So you want to make your own DIY Solar Power System….

So you want to make your own DIY solar power system… Here’s what you should know! I’ve just built my own off-grid system – and yes I’ll have a full video on exactly how I did it – so I’m in a good position to run down the main things you should know, starting with the biggest one: grid-tie or off-grid. Grid-tie means the power generated by your solar panels connects to your standard house wiring, and more importantly gives you the ability to sell any excess energy you make back to the grid. By comparison, off-grid means you won’t be using your standard house wiring, but that works well for renters (like me) and is a fair bit cheaper.

Grid-tie is what you’ll find professional solar installers will use. It’s the most long-term cost effective as you can not only offset your entire electricity bill, but even sell any excess off the top to help recoup the cost. Sadly, this is the more costly route. Generally you’d only do that if you owned the house, why spend money improving someone else’s property? The biggest reason for that cost is you’ll need a considerably more expensive inverter, battery system and more solar panels too, plus a certified electrician to not only at least hook up the grid-side wiring, but also to give you an MCS installation certificate, apply to your local DNO (district network operator) for approval and apply to your electricity provider for an SEG (smart electricity guarantee).

By comparison, an off-grid solution can be as big or as small as you like. It’s also much easier to make it a semi-temporary setup like mine, so it’s a lot better for renters. That does mean you aren’t likely to offset your entire energy bill with your solar power, but you also don’t need to drop ten grand on a full system if you just want a bit of extra power to take up your base load – things like your fridge or PCs that might be running constantly. It’s also not too big a deal if you under-size your system for what you end up needing, as you can use an automatic transfer switch to switch back to mains power should your battery run out.

Ok, let me run through the main components you’ll need and what to look for on each. The most obvious start are the solar panels themselves – I’d put these into two categories: hobbyist; or professional. Hobbyist panels generally offer something like 100W of power, and tend to be considerably smaller than the more professional panels, and are great for a small or basic setup where you just want to stick a couple little panels on your shed or garage roof so you can have power there – maybe for charging motorbike or ebike batteries or even just having lighting and a bit of power available for tools.

On the flip side there are the professional panels. These are massive, like 1.8m by 1m EACH, and are generally only available from wholesalers. Most I’ve found here in the UK won’t actually sell you them directly, they only want to sell to businesses, although I’ll leave a link to the one place I found in the UK who was willing to sell me mine directly. Plus they have a pretty massive (if almost fully out of stock) inventory of options. These panels tend to output between 250 and 450W of power – mine are 400W panels, and surprisingly weren’t much more expensive than the hobbyist options. The size might make this difficult for a DIY install, as you generally find these mounted on your roof, but I’ve made it work for me. For a professional installer, these are the panels you will be getting.

Next up is the inverter. Long story short, your solar panels produce DC (direct current) power. Simple plus and minus. Your devices almost always need AC (alternating current) though, just like what the grid provides, so you need to convert that DC to AC, which is the job of an inverter. For a grid-tie system, you’ll need a relatively high end grid-tie inverter. This can be in the thousand pound plus range just for that, that’s one of the higher costs of that solution. You’ll likely want a 3-6kW inverter to be able to supply enough power to everything in your house – although if you have things like power-showers or immersion heaters that might need to either stay grid-side or you’ll need to splash out more for a higher output inverter.

If you want your battery hooked up to the inverter directly, what you are looking for is a “hybrid inverter”. Most people that sell hybrid inverters also sell you the battery packs you’ll need to use with it. Some, like Huawei’s hybrid inverters, are designed to work with crazy high voltage batteries – like 450VDc kinda high. Some are much more reasonable and want 48V instead though. If you are buying a bundle like these GivEnergy ones you don’t need to worry about compatibility.

If you are running an off-grid system, that’s generally a little easier. While you can get a hybrid inverter, they tend to be considerably more expensive than they really need to be for a simple system. I went with a relatively cheap standalone inverter and for a small system like mine that’s what I’d recommend. The one thing you should triple check before buying though is if it’s a “pure sine wave” inverter, or a “modified sine wave” inverter. You want the former. “Modified” sine wave inverters will be cheaper, but they can also damage or brick your devices – especially things with motors or sensitive electronics. Trust me, spend the extra and get a proper pure sine wave inverter instead.

