diy solar

diy solar

Heat tiny home with mini split year round in cloudy oregon?

oregonsun

New Member
Joined
Aug 18, 2021
Messages
105
I have found many threads on mini splits running on solar used for cooling, how about for heating in worst case scenario oregon cloudy winter weather?

I have pioneer 12kbtu 115v 20 seer 10 hspf mini split, not yet installed., (low ambient unit, supposed to work in lower outdoor temps)

Current solar setup: Completely off grid

Growatt 3000es 48v
10kw amperetime lipo4 (4x 12v200ah)
10x 440w solarever panels

Room to heat is only 18x16x9ft, not yet insulated (house built in 1870) but will do what I can.

Location: Coos Bay, Oregon

Just guessing here, I expect I'm going to need to at least double my batteries and perhaps double my solar panels to get close to pulling this off because solar input here is greatly reduced in heavily cloudy winter weather much of the time. Most of the year it's above 45f here, so it's not extreme cold and for the worst days I can heat with propane, but I'm trying to get off of the skyrocketing costs of propane as much as possible.

Does anyone here have any experience on heating with a mini split like this in my poor weather conditions, to confirm if this is even going to work or if I'm just headed for failure?
 
Last edited:
I have found many threads on mini splits running on solar used for cooling, how about for heating in worst case scenario oregon cloudy winter weather?

I have pioneer 12kbtu 115v 20 seer 10 hspf mini split, not yet installed., (low ambient unit, supposed to work in lower outdoor temps)

Current solar setup: Completely off grid

Growatt 3000es 48v
10kw amperetime lipo4 (4x 12v200ah)
10x 440w solarever panels

Room to heat is only 18x16x9ft, not yet insulated (house built in 1870) but will do what I can.

Location: Coos Bay, Oregon

Just guessing here, I expect I'm going to need to at least double my batteries and perhaps double my solar panels to get close to pulling this off because solar input here is greatly reduced in heavily cloudy winter weather much of the time. Most of the year it's above 45f here, so it's not extreme cold and for the worst days I can heat with propane, but I'm trying to get off of the skyrocketing costs of propane as much as possible.

Does anyone here have any experience on heating with a mini split like this in my poor weather conditions, to confirm if this is even going to work or if I'm just headed for failure?
It's math. Expect failure and enjoy the journey.

What are your panels currently producing?

The other factor isn't so much the clouds but the length the winter days. You're asking for 16 hours worth of reserve to be replenished in 8 hours.

Panels are cheap. I do ok with clouds in wa state but rain kills output to maybe 1-3% of nameplate. Lucky to get .2kwh on rainy winter day out of a 2400 watt array.
 
I have found many threads on mini splits running on solar used for cooling, how about for heating in worst case scenario oregon cloudy winter weather?

I have pioneer 12kbtu 115v 20 seer 10 hspf mini split, not yet installed., (low ambient unit, supposed to work in lower outdoor temps)
I have a 9000BTU Senville - https://senville.com/9000-btu-mini-split-air-conditioner-senl-09cd/ (20.5 SEER) in my 7 x 14 trailer - 100sq ft. The trailer has has R5 (1" foam) all around. In moderate temps (low 40 / hi 90) it takes about 6kwh/24hrs to keep 75F/24C.

Current solar setup: Completely off grid

Growatt 3000es 48v
10kw amperetime lipo4 (4x 12v200ah)
10x 440w solarever panels
That's 4.4kw PV. I'm in Southern Oregon (Medford) with 13kw PV. You can do PVWatts https://pvwatts.nrel.gov/pvwatts.php for your location but by extrapolation based on my location that would be aprox.....
- 680kwh/month in summer
- 170kwh/month in winter (Dec/Jan/Feb) Note: Dec 2021 was an anomaly and sooooo rainy it would be 85kwh/month by extrapolation but Jan/Feb were higher than normal.

So that's (680kwh/31days) 22kwh/day in summer and (170kwh/31days) 5.5kwh in winter.

