Mon, 20 Apr 2026 13:21:50 +0100 https://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17999&Focus=303913#Comment_303913 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17999&Focus=303913#Comment_303913 Wed, 18 Oct 2023 19:52:40 +0100 LouiseSJPP As it turns out, things are not that straightforward. The electricity in the state we live in, Navarra, is 100% renewable. The price is stupendously low: 4c per kw/hr. There is no home-generation buy-back: you can offset your own consumption to some extent, but no more. This means there is neither an economic case to be made for a solar installation nor an ecological one.
What we do have instead is a practical case. We have a 25amp mains supply, and to upgrade it would be very expensive. It's also unreliable, subject to failure in wind and rain, and sometimes for long periods, living in the wilds as we do. We remain interested in an almost offgrid installation.
However, we have many friends who all tell us how disappointed they are with their shiny new solar installations, falling far short of expectation. I don't want to make a big investment to be similarly disillusioned.
I'm wondering if there's a way to get a small installation up this winter in order to minitor performance before launching on a bigger project. The problems I see with this are the amount of kit which will either need to be bought 'full-size' in the full size in the first place, and maybe issues with measuring output in a meaningful way. Will the system have to have full load all the time in order to produce all it can, in order to measure it. How would this be done? Or can it all be modular so that putting in one panel this winter can be the start of a system which can have more panels added later? Maybe with micro-invertors, it's possible.
Have you any thoughts, advice or experience you can share?]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17999&Focus=303919#Comment_303919 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17999&Focus=303919#Comment_303919 Thu, 19 Oct 2023 08:11:50 +0100 fostertom https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17999&Focus=303922#Comment_303922 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17999&Focus=303922#Comment_303922 Thu, 19 Oct 2023 08:53:05 +0100 Peter_in_Hungary Posted By: LouiseSJPPThis means there is neither an economic case to be made for a solar installation nor an ecological one.
What we do have instead is a practical case. We have a 25amp mains supply, and to upgrade it would be very expensive. It's also unreliable, subject to failure in wind and rain, and sometimes for long periods, living in the wilds as we do. We remain interested in an almost offgrid installation.
As you say there is no real case for a solar installation.
I am assuming that the 25 A supply will suffice even if you have to schedule power hungry devices e.g. overnight charging of an EV at 16 A only etc.
Perhaps forget solar and think about a battery back up for your grid supply. Then you have to decide for how long you want to cover a power outage and what you want to run during that outage. Once you have a base load and time for an outage then look at battery options. Almost no break switchovers with alarms are readily available for grid back up. If you want to further insure against a long outage - depending on the expected frequency - then a generator might be a consideration, not very green but if you are only expecting to use it once a year or so to save the contents of your freezer then perhaps acceptable.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17999&Focus=303928#Comment_303928 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17999&Focus=303928#Comment_303928 Thu, 19 Oct 2023 13:05:28 +0100 philedge
There's plenty of hybrid inverters/ battery combos that will power significant loads when the grid goes down, but if your grid goes down in bad weather then you'll need a very big battery and/or generator as solar isn't going to be much help in bad weather.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17999&Focus=303930#Comment_303930 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17999&Focus=303930#Comment_303930 Thu, 19 Oct 2023 13:51:13 +0100 djh
I'm not sure about the 100% renewable claim, BTW. https://investinnavarra.com/en/renewable-energy/the-energy-plan-for-navarra-plans-to-mobilise-2300-million-euros-by-2026/ https://www.100-percent.org/navarre-spain/]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17999&Focus=303946#Comment_303946 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17999&Focus=303946#Comment_303946 Fri, 20 Oct 2023 09:32:58 +0100 revor https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17999&Focus=303947#Comment_303947 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17999&Focus=303947#Comment_303947 Fri, 20 Oct 2023 11:24:10 +0100 Peter_in_Hungary Posted By: revorCharging from the grid seems like your best option but you will have to decide on what size. There are a couple of issues to consider how big a capacity for storage and how much current you want to supply. If you were charging via solar a nominal 48 system you would need a sizeable inverter and hefty cabling to get say 40 amps so a 240 V battery array would be the best option. That gets you over the low voltage high current scenario and you then need to decide the size of your "bank". At nominally 2v per cell you could be talking a lot of batteries wired in series to give you the volts and paralleled to give you the capacity so not a cheap option. Used batteries from FLT ex submarine or UPS could be an option. I have no experience of these but I was aware of someone who did an array of batteries' using ex UPS batteries but being off grid charged them up with a generator driven by a tractor using diesel so not very green. UPS bats are changed well before the end of their life so are good bet if can get hands on them. Then there are ex EV batteries if you can get someone knowledgeable to configure a set up. A friend has just bought 20Kw from a scrapped BMW for his solar system linked to a 10Kw inverter but had someone supply it and configure it.
Or you just get a Tesla powerwall or SunPower SunVault, or the Enphase Encharge (others are available) get a manufactures guarantee and support, plug and play and off you go and save your self all the problems of a home brew bit of kit.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17999&Focus=303957#Comment_303957 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17999&Focus=303957#Comment_303957 Fri, 20 Oct 2023 16:14:52 +0100 revor blockquote>Posted By: Peter_in_HungaryOr you just get a Tesla powerwall or SunPower SunVault, or the Enphase Encharge (others are available) get a manufactures guarantee and support, plug and play and off you go and save your self all the problems of a home brew bit of kit.

Yes fine if you have deep pockets £900 -£1000 per kwh so looking at 3/4 Powerwalls you are looking at £30/35K + inc install for a 40kwh job that may see you with good management through a lengthy power outage.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17999&Focus=303959#Comment_303959 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17999&Focus=303959#Comment_303959 Fri, 20 Oct 2023 17:44:27 +0100 Peter_in_Hungary Posted By: revorYes fine if you have deep pockets £900 -£1000 per kwh so looking at 3/4 Powerwalls you are looking at £30/35K + inc install for a 40kwh job that may see you with good management through a lengthy power outage.
But it depends what you want out of your backup. If you are happy with lights and fridge/freezer only running for a day and postpone the washing machine and dishwasher for later then the power requirements drop drastically. Longer than a day the get the gennie out.

As with most things define the requirements first, list the nice to haves and the must haves, then look at the costings and the budget...........and then go down the pub 'cos you just realised you can't afford any of it with todays prices.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17999&Focus=303962#Comment_303962 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17999&Focus=303962#Comment_303962 Fri, 20 Oct 2023 18:41:38 +0100 fostertom