Solar panels

Last year, in the face of electricity prices going through the roof, I decided to take the plunge and install solar panels on the house.  I looked at a number of systems, some with a battery, and decided that a battery system wouldn't be worth the extra expense. Back in 2018 I'd signed up to a 5-year fixed rate tariff, which runs out at the end of this month. So basically I'd still been paying 2018 prices for electricity when the price went through the roof. I decided to put the money I'd saved by doing this into solar panels so that when the tariff ended I'd be protected to some extent.

The system I installed was a 4.5kW array consisting of ten 450W panels, arranged in two strings of 5, split equally between the front and rear of the house. My roof ridge runs more or less north-south, meaning that the sloped side of the roof faces east (at the rear) and west (at the front). Essentially this means the sun hits the panels square-on from about an hour after sunrise to an hour before sunset. In other words, about as ideal as siting as you can get.

(No, that photo isn't my house, it's a free stock photo of solar panels.)

These panels run to a 3.6kW inverter. My hopes were raised when I noticed an RJ45 socket on the bottom panel of the inverter, but unfortunately this isn't an Ethernet port. It is, however, possible to plug what the manufacturer refers to as a "data logging stick" into another port. A quick investigation on Google shows that there are 4 types available, wired Ethernet, Wi-Fi, GPRS or combined Ethernet and Wi-Fi. I will be adding the Ethernet version at a future date, when I have a 'spare' £50.

The inverter then connects back to the consumer unit (aka 'fuse board' for readers not in the UK) using a 20A RCBO.

As a qualified electrician (although not trading as one) I was able to do some of the installation myself. This means the 4mm cable from the inverter back to the consumer unit is concealed rather than in surface trunking, as I was able to run the cable before the contractors arrived. Unfortunately I'm not registered as a 'solar installer' so the final connections needed to be done by the contracted electrician.

My consumer unit was installed in 2006, so was reasonably modern, conforming to the then-current 16^th Edition of the Wiring Regulations. However we're now on the 18^th Edition. I won't bore you with the minute details, but the basic difference is that my consumer unit had a 'split load' configuration, with 6 module spaces on an RCD and a further 6 for non-RCD. Nowadays a high-integrity system would be installed using RCBOs for each circuit rather than an RCD protecting a bank of circuits.

By pure chance I'd been at a well-known DIY chain shortly before the install took place, and they were selling off RCBOs for £2 each. These things are normally between £25 and £40 a pop; the type that 'well-known DIY chain' were selling had originally retailed for £25. So I snapped up a basket full of them.

A fairly technical conversation with the electrician sent by the solar contractor resulted in him leaving me a length of replacement busbar to go into the consumer unit so it could be reconfigured. There's now a bank of RCBOs for final circuits, the RCBO for the solar inverter and MCBs (non-RCD protected) for 'critical' circuits such as internal lighting and servers. As an added bonus, if an individual circuit trips with an earth fault, it no longer takes out everything. So spilling cleaning fluid into the gas hob (which has an electric igniter) now no longer cuts the power to the rest of the house!

The more eagle-eyed readers may have noticed that the ring circuits terminate on an MCB, not an RCBO, and thus aren't RCD protected. When the consumer unit was installed in 2006, the ring sockets were initially connected to the RCD. However when they were energised, the RCD immediately tripped. (It worked before, guv!) Upon later investigation I discovered that the numptie who had wired in the boiler (before I bought the house) had crossed the neutral and earth. Because this is a PME (officially called a TN-C-S) supply, it of course will function perfectly, until the system is upgraded to include an RCD! I've now found and isolated the problem, and I have two extra 32A RCBOs to fit into the board in place of the MCBs. That's a job for the future. (As is re-labelling the board - I know what all the circuits are for, but nobody else will figure it out!)

Anyway, the installation went without any problems and was all commissioned just fine. At this stage I'm not getting any payments for exports (I'm working on that) but am making savings on my electricity bill.

So to find out how much I'm saving, I used the entirely non-scientific method of comparing the number of units used against the same billing period for the previous year. Remember that until the end of this month I'm still paying 2018 prices, so 18p/kWh.

In December 2022 (the worst time for solar) the system still covered 15% of my electricity usage.

By April 2023 it was covering half of it.

During June 2023 (the best time for solar) the system was generating the full 3.6kW for most of the day, and covered nearly 70% of my electricity use.

Again, this has been worked out by comparing the number of kWh imported from the grid against the same period last year. Prior to the system being installed, my monthly bill was around £110. Subsequent to the installation, even in December the monthly bill was around £85, and for June it was less than £40.

This is without taking into account exported electricity. At present I have a first generation smart meter which can only be used by the company who fitted it (but it will record exports). I'm currently involved in a struggle to get British Gas to upgrade it to a second generation unit so I can purchase electricity from one company (at the lowest unit rate) but sell it back to another (whoever offers the highest rate). I'll post something about that when it actually happens, British Gas have told me they need to change the gas meter first, then change the electricity meter.

I'd imagine once the export tariff is set up I should get a few quid back. Not going to make a fortune on it, but enough to offset against other expenses.

Fingers crossed there's no hold-ups with this. I'll post an update when there's something to update.