Low power demand off-grid solar?
Discussion
Hi all,
I'm (still, slowly, negotiating about being....) in the position of being able to take over a rural outbuilding to keep some of my cars in.
I think I posted a long while back asking about solar export, and thanks to everyone who replied about that and put my noob expectations to bed.
Unfortunately, it's all in vain because the power company have quoted me £31,000 + VAT to connect it to the grid, so... lol, no.
I will need basic power in there though to run some LED indoor floodlighting, a radio, run/charge up power tools, boil a kettle or occasionally use a small heater or (single phase 240v) sparkle stick/ linisher/ lathe.
The obvious solution would be a generator but that's faff, maintenance, and has an ever increasing fuel cost.
I was speaking to a friend the other day who was in a similar situation with a barn conversion house, and he spent £20k on an enormous 65kwh DIY solar and battery array and lives completely off grid - so clearly I can do similar at a smaller scale for much less cost.
I was attracted to the all in one "power wall" type systems (particularly the actual Power Wall from Tesla as it seems to have all the required "extra" gubbins on board) but I have no idea how to go about speccing the systems for what I need. Everyone's website and spec is different, and it seems a lot of systems need all sort of extra interface, inverter and management bits between the panels and the battery. It also seems that everyone wants you to "submit your postcode and house details for a quote, and see how much it'll save you on your bills"..... this is less than helpful because it's not a house, it's an outbuilding, it doesn't have an address, and what I want is vastly different to a domestic "assist" setup...
The other issue would appear to be that most, if not all of the off the shelf systems claim they are only designed as an assist, and are not meant to work in a completely self contained or off grid capacity. Is this just marketing get-out, or is there some sort of physical limitation preventing it?
Basically, all I want is... 15 (or even 10 or so) kwh of battery capacity to last me a whole (10 hour) day gentle use on one or two days a week of the above usage profile. Plus, say, 5wkh of solar panels to charge it back up over the course of the next 24 or 48 hours ready for the next visit. I'd assume that, even with solar panel inefficiency, on a 15 degree roof in the middle of winter, that should be enough recharge capacity? I'd also assume that any excess power would simply go to earth?
My friend's DIY setup used a whole cupboard full of separate but interlinked components from a company called Victron, plus another cabinet of batteries which he also has to keep insulated during the winter. But, it is 100% off grid.
From what I've seen, a 13.5kwh Tesla Powerwall is self-contained and self-heating, but is £8k plus panels, with the niggling doubt about being off grid compatible.
If I could build a Victron or similar kit for a fraction of that, then I'd be interested and would put up with the faff - but if the cost is similar then I'd be asking precisely why a Power Wall can't work standalone?
Please can anyone help advise?
Thanks in advance!
I'm (still, slowly, negotiating about being....) in the position of being able to take over a rural outbuilding to keep some of my cars in.
I think I posted a long while back asking about solar export, and thanks to everyone who replied about that and put my noob expectations to bed.
Unfortunately, it's all in vain because the power company have quoted me £31,000 + VAT to connect it to the grid, so... lol, no.
I will need basic power in there though to run some LED indoor floodlighting, a radio, run/charge up power tools, boil a kettle or occasionally use a small heater or (single phase 240v) sparkle stick/ linisher/ lathe.
The obvious solution would be a generator but that's faff, maintenance, and has an ever increasing fuel cost.
I was speaking to a friend the other day who was in a similar situation with a barn conversion house, and he spent £20k on an enormous 65kwh DIY solar and battery array and lives completely off grid - so clearly I can do similar at a smaller scale for much less cost.
I was attracted to the all in one "power wall" type systems (particularly the actual Power Wall from Tesla as it seems to have all the required "extra" gubbins on board) but I have no idea how to go about speccing the systems for what I need. Everyone's website and spec is different, and it seems a lot of systems need all sort of extra interface, inverter and management bits between the panels and the battery. It also seems that everyone wants you to "submit your postcode and house details for a quote, and see how much it'll save you on your bills"..... this is less than helpful because it's not a house, it's an outbuilding, it doesn't have an address, and what I want is vastly different to a domestic "assist" setup...
The other issue would appear to be that most, if not all of the off the shelf systems claim they are only designed as an assist, and are not meant to work in a completely self contained or off grid capacity. Is this just marketing get-out, or is there some sort of physical limitation preventing it?
