Home Backup Systems, Part One

When I bought my first custom PC back in 1999, a Gateway machine with dual Pentiums (Only PC I ever had which actually did two things at once), one of the things missing living in the Swiss countryside was a reliable power supply. At the time (Uninterruptible Power Supplies) UPS’s were not cheap and the cost of the PC didn’t leave much in the account, so a ‘spike’ protection plug was it. And it must have done the job because despite power outages galore nothing ever went wrong with it. I did however get to sit in the dark on a frequent basis.

Back in the UK I’m still sitting in the dark on a regular basis but have been using a small powerbank to run a couple of LED angle poise lamps, which are much better than the battery powered LED camping lights I had been using. Still, it’s pretty boring if the power cut lasts any length of time.

Add to the above the lunacy of Net Zero, ever increasing electricity prices and grid unreliability the prepper in me decided to bite the bullet in January when I saw the Bluetti AC300 + B300K Home Battery Backup system on sale for £1,199, about half list price though it’s always on sale. A chunk of money but at that price I decided it would pay for itself, probably. Currently best price I’ve seen is £1,499 for the AC300 + B300K and £999 for the batteries, which I hope to see come down in the future. Plenty of other reputable manufacturers, EcoFlow, Anker, Jackery etc. It all depends on what you want to do with it and the price/performance for value and I think the price/performance and functionality of this Bluetti model is pretty good.

What does it do?

Fundamentally it’s just a large powerbank, that thing you take with you to charge your phone etc when you go camping or anywhere you won’t have access to the mains. The main difference being that a home backup system has many ways to charge its battery pack, and different outputs to run/charge different devices ie 6 x 13 amp sockets to plug your electricals into.

Bluetti separate the solar charge controller, AC charge controller, AC inverter (AC300) from the lithium battery and battery management system (B300K modules). This improves redundancy but does increase the overall footprint, I’ve read that the AC300 is so large because of the heatsink but that should improve reliability (Everything electrical you’ve ever owned likely failed due to overheating, or the cheap power supply giving up). You can add three more B300K batteries giving near 12 kWh of available power – Which in old money is a one bar electric fire for 12 hours, enough to run an average home for a day.

All the data is available via the link above, sales blurb, tech sheets, manual etc

What am I using it for?

A UPS, although I haven’t had any power outages this year. Very unusual.

Off grid power. Look what happened in Spain. With a little more battery storage I’d only struggle midwinter. I can power an induction hob, fridge, freezer and air fryer/convection oven. Everything in the house except the hot water, storage heaters and cooker.

As cheap heating, charging the battery at the night rate (about 13p per kwh) and using the electricity to run an oil fired radiator during the day, about 34p per kwh. Even without any solar contribution this has worked surprisingly well, additional heating in late winter and the only heating as Spring warmed up. I haven’t used the woodburner since February and the storage radiators have been mostly off since March. With only one battery this probably saves very little if anything as the AC300 uses (I think) 5-10% of the power itself. However, with more batteries this equation would change and I’d have much cheaper electrical heating all day. The main benefit of this to me is not that I’m saving money on my electric bill as I’m using more electricity if I’m using the storage radiators as well. However, I’m not using the woodburner, so take into account the £20-50 per month on wood and no more ash dust coating everything, including my lungs. I will still use the woodburner but instead of nearly six months a year it will just be the coldest winter months.

Free electricity. You can run two ‘strings’ of solar panels on the AC300, each producing a max 1200 watts. In late February I temporarily setup a string of two less than £50 each 405W panels, I was impressed that they produced about 300W each at midday. I don’t know about mid December, I would imagine it’s a complete washout but my point is: Solar panels do work in Winter, it’s just the hours they produce power are limited by the length of the day.

Having only purchased this end of January I have no idea how well it will work this winter. I want to add at least one battery and am hoping it will drop in price. . . My guess is that November and December will not see much solar power generated but if I can make use of night rate electricity to heat the place during the day I’m still winning and I can always light the woodburner!

On the whole I’m very happy with it. If I had a small generator for winter/heavily overcast days I could be completely independent of the grid. I should also add that the support, both sales and technical is excellent. both of which I’ll detail in future parts.

Review of the major brands

Next part I’ll go into everything I needed to put it all together and how I set it up.

PS I paid for everything but I will be passing this onto Bluetti and if they offer me a battery I will bite their hands off.
 

© Swiss Bob 2025