I built a DIY Solar Power System!

I want to preface this video with a clear disclaimer. This is not a step by step tutorial. This is not expert advice. Electricity can be literally deadly, so unless you are already very comfortable working with both DC and AC power sources, lithium batteries, wiring and your local requirements, just hire a qualified electrician. Your life isn’t worth the few quid you’d save not hiring a professional. Right, now we have that clear, let’s get building!

As mentioned in the previous video, I am building an off-grid system. That means I won’t be connected to the mains grid, nor my standard house wiring. I’m running everything from my shed and into my house, with the aim of keeping it relatively low cost while still being able to offset a reasonable amount of my energy bills. I’m not installing these on my roof either, no the first job here is building a frame to fit two of the three panels I’ll be using on.

I’m only cutting the pieces that are the length of the panels, around 1.7m, as I’m going to trim off the excess from the width of the two panels plus their brackets later. I do need to cut the diagonal stakes too, as with most DIY projects there are countless ways you could do it but I had my jigsaw handy so that’s what I went with. Next is painting both the pressure treated wood I’ll be using as my upright posts and stakes, and the standard dimensional lumber for the frame itself. I did a few coats of the same treatment the shed has so they should be a relatively close match colour wise.

For sizing up the frame, we stuck the Renogy mounts to the back of the Trina 400W panels I’m using here, then laid out the wood and panel to get a good idea for sizing and spacing. I’m using stainless steel screws, bolts, washers and nuts here so they have the least chance of rusting and tarnishing in the weather. I’m just using butt joints here as the panels really aren’t that heavy so I don’t foresee much of an issue with that. We attached the central support beam, then laid the next panel down to size out the final strut. Once that was attached, we attached the panels to the frame. While the fasteners in the Renogy mounting kit are self tappers, I always like to pre-drill holes so I don’t split the wood.

With the panels attached, the next thing to do is dig some holes for the posts. I wanted to wait to have the frame built before fitting the posts so I could get them as square as possible. So, time to get digging! With the posts sunk into the ground and stakes driven in, we then positioned and mounted the frame using stainless steel M8 bolts, nuts and washers. The aim here is for this to be adjustable so later in the year I can have it at a steeper angle later in the year when the sun is lower in the sky. We did also mount the third panel on the shed roof!

With those on, we got the Renogy Rover 60 Amp MPPT charge controller mounted, then started assembling the battery. It’s really important to connect the battery to the charge controller first before the solar panels get connected. I attached all the bus bars and balance leads for the BMS, then the battery leads for the charge controller. That let the charge controller switch on, where I could set the battery type and capacity. We then hooked up the solar panels and started making 500W of power instantly!

One part of the build I didn’t film was hooking up the inverter and the in-house wiring. I’m using armoured cabling from the shed to a junction box outside the house then standard twin and earth inside the house. I made the mistake of buying a modified sine wave inverter first, so had to return it and get a proper pure sine wave inverter instead. This one is rated for 3000W continuous or up to 6000W peak for about 10ms. That’s plenty for the single 13A plug face I’m planning on running this with.

Something I want to note about the battery setup is that this BMS, despite having the balance leads connected and capable of balancing… it just won’t. So I bought a separate balance board which has been fantastic. The BMS still protects from under and overvoltage, over charge and overdischarge, it just doesn’t also balance the cells.

So, how much power am I making? Well, the charge controller reported a peak of 1310W – that’s about 10% more than the panels are rated for which is amazing. As for how much power I’m using, as it stands I’m running my AC, my fridge and my washing machine off of it. I’m going to be doing a third video making the whole system a bit “smarter” and connected to Home Assistant, so I can monitor battery capacity overnight and see if it makes sense to also move the 300W of PCs running 24/7 in my office to it too for even better power savings.

Finally, let’s talk cost. I spent £717 on the three Trina Vertex S 400W panels, including £110 for delivery. The charge controller was £220, and another £90 for the mounting kit including the long MC4 leads and battery hookup leads. The EVE 280Ah cells were £171 each after tax and delivery, so £1,368 total, the BMS was around £128, the balance board was £32, the cable entry glands were just shy of £20, the stainless steel bolts, nuts, washers and screws were around £20 for the lot, the wood was right around £100, the inverter was £306, I also bought some extra MC4 cables for £17 each, and I spent another £40 or so on the cabling and plug faces. All of that adds up to just shy of £3,000.

Now the big question, what’s my return on investment time? Well, if I can offset an average of 400W all day every day – something I think is pretty achievable with the panels and battery specs – especially at the new rate for electricity starting in October, I’ll have made my money back in a year and a half. If Ofgem doubled the price cap again in January like we expect, then it’d possibly be under a year. For context, I’m generally using between 700 and 800W pretty consistently in my house, so cutting that in half literally halves my bill. The other benefit is that should we have any issues with the grid dropping out – especially in January – we now have a backup solution that will keep everything essential running.

So that’s a look at my new solar power system. I’m going to do a follow up video adding some “smarts” to this so I can monitor and track everything in Home Assistant, so make sure you are subscribed so you don’t miss that. I’m going to go into more detail on the energy and cost savings in that video too as I’m hoping to track all that.