Basically, all I want is... 15 (or even 10 or so) kwh of battery capacity to last me a whole (10 hour) day gentle use on one or two days a week of the above usage profile. Plus, say, 5wkh of solar panels to charge it back up over the course of the next 24 or 48 hours ready for the next visit. I'd assume that, even with solar panel inefficiency, on a 15 degree roof in the middle of winter, that should be enough recharge capacity? I'd also assume that any excess power would simply go to earth?
My friend's DIY setup used a whole cupboard full of separate but interlinked components from a company called Victron, plus another cabinet of batteries which he also has to keep insulated during the winter. But, it is 100% off grid.
From what I've seen, a 13.5kwh Tesla Powerwall is self-contained and self-heating, but is £8k plus panels, with the niggling doubt about being off grid compatible.
If I could build a Victron or similar kit for a fraction of that, then I'd be interested and would put up with the faff - but if the cost is similar then I'd be asking precisely why a Power Wall can't work standalone?
Please can anyone help advise?
Thanks in advance!
Used but good panels are easily available for £25 a panel.
Victron kit isnt bad either. I find for building small self contained offgrid setups 12v works well, if you can make as many of your loads 12v as possible you dont lose much efficiency inverting from 12v or 48v to 240v.
12 to 240 is a bit less efficient than 48 to240 so if most of your loads are 240 then start from a 48v system, but if you can run 12v lighting, a 12v diesel heater, 12v chargers for your power tools then you can build a decent system for not much money. Plus if you are going to do an extended draw just once in a blue moon you can top it up off your vehicles alternator.
You can build a victron cerbo from a rasperry pi zerl and an optocoupled usb to ttl converter. Which gives you a great dashboard to monitor everything.
Powerwall type ac coupled batteries are designed to primarily be used with a connection to the grid. They take a bit of effort to get working properly offgrid but victron do frequency control software helpers to work with them.
Sunsync is good for offgrid too, but victron is more diy friendly.
Victron kit isnt bad either. I find for building small self contained offgrid setups 12v works well, if you can make as many of your loads 12v as possible you dont lose much efficiency inverting from 12v or 48v to 240v.
12 to 240 is a bit less efficient than 48 to240 so if most of your loads are 240 then start from a 48v system, but if you can run 12v lighting, a 12v diesel heater, 12v chargers for your power tools then you can build a decent system for not much money. Plus if you are going to do an extended draw just once in a blue moon you can top it up off your vehicles alternator.
You can build a victron cerbo from a rasperry pi zerl and an optocoupled usb to ttl converter. Which gives you a great dashboard to monitor everything.
Powerwall type ac coupled batteries are designed to primarily be used with a connection to the grid. They take a bit of effort to get working properly offgrid but victron do frequency control software helpers to work with them.
Sunsync is good for offgrid too, but victron is more diy friendly.
Edited by OldGermanHeaps on Sunday 3rd May 15:11
Over Dec/Jan you'd be surprised how little energy your panels will produce, so whether it will work depends how much load you're going to be using during those times. LED lights are very efficient, but if you're wanting to do any "work" there (power tools, kettles, etc) or wanting to run any climate control (heater, dehumidifier), then you may find you need a bigger system then you're expecting.
In theory there is nothing wrong with it, I would guess you'd be looking at £3-4k for the panels (5kw, installed), and then maybe £600-700/kwh of battery storage. You could DIY it cheaper, but for an independent installer to put them in that would be ballpark figures.
I'm pretty sure Powerwalls can work in standalone mode during power cuts. Whether they can operate independently of the grid all the time you' have to check.
In theory there is nothing wrong with it, I would guess you'd be looking at £3-4k for the panels (5kw, installed), and then maybe £600-700/kwh of battery storage. You could DIY it cheaper, but for an independent installer to put them in that would be ballpark figures.
I'm pretty sure Powerwalls can work in standalone mode during power cuts. Whether they can operate independently of the grid all the time you' have to check.
Edited by Condi on Sunday 3rd May 15:18
cliffords said:
Nothing is going to be more on demand or overall cheaper than a petrol generator.
Running a small heater in January. Not on solar.
This is very true tbh. If you wanted something cheap then get a new or used Chinese 3kw generator for £300 and a diesel heater for warmth. More than enough power to boil a kettle, run a grinder, keep the lights on, and at the end of the day you just switch it off and forget about it. Running a small heater in January. Not on solar.
What about this:
https://uk.ecoflow.com/products/delta-pro-ultra - Expandable and you can charge at home and take it with you.
