One of the most common questions people ask when they see our little PV setup is ‘what will it power?’, and the answer is always a bit vague, because I know people are hoping that those little panels might be what they need to disconnect from the grid and live a life of bill-free enjoyment whilst carrying on as they were.
Bill free enjoyment is a possibility, but only – and it’s a big only for some – if you adjust your consumption according to your generation. Home generation is a great teacher – use too much, the lights go out. However it is possible to do, if you follow some basic rules.
1 – Use less. A lot less. You’re going to need LED bulbs in your lights for a start, and in a typical house, less of them. In a room with 4 fittings, fit 3 bulbs. Turning them off when not in use goes without saying.
2 – Appliances. Your fridge needs to be A+ rated minimum, be kept frost free, and the door shut whenever possible. Washing machine – very low temperature or cold washes, unless you have a bigger PV setup. If you’ve a freezer, then again, A+ rated, well maintained. Microwaves, kettles, irons, tumble dryers etc are a no-go, but we live quite cheerfully without them.
3 – Eliminate all your standby items. I didn’t realise our wireless router used 2 KwH of electricity every 24 hours until I checked. To a battery system thats a lot, and its nearly £100 a year. To save missing anything we turn off our sockets at the fusebox every night. Extreme, but it saves wandering around doing them individually (and you’ll use a lot less power).
So you’ve reduced your consumption drastically. Now you need some kit. There are a million articles out there about the nitty gritty of these systems, and I strongly recommend you get a copy of Off the Grid.
First, panels. We have two 80w and two 90w panels, a total of 340 watts. Panel prices have come down a lot, and you’ll find them on ebay, and the Bimble Inn has some used ones at very low cost.
Next, you need a charge controller, to manage what is going into your batteries. Our panels are wired in two pairs, and each pair has its own Victron Blue MPPT controller (Maximum Power Point Tracking – which can get more from your panels, especially in poor light conditions). They are simple, low cost (compared with other MPPT controllers).
Now, batteries. Ideally you need proper deep cycle batteries, that are matched to your panels and controller. We use four Elecsol AGM 135Ah batteries, which aren’t cheap, but will last.
The last part of the system is an inverter, to turn your 12v DC into 240v AC. You need a pure sine inverter – all the cheap ones you’ll find on ebay are modified square wave, and really aren’t up to the job. LED bulbs don’t like them a lot. We use a used 500W marine inverter, which performs well.
The inverter output then runs through a standard consumer unit and out to your home. It goes without saying that these circuits must be completely independent from any mains wiring, and that any connection should be made by a competent, qualified electrician. It is my understanding that building regulations Part P covers electrical installations in the home, and that this covers on and off grid supply, so do be careful. Of course, whether you choose to abide by regs is a matter of personal choice, competence and circumstance 😉
Legally speaking, I’m not encouraging any reader to do anything that might be illegal or dangerous, and this post is for information purposes only.