Solar mini split vs...

[Airman68]

I don't have the inverter switched on unless we need AC power. Only something like the mini split or microwave. The battery we have handles it easily for us.

That's kinda what I do. I don't use much AC, just for lights and tool charging. I mostly use the 12V overnight with my diesel heater. Haven't run anything really big yet.

 

[dopeassjackson]

Got my 120v mini split installed this weekend. Off amazon I ordered a glacier and received a costway, this didnt really matter to me. I did the whole install my self. With the mini split and line set cover the total cost was aboit $600. On full cool it will pull 750-800w from my batteries. On full heat is about 900w. Just low enough to run on my current 1200w inverter. This weekend I also added a 4th 235w solar pannel and swapped out my 40a CC to a 80A. Overall the mini split install was prety easy and the cost is prety compatible to a 12kbtu window unit.

The thing I dont really like is the condensor fins have no cover on 2 of the 4 sides. I'm going to change this and put lovers over the unit. In the few short hours I ran it I alreaty found a leaf stuck to it. This outdoor unit is installed under my unskirted cabin so wont get wet or have ice/snow or sun on it.

Thanks to everyone who said to skip the solar mini split. Cut the cost in more than half and I would have been running the generator anyway this cloudy weekend.

 

[Plum Crazy Rob]

Looking good.

With the bonkers price increases on the Solar hybrids now up to $2k-2.5k, use cases are getting way tighter...

Curious to see if the $600 mini's shortly become $1200 and/or out of stock, but I would also be even more glad if the tariffs situation is resolved before that.

 

[dopeassjackson]

The same one now has $99 shipping charge.

 

[JoeHam]

The same one now has $99 shipping charge.

But…… they can say they didn’t raise the price

 

[740GLE]

Got my 120v mini split installed this weekend. Off amazon I ordered a glacier and received a costway, this didnt really matter to me. I did the whole install my self. With the mini split and line set cover the total cost was aboit $600. On full cool it will pull 750-800w from my batteries. On full heat is about 900w. Just low enough to run on my current 1200w inverter. This weekend I also added a 4th 235w solar pannel and swapped out my 40a CC to a 80A. Overall the mini split install was prety easy and the cost is prety compatible to a 12kbtu window unit.

The thing I dont really like is the condensor fins have no cover on 2 of the 4 sides. I'm going to change this and put lovers over the unit. In the few short hours I ran it I alreaty found a leaf stuck to it. This outdoor unit is installed under my unskirted cabin so wont get wet or have ice/snow or sun on it.

Thanks to everyone who said to skip the solar mini split. Cut the cost in more than half and I would have been running the generator anyway this cloudy weekend.

What’s the square footage of the camp?

 

[dopeassjackson]

What’s the square footage of the camp?

It's a bit hard to calculate with the gambrel roof 2nd story. Bit my best calculations figure about 750sqft if it had 8' ceilings every where. However it does have 4in foam with r21 over that in the roof, r21 fiberglass walls and 4in foam in the floor. Since it's a weekend cabin the insulation matters less because you have a ton of thermal mass to heat/cool when arriving.

 

[740GLE]

It's a bit hard to calculate with the gambrel roof 2nd story. Bit my best calculations figure about 750sqft if it had 8' ceilings every where. However it does have 4in foam with r21 over that in the roof, r21 fiberglass walls and 4in foam in the floor. Since it's a weekend cabin the insulation matters less because you have a ton of thermal mass to heat/cool when arriving.

Ours is about the same square footage, but with an open loft second floor.

That’s an impressive amount of insulation for a cabin.

We only have 3” spray foam on the roof and second floor and 2” on the first floor walls.

We’ve never spent much time in the colder months due to not wanting to deal with frozen water. So it’s mainly to keep the sun from turning the second floor into sauna.

My hope is a 12k mini split will be able to keep the second floor more comfortable in peak summer, don’t need to keep it constant 72, more of knock 85 down to 78 or something.

 

[dopeassjackson]

Ours is about the same square footage, but with an open loft second floor.

That’s an impressive amount of insulation for a cabin.

We only have 3” spray foam on the roof and second floor and 2” on the first floor walls.

We’ve never spent much time in the colder months due to not wanting to deal with frozen water. So it’s mainly to keep the sun from turning the second floor into sauna.

My hope is a 12k mini split will be able to keep the second floor more comfortable in peak summer, don’t need to keep it constant 72, more of knock 85 down to 78 or something.

Ours is about the same square footage, but with an open loft second floor.

That’s an impressive amount of insulation for a cabin.

We only have 3” spray foam on the roof and second floor and 2” on the first floor walls.

We’ve never spent much time in the colder months due to not wanting to deal with frozen water. So it’s mainly to keep the sun from turning the second floor into sauna.

My hope is a 12k mini split will be able to keep the second floor more comfortable in peak summer, don’t need to keep it constant 72, more of knock 85 down to 78 or something.

Ours kind of has an open loft but it's a 38in opening. I have a 120v ceiling fan with DC motor that really helps move the air and takes little power. I hope to keep the whole cabin at 73* this summer. 78* would be prety disappointing to me. But the humidity here can be killer.

 

[740GLE]

Ours kind of has an open loft but it's a 38in opening. I have a 120v ceiling fan with DC motor that really helps move the air and takes little power. I hope to keep the whole cabin at 73* this summer. 78* would be prety disappointing to me. But the humidity here can be killer.