Room to heat is only 18x16x9ft, not yet insulated (house built in 1870) but will do what I can.
That's 288sq ft = 3 x my trailer and hopefully better insulation so let's say it's 12kwh/day for moderate temps.

For spring/summer/fall - you're within range based on extrapolations from my experiments :)
For winter - you're going to be short 5kwh/day. So maybe lower to 60F/15C or stay warm 1/2 the day - maybe during the day.

Location: Coos Bay, Oregon

Just guessing here, I expect I'm going to need to at least double my batteries and perhaps double my solar panels to get close to pulling this off because solar
Battery wise, again by extrapolation with my system, you'll need aprox 14kwh battery bank @ 80% DOD to be able to consume all the 4.4kw PV will produce - e.g. keep things powered thru the night till morning sun is enough to kick in.

You're 10kwh battery in range and may work for you. I'd try it and expand later if you need.

input here is greatly reduced in heavily cloudy winter weather much of the time. Most of the year it's above 45f here, so it's not extreme cold
Same for me and when I gave the 12kwh/day I'm talking 40F low. But if you're like me, it can go to middle 30sF for a few weeks and occasional low of 25F. If you try to maintain the same house temp at 30F ambient vs 45F ambient it takes significantly more power.

and for the worst days I can heat with propane, but I'm trying to get off of the skyrocketing costs of propane as much as possible
Does anyone here have any experience on heating with a mini split like this in my poor weather conditions, to confirm if this is even going to work or if I'm just headed for failure?
The heat pump will work just fine (I would trust the low temp specs of your unit) but it's a matter of power. I did winter camping with 20F outside and the 9000BTU mini-split worked fine... trailer was 75F... but it took twice the power it does at 45F. When I lower the inside temp to 60F with <30F ambient the power cuts in 1/2 and is back to the 6kwh/24hr range.

Insulation makes a large difference. I'll be following this thread and would love to hear your experience as you see how things work for you.
 
Last edited:
I didn’t do the math. But with cloudy days and short sun hours you are likely going to want four times or more of the panel wattage you might think you need, and plan for a generator.
With the cost of fossil heat, however, the ROI on panels might be somewhat short on the grand scale of things.

The one part that will hurt is battery cost.
 
I don't know about Coos Bay, but if it's anything like my place figure about 3% panel effectiveness once those clouds and rain roll in. You're going to really want to plan for some kind of generator setup to recharge the batteries. Fortunately the Charging Amps listed for the AIO's are battery amps, NOT generator amps so usually something in the 2-3000w range is plenty.
 
In an area that solar is so difficult to produce I wouldn’t consider using a AOI because of the self consumption. I may even consider a battery voltage heat pump ( leaving the inverter turned off some of the time). My Growatt consumption is 1.5 kw per day. It consumes this while producing AC watts or idle. So be sure to allow for it.
 
Last edited:
In an area that solar is so difficult to produce I wouldn’t consider using a AOI because of the self consumption
This is true. I’m currently running a 1012LV-MK. I’ve measured idle consumption more than several times because it seems to vary for unexplained reasons. The consistently close is 2.8-3.0A. Just now 2.98A at 14.3VDC aka 45W which is essentially 1kW a day.
The Giandel 1200W pure sine inverter was generally 25w (or was it 18??!) and the not-connected Reliable / QZRELB 2000W was 11W idle.
For me it’s not production that’s an issue for idle consumption, it’s overnight and cloudy days. I was better performing when running the Epever but it had “the equalizing dropouts” I was trying to get away from.
I love that little AIO but it does make a difference when the sun goes down.
 
It's math. Expect failure and enjoy the journey.

What are your panels currently producing?

The other factor isn't so much the clouds but the length the winter days. You're asking for 16 hours worth of reserve to be replenished in 8 hours.

Panels are cheap. I do ok with clouds in wa state but rain kills output to maybe 1-3% of nameplate. Lucky to get .2kwh on rainy winter day out of a 2400 watt array.

I don't have my panels installed yet, (I only have 4 connected atm just laying on the ground) and they're shaded by the house until after noon.
4 panels shaded half the day in the summer is enough to get me 2 to 5kw for the day.

