I have a blank slate situation. I'm about to setup an auction caravan as permanent part time accommodation for a grandson. The search for the van is underway. I have a location picked out that will have a good sky window 7 hours a day. I'm on acreage just south of Brissy. I do want to install an aircon. So, I'm asking for some feedback on what current users have in Watts of Solar and Ah in LiFePo to run a gas house with a 2500 inverter aircon.
Grandson is doing FIFO so 5 days here each 14 and the van will be his base. The van will have a Safari roof. I'll start with panels flat on the roof and set up a rack later to adjust angle to the sky to optimise for seasons. The one power requirement that is hard to predict is the grandson's stated intent to have a HUGE TV screen to play games on.
Right now, I'd like to know what size setups people are using that support the house and to run an Aircon. I have no worries about weight or space for batteries or will have plenty of real estate for Solar panels. I'm in design mode and will likely overengineer if I don't get some practical examples of currently working setups.
Cheers
Iza
How much do I need, Solar and Battery bank?
-
- Posts: 169
- Joined: Wed Dec 05, 2012 4:28 pm
-
- Posts: 8784
- Joined: Mon Nov 26, 2012 7:00 pm
- Location: Home on the beautiful Gold Coast for a while.
- Has thanked: 81 times
- Been thanked: 66 times
Re: How much do I need, Solar and Battery bank?
Iza, can you get onto that Qld Govt scheme that is just about giving away solar, or no?
Otherwise, fill up the van roof with panels and work back from there.
Otherwise, fill up the van roof with panels and work back from there.
Cheers
David
David and Terrie
2006 Winnebago Alpine
Not all who wander are lost.
David
David and Terrie
2006 Winnebago Alpine
Not all who wander are lost.
-
- Posts: 169
- Joined: Wed Dec 05, 2012 4:28 pm
Re: How much do I need, Solar and Battery bank?
The van is a standalone thing and gets around a whole pile of Council restrictions. Incidentally, the Govt thing is mostly very complicated and does not apply in any way for what I'm doing. I have recently put Panels on the house plus batteries and did get a rebate on the batteries.supersparky wrote: ↑Mon Aug 18, 2025 3:49 pm Iza, can you get onto that Qld Govt scheme that is just about giving away solar, or no?
-
- Posts: 4674
- Joined: Thu Apr 11, 2013 6:37 pm
- Location: bedford
- Has thanked: 42 times
- Been thanked: 36 times
Re: How much do I need, Solar and Battery bank?
I have 1.2kw on the roof, 300ah at 24v lithium.
It's not enough to run the ac constantly in low/mid light, while using other things.
The thing that knocks you Round is the night time power consumption that needs to be replaced.
It's not enough to run the ac constantly in low/mid light, while using other things.
The thing that knocks you Round is the night time power consumption that needs to be replaced.
-
- Posts: 15963
- Joined: Fri Nov 23, 2012 3:44 pm
- Location: Mannum South Australia by the beautiful Murray River
- Has thanked: 50 times
- Been thanked: 30 times
Re: How much do I need, Solar and Battery bank?
My advice after actually using this method and proving it works, get a salvage EV from Pickles Auctions that has V2L capability .... I'm using an MG4 so I can tell you first hand how well that works.
There are two commonly available battery capacities, the 51kwh LFP battery at the poverty pack end of the scale, and the 64kwh NMC battery that powers most of the other spec models ..... they do make a 77kwh long range version, but there aren't a lot of them out there so not a lot of hope scoring one as a salvage title that gives you lots of battery for your buck.
The 51 LFP that we have is equal to very close to 4,000Ah @ 12v .... that's a lot of capacity and the V2L is capable of supplying 7kw @220vac down to 25% SOC, so roughly 38kwh useable ..... Now you need to figure out what air conditioning unit to use so you can get an idea of energy requirement.
At the moment, we have a 5kva Victron inverter and 600Ah @ 12v nom. Sodium ion batteries for base power and the 3100Ah @ 12v nom. useable down to the 25% SOC auto shut off the MG4 system.
The Victron inverter output at max supplementing the 7kw from the MG4 give a max load power available of 11.5kw, enough to run everything at the same time, the 3 way fridge on AC power, the hot water on AC power, the Ibis 4 rooftop rattler, the coffee machine, the kettle, toaster and air fryer ..... the only issue is the Winnie RCD in the powerboard/cupboard tends to freakout on overload every so often .... I'll need to upgraded the 240vac cabling to 3.5mm sq or 5 mm sq between the inverter and powerboard before I'm game to up the capacity of the RCD.
As far as solar, my choice is to use Victron 250/100 MPPT solar controllers. This allows up to 230vdc open circuit series string ...... the 20vdc leeway between the solar panel manufacturers open circuit voltage total and the MPPT max input voltage is to allow for those odd freak solar conditions, raining and the cloud parts to allow mid day sun onto cool panels, the voltage output can exceed the manufacturers specs.
It very much depends on what voltage house battery you choose, 12v nom. would see 13vdc charging x 100 amps =1300watts of solar throughput, allowing for 90% efficiency from the solar panels in the real world comes out at 1500w of solar panels per controller before the peak output gets clipped by the controller.
Double that solar advertised watts capacity if you choice to go 24v house batteries, or 3000w before output clipping occurs, if you choose to go 48vdc house batteries, 6000w advertised solar capacity per controller. They can each handle more than that and the max output from the solar only happens for a short period in the middle of the day, the controllers will simply clip off the excess it can't handle ....