Here’s our loft area, the studs is the kids room, which will house the Minisplit, so that will be plenty cold.

I have two ceiling fans I’ll be installing before the mini split. There’s no roof vents so it’s a heat dome. Between the fans and the mini split I hope enough air is moving around to be comfortable. Anything will be better than it has been the past couple summers.

The night temps usually drop so first floor with windows open cool down decently, but humidity can be bad.

 

[ksmithaz1]

I'm weighing all options and a total rebuild of my working solar system isnt really an option.

If the needs are short term you want a short-term solution. But you left out the effort aspect completely, and the cost to rip and replace if the solution needs to extend, and your ROI. I mean you don't have to have an A/C at all, or, if it's really about the money, get a $600 mini-split and a $400 generator, skip all the panel hassle. Better yet, spend the extra money for the hybrid abortion on a larger propane based genny, and a bigger tank.

Everyone seems to think you can get a hybrid 1.5T unit that needs around 1500 watts peak, hook up 3x500 watt panels and get free HVAC all day and all night. Unfortunately you will come to a rude awakening as this will not perform as expected since you are going to need twice that many panels if you expect it to even work most of the time without the grid. Further, the sun goes down at 17:30 or before to the point you can't run the thing off that 3000W of panels anymore.

You have to have the grid as a buffer for when the sun is not shining. This grid will have to be able to absorb the max (here comes the dreaded) DEMAND the unit is capable of requesting every time a cloud comes by, or there is insufficient sunlight. Further the ROI for all this is abysmal, unless your grid power is really expensive, say $0.50/kwh or more. Then any panels simply reduce the cost of running the unit during the 6-8 hour sun window, when it's not cloudy. It only solves a narrow extreme edge case, and will end up being often useless, when it's hot and you have no sun.

I'd do like my grandparents would have done . . . without.

 

[dopeassjackson]

View attachment 295433
Here’s our loft area, the studs is the kids room, which will house the Minisplit, so that will be plenty cold.

I have two ceiling fans I’ll be installing before the mini split. There’s no roof vents so it’s a heat dome. Between the fans and the mini split I hope enough air is moving around to be comfortable. Anything will be better than it has been the past couple summers.

The night temps usually drop so first floor with windows open cool down decently, but humidity can be bad.

This is almost exactly how are upstairs is but a gambrel roof and a wall down the center for a room on the right side. We have a $45 wall mounted fan in that room to blow some air out. It works well, runs all night and keeps things off the floor. Important in a small space. I can keep a 2*f different between that upstairs room and the downstairs with the ceiling fan on low. I really like our DC ceiling fan. Its quiet, energy efficient and moves quite a bit of air.

 

[Plum Crazy Rob]

hybrid abortion...ROI..is abysmal, unless your grid power is really expensive, say $0.50/kwh or more

Ok, apologies to OP for some thread jacking - everyone, including ME, steered him AWAY from the hybrid for his application, he's installed a conventional unit and it looks like it's working well - but I feel I need to address this above...

@ksmithaz1, I find your posts typically informative and enjoyable - along with several others that habitually kick the hybrid mini split - if you want to say it's dumb and you don't like it, fine - but your ROI theory is lacking

I spent $4500 (after tax credits) setting up 4 tons of Solar hybrids - a 24k BTU unit on 1st floor, and 2 12k BTU units in 2 of my 4 2nd floor bedrooms. 2500sq ft house normally on 4 ton Geothermal HP. Yes it's 6160W of panels (385W x 16 on EG4 Brightmount ground mounts)- a "lot of panels", but I don't obsess about that anymore than the 7 cars, a boat, tractor, and bulldozer in my garage I am not "utilizing" to the maximum. Panels are so cheap now we build fences, pergolas, and now garage doors with them (lol).

Results are below, AFTER Solar hybrids on the Left, BEFORE on the right. I rescaled the left / y-axis to agree with each other. As many here know, Jan '24 was a giant sunless turd...review the "my batteries are dead, switched to Grid" threads here at that time.

Annual savings is 7 MWh. I pay $130/MWh (0.13/KWh) = $910

$4500/910 = 4.95 yrs ROI payback.

But wait...there's more. Ive been a cheap bastard the whole time. My original annual usage of 17MWh was with the thermostat set 58F Winter / 78F Summer days and 68F nights.

Now, i overdrive the units / use a free thermal air battery / comfort is much improved - as many here do with mini splits, conventional or other - typically 80F Winter Day, 65F Summer day, 68F Winter nights, 62F Summer nights.

I feel pretty comfortable then in claiming
*** 3 Yrs ROI payback*** apples to apples had i run the Geothermal to the same temps.

 

[Plum Crazy Rob]

As far as Nights, ummm..
Well, depending on Winter/Summer it's already Hot or Cold conditioned air, which running the Bedroom / 2nd floor Hybrids 100% on grid typically results in several hours of coasting, then 1-2 KWh per night. Typical worst months, January for Heat, and June for Cool, are sampled below on a 12k unit, along with coasting at 160W. Keep in mind other months, usage on Grid is less.

 

[Plum Crazy Rob]

Is a Solar Hybrid mini split your gateway to unplugging from the Grid, well No, not even close. But, it IS a cheap and simple way to knock out your number one power use for many, HVAC.


You could then dovetail this with a much SMALLER Solar system panels/batteries/inverter to knock out the rest of your usage or add redundant capabilities.