Moving onto the battery storage, this is also a bit complicated so bare with me. First things first, AC or DC? If you are going for the minimal route, you want DC. If you are buying a hybrid inverter and battery kit, you get what you get. If you are going with a grid-tie system you can use either. AC batteries – like Telsa’s Powerwall 2 – have inverters built into them, and are connected to a controller that manages where the energy goes and if you need to use any grid power. These are considerably more expensive thanks to having a full inverter built in, but they are designed to work with a full system so it should work well for a professional installation.

DC batteries, especially for smaller systems, can technically be anything including deep cycle lead acid style batteries. Trust me when I say you don’t want that. Lithium, especially LiFePo4 batteries are what I’d recommend. You can buy pre-made battery packs, including from AliExpress if you are willing to wait for a significant cost saving, or if you are experienced enough you can build your own pack like I did. I can’t really recommend that though. Electricity is literally deadly if you aren’t careful, so if you aren’t already confident in working with electricity, especially DC batteries like this, just buy a pre-built pack. You can even buy server-rack batteries which makes mounting nice and easy!

If you go with a small off-grid system and want to use a separate inverter, you’ll need a way to get the power from your solar panels into your batteries. That’s where a solar charge controller comes in. There are two categories for this, PWM and MPPT. You want the latter. MPPT, or maximum power point tracking, is the more advanced way for the solar power to be DC to DC converted from, in my case, 120V 10A DC to more like 28V 43A for the battery. It generally has the best efficiency, so is definitely worth spending the extra over a more basic PWM option. You’ll need to pay attention to a few of the specs, like the maximum current, voltage and what battery voltages it can support. The Renogy model I have supports anything from 12V to 48V batteries, and will charge at up to 60A meaning a maximum of 1600W with a 24V battery. That works for me since I’m using three 400W solar panels, but if I needed a 12V battery instead I’d either need to only use two panels or buy their higher end 100 amp unit instead.

A few notes on some of the other parts you’ll need, like connectors, isolators and cabling. It’s best practice to include a DC isolator switch for at very least your solar panels. I currently don’t have one installed, although it is something I’m planning on adding in soon, and if you are building your own it is something I’d recommend. The panels will almost always use MC4 connectors, you might need to pick up some spares although happily they aren’t too expensive to buy pre-made. If you are willing to buy a crimping tool you can make the cables yourself – although make sure to use the appropriate wire gauge. The thinner the wire and the higher the current, the more heat it’ll output. The more losses you’ll have, and the higher risk of a fire, short or other major problems. For AC cabling, if you are running it outside I’d highly recommend getting armoured cabling. It isn’t all that expensive, I got a 10m reel for £19 and that’s plenty to get the power from my shed to the house. You’ll also want to make sure you are using cable entry glands for cables coming into or out of enclosed/dry spaces. They aren’t expensive and it’s well worth it. Oh and make sure to put them on BEFORE connecting your cables!

I want to talk a little about mounting the panels themselves. If you are having a professional install it, odds are that’ll be on your roof. A south facing roof (in the northern hemisphere anyway) is ideal but your installer will work that out. If you are DIYing it, you have plenty of options. You can build a frame to stick up as a car-port or garden shade, you can mount them to a garage or shed roof (preferably your own…), or mount them to your roof if you are able to. As for mounting the inverter, charge controller and batteries, the first thing is obviously a dry indoor space. That can be in the garage, a shed, an exterior storage space, whatever, but it should be protected. The second point is that they should be reasonably close to your solar panels. The lower the voltage the higher the current, and the higher the current the less efficiency you’ll get especially over long lines. It’s better to have a long 240V mains AC line with short DC lines, than the other way around.

Ok, that’s a whole lot of information, so I’m going to leave it here. The next video in the series will be all about my setup – actually setting it up, getting it powered on and running some of my stuff. Make sure you are subscribed so you don’t miss that!