Off-grid solar system update

[chrrris]

Back in october of last year, I posted on here about my little experimental DIY off-grid solar system that I was building. I thought it was time for an update, as I’ve got more data and more experience now.

Raw data wise, this is the typical ON-GRID daily kWh electricity usage for the house from Feb 2020 to now (i.e. the stuff I had to pay for, that I didn't generate myself):-

solar-Aug2022.png (36.84 KiB) Viewed 2212 times

Obviously, all the peaks are the winter months, and the troughs are the summer. As you can see, the simple job of replacing all of the light bulbs (or “lamps” as the more pedantic might prefer them to be called) in the house with LEDs saved me approximately 700Wh per day in the summer and 900Wh in the winter. Given the current, and the forthcoming, prices of retail electricity, it’s a no-brainer for everyone to do this now. It’s well over a quid a week saving, and will soon be closer to a fiver a week saving.

For the solar system (reminder: a single 360W panel with a single 120Ah marine battery as storage), our daily usage went from 7.8kWh during winter 2020/2021 to 7.0kWh during winter 2021/2022. And, as you’d expect from solar, a bigger saving from 6.2 to 5.2kWh during the summer period.

Overall, these changes represent a 19% saving in winter, and 24% in summer. For an outlay of just under £1000.

When I started this solar experiment 10 months ago, I think it’s fair to say it was arguable whether it was worth it from a purely cost-saving point of view (based on the energy prices at the time). This wasn’t really my reason for doing it, as I was more concerned about forthcoming grid outages being a problem (they won’t be cutting off domestic gas this winter, as it’s too dangerous and/or costly when it comes to restoring it – they’ll cut off the electricity to stop people being able to run their gas boilers). However, it’s been such a success, and the world has changed in such a huge way since then, that I’m now upgrading the system as follows:-

I’ve just (as in yesterday…) added a second marine battery in series, switching from a 12V system to 24V. This also necessitated a new inverter: from a 1500W 12vDC model to a 2000W 24vDC. I’m currently waiting for a second 360W panel to help keep this new, larger, system charged during winter. And I’ve refined a bunch of things such as replacing the in-line fuses with DC circuit breakers, and building a separate cupboard for the batteries.

Complete shopping list for the new, improved, system is:-
Two 360W Panels @ £299.99 = £599.98
Two 120AH Deep-cycle marine batteries = £239.98
2000W 24vDC to 240vAC Inverter = £254.99
12/24V MPPT Charge Controller = £97.98
WiFi Monitoring/Logging Thingy = £23.99
Aluminium Brackets for Panels (£39.99 x 2) = £79.98
Misc Solar Cables and Connectors = £50 ish
Timber, screws and paint for cabinet = £120 ish
Sockets/pattress/Conduit/Cable/Sealant/breakers = £100 ish

Total: £1566.90.

I don’t know how much this newer, 2 panel system is going to generate yet (still waiting for the arrival of the 2nd panel for starters) but I know it will save me more than the circa 22% the existing setup saves. Even putting aside the protection from national grid outages (they’re coming…) that lot will pay for itself in a year or so. And the additional feeling of independence from outside influences is priceless.

Hope someone finds this useful. By the way, I'm not in the least bit interested in any happy-clappy "green" nonsense. This is more a case of ensuring my family can stay warm, eat, and survive relatively comfortably in the coming months/years; solar panels, Chinese electronic devices, and lead-acid batteries aren't, in my opinion, "green", and that fact doesn't bother me in the slightest.

[Razor]

I must have missed the original thread. Will go back and read it later but this is very interesting thanks for posting

Getting off grid might well become a necessity for all of us soon.

[Neelix]

Out of interest what are you powering with your off grid system ?

[chrrris]

Out of interest what are you powering with your off grid system ?

With the previous 12V setup, in the winter: Fridge/Freezer plus charging for mobile phones and laptop is about all it can realistically handle. In the summer, all of that plus my desktop PC and internet gubbins (router and DSL box, etc). The desktop PC I'm on right now is being powered by it, in fact. Obviously the glorious summer weather has helped a lot -- currently getting around 1.5kWh/day out of that one big panel and it's in a far from ideal location.

The new system should give me double the juice (or just above double as I believe a 24V system is a bit more than twice as efficient as a 12V). Easily enough to also drive the electrics for the gas boiler in winter (although I have a coal/log fire that will be used if the gas prices go crazy), and hopefully TV too.