Or just three or four of the smaller capacity Ecoflow units.
Cheap overnight tariff, charge up, take with you. Useful around the home too.
https://uk.ecoflow.com/products/delta-pro-ultra - Expandable and you can charge at home and take it with you.
Or just three or four of the smaller capacity Ecoflow units.
Cheap overnight tariff, charge up, take with you. Useful around the home too.
Edited by Russet Grange on Sunday 3rd May 16:13
Sunsynk hybrid inverter will handle any combination of:
Mains
PV
Battery
Generator/wind
The ideal would be:
PV
Battery - check out the Fogstar 32kWh units as they offer a very good price per kWh, and more capacity is better as you’ll have good days and bad days of generation
LPG generator?
Can be completely off grid, with the generator only kicking in when needed. LPG because the fuel doesn t go off and won t attract light fingered types.
Mains
PV
Battery
Generator/wind
The ideal would be:
PV
Battery - check out the Fogstar 32kWh units as they offer a very good price per kWh, and more capacity is better as you’ll have good days and bad days of generation
LPG generator?
Can be completely off grid, with the generator only kicking in when needed. LPG because the fuel doesn t go off and won t attract light fingered types.
Edited by LooneyTunes on Sunday 3rd May 15:41
Years ago I had a lock-up garage off grid.
Some lights, SMS alarm system.
I have a boat and many friends with boats off-grid.
I have a greenhouse off grid with a bit of LED lighting and some irrigation stuff I faff with.
There is a lot of knowledge out there.
Also a lot of half-baked wibble and dated stuff.
You can do quite a bit fairly cheaply.
Old car battery, small solar panel, 12V lights is the minimum.
You can do something useful for £50.
From there pure sine inverter from about £100 to run power tools.
Victron charge controller for better control £80?
That would allow you to get a serious, higher voltage solar panel for £100 or so.
12V LFP aka LiFePO4 battery maybe £160. That would be light enough to take home to charge should you need to in winter.
IT is all a slippery slope of spending. I would suggest working out your wants and needs, then costing some options.
How many hours do you expect to need power for? for lights and tools, that gives a clue about your battery needs.
What is the background power use? e.g. powering alarms or whatever, trickle charging cars against ECU continuous drain, self discharge of batteries...
How much sun does the place get?
It's hard to generalise, because everyone is different and there are many cost/benefit diminishing returns things going on.
You pay more, the more you want to be proof against long dark spells in the winter, I know people who've spent 1000s on their boat systems but still need to run the engine from time to time. My boat has about £50 worth of solar panels, a 100Ah 12V 'leisure battery' and a cheap controller. That makes it easy to run a portable fridge in summer alongside the normal lights and stuff. That's all I need, personally.
Alternatively consider a Jackery type unit, my brother has one, he has uses for genuinely portable power.
There's always an EV with v2l capability too?
Some lights, SMS alarm system.
I have a boat and many friends with boats off-grid.
I have a greenhouse off grid with a bit of LED lighting and some irrigation stuff I faff with.
There is a lot of knowledge out there.
Also a lot of half-baked wibble and dated stuff.
You can do quite a bit fairly cheaply.
Old car battery, small solar panel, 12V lights is the minimum.
You can do something useful for £50.
From there pure sine inverter from about £100 to run power tools.
Victron charge controller for better control £80?
That would allow you to get a serious, higher voltage solar panel for £100 or so.
12V LFP aka LiFePO4 battery maybe £160. That would be light enough to take home to charge should you need to in winter.
IT is all a slippery slope of spending. I would suggest working out your wants and needs, then costing some options.
How many hours do you expect to need power for? for lights and tools, that gives a clue about your battery needs.
What is the background power use? e.g. powering alarms or whatever, trickle charging cars against ECU continuous drain, self discharge of batteries...
How much sun does the place get?
It's hard to generalise, because everyone is different and there are many cost/benefit diminishing returns things going on.
You pay more, the more you want to be proof against long dark spells in the winter, I know people who've spent 1000s on their boat systems but still need to run the engine from time to time. My boat has about £50 worth of solar panels, a 100Ah 12V 'leisure battery' and a cheap controller. That makes it easy to run a portable fridge in summer alongside the normal lights and stuff. That's all I need, personally.
Alternatively consider a Jackery type unit, my brother has one, he has uses for genuinely portable power.
There's always an EV with v2l capability too?
