battery (some have battery expansion packs) and/or ways to charge it without grid power. Solar PV is the obvious choice but that may not always be possible / practical in an urban setting. With a Bluetti there's also a limit to how much power solar PV can supply, and the sort of fold out solar power panels you often see coupled with these units are at best going to trickle feed the battery and simply delay the inevitable. In some cases you may find using a regular generator during the day and the Bluetti at night is a viable option.
I have a power inlet and transfer switch for our home and used to use an inverter generator for backup. Worked well and being rural, noise isn't a concern. I've since replaced that with an off-grid battery/inverter/solar PV system, and the generator is there for redundancy. Uses the same power inlet the generator did. In our case that's a 20A / 230V inlet.
I did a backup power audit for our home (I have 3 buildings to cover). I worked out I needed to supply ~5-600W average but with the ability to draw something over 3kW for brief periods. If I expect to need to be able to run for 12 hours then I'll need at least 7.2kWh of useable storage, add 20% for losses, let's call it 8.6kWh. That about 5 times the usable capacity of a Bluetti.
If I need to run for longer then I'll need a way to recharge the battery while also supplying the home = solar PV array, with the generator being redundancy in case solar PV is inadequate. 2 hours of generator charging the battery will gives about another 8 hours of outage backup.
So I ended up with a 4kW all-in-one inverter, 2.2kW of solar PV array on the garage and 18kWh of lead acid battery storage (of which 50% is nominally useable, although more in a pinch if really needed). It plugs into the same power inlet I used for the regular generator and works a treat. It also has grid input/pass through capability with UPS mode so it can seamlessly cut over to battery and back to grid supply during periods of intermittent outages.