I know people in South Africa and they're currently having rolling blackouts there (1.5 hours at a time, three times a day). This sort of system will easily smooth the gaps in that sort of situation. Getting by on a system like this alone would be trickier. It's tempting to hire a scaffold tower and put the panels on the apex of the main house, rather than the ground floor extension where they are at the moment, but there are planning issues involved with putting off-grid panels more than 4m above the ground.

As an aside, I've learned a bit from the situation in South Africa. Their water supply is contaminated because the rolling power cuts have affected the water processing plants. The official solution is "boil tap water before drinking it" -- tricky to do in the event of a power cut!

[Neelix]

My tied system cost about £4200 3 years ago for a 16A set up

I’m a spark so did all the electrics my self, and that figure includes scaffolding, paying a mate to help me, mesh around the panels and the divertor to the immersion heater

Very happy with the output / set up

No FIT

[chrrris]

Yeah, I think you can save a lot of money by doing the installation and design work yourself. Obviously that's not possible (well, not legally) if you're not a spark unless it's isolated from the grid.

Does your tied system still work in the event of a power cut? I have a mate who had a grid-tied system installed recently and was shocked that it doesn't include any provision to switch the supply off grid in the event of a power cut. He said it would've been another 4 grand to have the gear to do that installed, which seems insane to me and takes away one of the biggest advantages of generating your own power. Looks like you can get automatic transfer switches for around £100 so I'm not sure where the other £3900 comes from -- installation, testing and certification??

[Neelix]

Yeah, I think you can save a lot of money by doing the installation and design work yourself. Obviously that's not possible (well, not legally) if you're not a spark unless it's isolated from the grid.

Does your tied system still work in the event of a power cut? I have a mate who had a grid-tied system installed recently and was shocked that it doesn't include any provision to switch the supply off grid in the event of a power cut. He said it would've been another 4 grand to have the gear to do that installed, which seems insane to me and takes away one of the biggest advantages of generating your own power. Looks like you can get automatic transfer switches for around £100 so I'm not sure where the other £3900 comes from -- installation, testing and certification??

Tied systems need 230v to operate.

I suspect you need a battery system plus extra kit to make this work, and hence the 4K price tag

[chrrris]

Tied systems need 230v to operate.

I suspect you need a battery system plus extra kit to make this work, and hence the 4K price tag

Yes, it definitely did need a battery too -- but he was quoted another 7 grand for that (some fancy tesla LiFePO4 system in a sleek looking wall-mounted box)!! The £4K was literally just the gubbins to isolate his solar from the grid and keep everything running in the event of a power cut. You probably underestimate just how much you've saved yourself by doing all the work yourself -- these solar installers are charging big $$$$ right now. I think you'd be looking at the wrong side of £20K for a typical household grid-tied solar system install, plus maybe another £10K to be able to use it in a power cut. Mind you, even a £30K system will pay for itself eventually if the prices continue to go the way they're heading...

[Neelix]

Tied systems need 230v to operate.

I suspect you need a battery system plus extra kit to make this work, and hence the 4K price tag

Yes, it definitely did need a battery too -- but he was quoted another 7 grand for that (some fancy tesla LiFePO4 system in a sleek looking wall-mounted box)!! The £4K was literally just the gubbins to isolate his solar from the grid and keep everything running in the event of a power cut. You probably underestimate just how much you've saved yourself by doing all the work yourself -- these solar installers are charging big $$$$ right now. I think you'd be looking at the wrong side of £20K for a typical household grid-tied solar system install, plus maybe another £10K to be able to use it in a power cut. Mind you, even a £30K system will pay for itself eventually if the prices continue to go the way they're heading...

You need to get proper quotes because I think your prices are way too high unless you are in London

[chrrris]

You need to get proper quotes because I think your prices are way too high unless you are in London

This isn't me, these are the prices quoted to my mate who's just outside of London in Crawley. Trust me, he shopped around. Google the current install price for a Tesla Powerwall.

[Neelix]

You need to get proper quotes because I think your prices are way too high unless you are in London

This isn't me, these are the prices quoted to my mate who's just outside of London in Crawley. Trust me, he shopped around. Google the current install price for a Tesla Powerwall.

There are other battery solutions and yes the Tesla isn’t cheap