The newer Victron system uses blue tooth between each unit to build an integrated network that can combine a lot of MPPT controllers and have them all working at their best along with adding the blue tooth unit to the inverter and it will show you everything that is happening on your phone or computer .....
Jon will be so happy with the length of this post
T1 Terry
There are two commonly available battery capacities, the 51kwh LFP battery at the poverty pack end of the scale, and the 64kwh NMC battery that powers most of the other spec models ..... they do make a 77kwh long range version, but there aren't a lot of them out there so not a lot of hope scoring one as a salvage title that gives you lots of battery for your buck.
The 51 LFP that we have is equal to very close to 4,000Ah @ 12v .... that's a lot of capacity and the V2L is capable of supplying 7kw @220vac down to 25% SOC, so roughly 38kwh useable ..... Now you need to figure out what air conditioning unit to use so you can get an idea of energy requirement.
At the moment, we have a 5kva Victron inverter and 600Ah @ 12v nom. Sodium ion batteries for base power and the 3100Ah @ 12v nom. useable down to the 25% SOC auto shut off the MG4 system.
The Victron inverter output at max supplementing the 7kw from the MG4 give a max load power available of 11.5kw, enough to run everything at the same time, the 3 way fridge on AC power, the hot water on AC power, the Ibis 4 rooftop rattler, the coffee machine, the kettle, toaster and air fryer ..... the only issue is the Winnie RCD in the powerboard/cupboard tends to freakout on overload every so often .... I'll need to upgraded the 240vac cabling to 3.5mm sq or 5 mm sq between the inverter and powerboard before I'm game to up the capacity of the RCD.
As far as solar, my choice is to use Victron 250/100 MPPT solar controllers. This allows up to 230vdc open circuit series string ...... the 20vdc leeway between the solar panel manufacturers open circuit voltage total and the MPPT max input voltage is to allow for those odd freak solar conditions, raining and the cloud parts to allow mid day sun onto cool panels, the voltage output can exceed the manufacturers specs.
It very much depends on what voltage house battery you choose, 12v nom. would see 13vdc charging x 100 amps =1300watts of solar throughput, allowing for 90% efficiency from the solar panels in the real world comes out at 1500w of solar panels per controller before the peak output gets clipped by the controller.
Double that solar advertised watts capacity if you choice to go 24v house batteries, or 3000w before output clipping occurs, if you choose to go 48vdc house batteries, 6000w advertised solar capacity per controller. They can each handle more than that and the max output from the solar only happens for a short period in the middle of the day, the controllers will simply clip off the excess it can't handle ....
The newer Victron system uses blue tooth between each unit to build an integrated network that can combine a lot of MPPT controllers and have them all working at their best along with adding the blue tooth unit to the inverter and it will show you everything that is happening on your phone or computer .....
Jon will be so happy with the length of this post

T1 Terry
A person may fail many times, they only become a failure when they blame someone else John Burrows
Those who struggle to become a leader, rarely know a clear direction forward for anyone but themselves
Those who struggle to become a leader, rarely know a clear direction forward for anyone but themselves
-
- Posts: 169
- Joined: Wed Dec 05, 2012 4:28 pm
Re: How much do I need, Solar and Battery bank?
Wow, that pulled me up. Thanks for that practical example.
-
- Posts: 169
- Joined: Wed Dec 05, 2012 4:28 pm
Re: How much do I need, Solar and Battery bank?
Me too, Terry. Currently trying to find a slightly simple solution. My house system installer guy ($230 an hour) has weighed in and provided a lot of historical data and monitoring data from systems he has installed in this location.
My drawing board is now listing possible solutions from dead simple to needing a consulting engineer.
-
- Posts: 169
- Joined: Wed Dec 05, 2012 4:28 pm
Re: How much do I need, Solar and Battery bank?
For those who might be interested, Auction sites around Brisbane have shown up several vans for sale on consignment. I'm now looking at suitable, unroadworthy, repairable, slightly sad vans between $2000 and $3000. My Solar budget just opened up.
I'm on 5 acres and have been considering a Granny Flat for some time. DA fees for a GF here run to $22,000. Still very early days but I'm hopeful of putting in my van project for under $10,000.
Iza
I'm on 5 acres and have been considering a Granny Flat for some time. DA fees for a GF here run to $22,000. Still very early days but I'm hopeful of putting in my van project for under $10,000.
Iza
-
- Posts: 15963
- Joined: Fri Nov 23, 2012 3:44 pm
- Location: Mannum South Australia by the beautiful Murray River
- Has thanked: 50 times
- Been thanked: 30 times
Re: How much do I need, Solar and Battery bank?
Does that include the solar and batteries? If it is, save yourself a whole lot of time and simply forget itIzabarack wrote: ↑Tue Aug 19, 2025 6:06 am For those who might be interested, Auction sites around Brisbane have shown up several vans for sale on consignment. I'm now looking at suitable, unroadworthy, repairable, slightly sad vans between $2000 and $3000. My Solar budget just opened up.
I'm on 5 acres and have been considering a Granny Flat for some time. DA fees for a GF here run to $22,000. Still very early days but I'm hopeful of putting in my van project for under $10,000.
Iza

Your solar guy charges $230 hr ..... I certainly was underselling my services .....
T1 Terry
A person may fail many times, they only become a failure when they blame someone else John Burrows
Those who struggle to become a leader, rarely know a clear direction forward for anyone but themselves
Those who struggle to become a leader, rarely know a clear direction forward for anyone but themselves