Condi said:
Over Dec/Jan you'd be surprised how little energy your panels will produce, so whether it will work depends how much load you're going to be using during those times. LED lights are very efficient, but if you're wanting to do any "work" there (power tools, kettles, etc) or wanting to run any climate control (heater, dehumidifier), then you may find you need a bigger system then you're expecting.
In theory there is nothing wrong with it, I would guess you'd be looking at £3-4k for the panels (5kw, installed), and then maybe £600-700/kwh of battery storage. You could DIY it cheaper, but for an independent installer to put them in that would be ballpark figures.
I'm pretty sure Powerwalls can work in standalone mode during power cuts. Whether they can operate independently of the grid all the time you' have to check.
Fair comment, but on a budget, you can have a diesel-air heater for £100 and a camping gaz stove for the kettle.In theory there is nothing wrong with it, I would guess you'd be looking at £3-4k for the panels (5kw, installed), and then maybe £600-700/kwh of battery storage. You could DIY it cheaper, but for an independent installer to put them in that would be ballpark figures.
I'm pretty sure Powerwalls can work in standalone mode during power cuts. Whether they can operate independently of the grid all the time you' have to check.
Edited by Condi on Sunday 3rd May 15:18
It is fair to say panel yields can be low in winter, FWIW, a horizontal 50w panel could yield as low as 10Ah a week at 12V on my boat, which is shaded apart from close to South. That's enough to 'tread water' and run a few hours of lights. 500W panels are cheap now, but comically inconvenient on a small boat!
A good week in Jan could be as much as 40Ah.
Amp hour meter from ebay at £15 or so is another add on perhaps?
I wouldn't hold off putting together a £300 system because a £3k system is better.
If you want to do this I would suggest looking for sailboat solar setups. Should provide all the power you want.
There are many guides on how to calculate what you need.
I find this chap very knowledgable. Lived off grid for long periods on his boat. Yes he is US based but the only difference would be the inverter to go to 240v instead of the US 120V.
https://youtu.be/avxqtbXUR30?si=DF89ZfckCQdQ3Hr2
Weather it would work in the depths of winter in the uk who knows. I would be looking at adding a small generator as an alternative to charge the batteries or use directly. Honda do some very quiet units that we see all over campsites when we go to motorsport events.
There are many guides on how to calculate what you need.
I find this chap very knowledgable. Lived off grid for long periods on his boat. Yes he is US based but the only difference would be the inverter to go to 240v instead of the US 120V.
https://youtu.be/avxqtbXUR30?si=DF89ZfckCQdQ3Hr2
Weather it would work in the depths of winter in the uk who knows. I would be looking at adding a small generator as an alternative to charge the batteries or use directly. Honda do some very quiet units that we see all over campsites when we go to motorsport events.
Edited by MB140 on Sunday 3rd May 17:17
Solar won't run much in the way of heating in winter unless you go for an absolutely huge system so it's worth stripping out that part of the demand if you possibly can.
Gas, kerosene, diesel or even a woodburner will do your heating and allow you to spec a sensibly sized solar system to run lights and top up power tool batteries at a sensible cost. If you keep the battery size to something relatively portable you can even take it off site to charge if you need to during a spell of particularly gloomy weather.
Gas, kerosene, diesel or even a woodburner will do your heating and allow you to spec a sensibly sized solar system to run lights and top up power tool batteries at a sensible cost. If you keep the battery size to something relatively portable you can even take it off site to charge if you need to during a spell of particularly gloomy weather.
There are battery powered TIG welders these days.
Also, if you can run a quiet generator from time to time without the noise or fumes annoying people, that could be part of the mix.
It can be easy to be 90% sorted with solar, hard/expensive to do 95% and borderline impossible to do 99%.
It's also a mindset thing, if you've spent a lot of time on boats in the 80s, you learn to do stuff with much less reliance on power tools.
We take the mains for granted, but we can actually live without a lot of 'stuff'.
Or there are alternatives, at a cost.
Also, if you can run a quiet generator from time to time without the noise or fumes annoying people, that could be part of the mix.
It can be easy to be 90% sorted with solar, hard/expensive to do 95% and borderline impossible to do 99%.
It's also a mindset thing, if you've spent a lot of time on boats in the 80s, you learn to do stuff with much less reliance on power tools.
We take the mains for granted, but we can actually live without a lot of 'stuff'.
Or there are alternatives, at a cost.
Everything depends on levels of usage of course but it would be doable. Panels are cheap enough so if you have the roof space go as big as you can, I would suggest plenty more than 5kw if possible to get the most performance in winter. As suggested above, the difference between winter and summer is enormous.
For storage, we have 20kwh of battery and can flatten it overnight at this time of year when the solar stops generating significantly at around 6-7pm. On a bright day it will get us through but anything less and it’s marginal. We are on Solax and the battery expansion is around £1k/5kwh so I’m considering adding 2 of them to the system.
For storage, we have 20kwh of battery and can flatten it overnight at this time of year when the solar stops generating significantly at around 6-7pm. On a bright day it will get us through but anything less and it’s marginal. We are on Solax and the battery expansion is around £1k/5kwh so I’m considering adding 2 of them to the system.
Strangely from your list of requirements the kettle is going to be the biggest issue to power via electric. As others have suggested get a gas camping stove. job done.
heating would be served well from a 5kw diesel heater
I would suggest looking at a hybrid system, small petrol generator don't use much fuel at all. Use this to power your 240v tools and to charge up a 12v leisure battery to use for lights etc. this would give you a reliable means of charging the 12v system and the extra power when needed, without solar.
I have one of these generators only 1200w but very handy when needed and very quiet. IF I had this running outside my garage for an half an hour say to charge up the battery for lights it would not be bothered by it.
https://underfloorheating.pro/products/instant-pow...
heating would be served well from a 5kw diesel heater
I would suggest looking at a hybrid system, small petrol generator don't use much fuel at all. Use this to power your 240v tools and to charge up a 12v leisure battery to use for lights etc. this would give you a reliable means of charging the 12v system and the extra power when needed, without solar.
I have one of these generators only 1200w but very handy when needed and very quiet. IF I had this running outside my garage for an half an hour say to charge up the battery for lights it would not be bothered by it.
https://underfloorheating.pro/products/instant-pow...
If you can run kettles off a gas camping stove, then you're down to just lighting and power tools. You could probably get away with having multiple tool batteries, and just running off those? Easy to charge at home, then bring in 4-8 batteries and that would cover tools for many hours. Your car(s) can recharge them too.
Welders are the exception which spring to mind. If you need to weld, that pushes up the power requirements massively. Some are now available which run from lithium batteries (£££) or from 12v batteries (£).
If you need heating, then Chinese Eberspacher knock-offs are now cheap. But a USB gilet is probably easier.
I suspect you will still want to have some "12v" solar panels to keep your cars' batteries topped up anyway, so perhaps an answer could be a few 12v solar panels to do the cars and keep a a couple of tool batteries charged up, and charge your phone.
Welders are the exception which spring to mind. If you need to weld, that pushes up the power requirements massively. Some are now available which run from lithium batteries (£££) or from 12v batteries (£).
If you need heating, then Chinese Eberspacher knock-offs are now cheap. But a USB gilet is probably easier.
I suspect you will still want to have some "12v" solar panels to keep your cars' batteries topped up anyway, so perhaps an answer could be a few 12v solar panels to do the cars and keep a a couple of tool batteries charged up, and charge your phone.
tendown said:
Can you park next to it? I believe there are an increasing number of EV's with a three pin plug socket or V2L that would run what you need.
This.My car can supply 3.6KW via the charge port, a little less via a 13A socket under the rear seat.
Plenty for running a kettle and some lights, or anything you can plug in via a normal 13A socket (welder, power tools, etc.). Combine it with a diesel heater, no need for solar or a big battery.
Charge the car at home on an EV tarrif, plug in at the workshop all day.
Should be able to find a used EV with V2L for less than the price of a big battery and solar setup that'll struggle for 4 or 5 months of the year. Basically a free car.
I found it valuable to have some permanently installed 12V lights which just worked when I opened the door and pressed the switch.
No starting generators or plugging in EVs, just a used car battery, a solar panel, a cheap regulator and some 12V lights.
You can do that for very little money, even if you need to buy the battery new.
It also trickle charged the bike that was stored there and ran an SMS alarm.
The downside is the solar panel might draw attention to a lock-up.
No starting generators or plugging in EVs, just a used car battery, a solar panel, a cheap regulator and some 12V lights.
You can do that for very little money, even if you need to buy the battery new.
It also trickle charged the bike that was stored there and ran an SMS alarm.
The downside is the solar panel might draw attention to a lock-up.
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