Yesterday was a fairly dark cloudy day, and 4 panels gave me 2.7kw, but that's way more than winter sun which made them barely able to cover the idle consumption of the growatt. I was quite surprised at how high the idle consumption was, lesson learned. I will have to figure something else out other than the growatt for winter here, you guys are right the idle consumption is really high.

Last winter was brutal with low light, my solar system was basically just a battery for my gas generators to charge, I have four gas generators, but in those worst conditions I will just switch to propane heat.

If I have to get through 2-3 months on propane heat that's better than 12 months on propane, I guess, and seems cheaper to heat with propane directly than to try to run on generator charging the batteries.

If it weren't for the cost of propane tripling here lately I'd be ok, but it's just painful flushing that money down the toilet. When I started here propane was $1.60, then it hit a high of $3.60, now it's down to $3 per gallon.

I have a couple 5kw diesel parking heaters I could try, also not installed yet, not sure if those would be any cheaper to run than propane.

What solar charge controller and inverter should I be looking at for lower idle consumption? 3kw inverter seems like a nice size for me.
 
I don't have my panels installed yet, (I only have 4 connected atm just laying on the ground) and they're shaded by the house until after noon.
4 panels shaded half the day in the summer is enough to get me 2 to 5kw for the day.

Yesterday was a fairly dark cloudy day, and 4 panels gave me 2.7kw, but that's way more than winter sun which made them barely able to cover the idle consumption of the growatt. I was quite surprised at how high the idle consumption was, lesson learned. I will have to figure something else out other than the growatt for winter here, you guys are right the idle consumption is really high.

Last winter was brutal with low light, my solar system was basically just a battery for my gas generators to charge, I have four gas generators, but in those worst conditions I will just switch to propane heat.

If I have to get through 2-3 months on propane heat that's better than 12 months on propane, I guess, and seems cheaper to heat with propane directly than to try to run on generator charging the batteries.

If it weren't for the cost of propane tripling here lately I'd be ok, but it's just painful flushing that money down the toilet. When I started here propane was $1.60, then it hit a high of $3.60, now it's down to $3 per gallon.

I have a couple 5kw diesel parking heaters I could try, also not installed yet, not sure if those would be any cheaper to run than propane.

What solar charge controller and inverter should I be looking at for lower idle consumption? 3kw inverter seems like a nice size for me.
My AIMS 3kw draws like 12 watts @ idle.

This is where you need to get fancy. You need to get your fab skills up and going so you can recover heat from your generator and use that to heat the house while you're using it to charge the batteries.

With a mini split heat pump, you could start by simply passing the exhaust and cooling air into the intake of the condenser.
 
I have a couple 5kw diesel parking heaters I could try, also not installed yet, not sure if those would be any cheaper to run than propane.
I have a couple of those at my camp and what I can say from experience is that they kick ass! If your insulation is halfway decent you're looking at 3-4 gallons a week of diesel. The fact that they run on 12v DC makes them very solar friendly as well.

About the only downside to them is that when they're idling or running under low load (because they never shut off, just slow down the fuel) they tend to get gummed/sooted up inside and need to be cleaned. After a week of idling I open mine up and clean them out so they're all ready to fire off next time I come to camp, although they have run for 2 weeks straight without a cleaning before (and it showed inside!).

If you're interested, feel free to PM me and I'll send you the step-by-step I put together for how to open them up and clean them and some tips & tricks to keeping them happy. If you have ductwork in the house already you can just pipe them right in and you're good to go.
 

Attachments

  • back diesel heater.jpg
    back diesel heater.jpg
    200.4 KB · Views: 8
  • inside temp.jpg
    inside temp.jpg
    131.1 KB · Views: 8
  • outside temp.jpg
    outside temp.jpg
    173.1 KB · Views: 8
Last edited:
I have a couple of those at my camp and what I can say from experience is that they kick ass! If your insulation is halfway decent you're looking at 3-4 gallons a week of diesel. The fact that they run on 12v DC makes them very solar friendly as well.

About the only downside to them is that when they're idling or running under low load (because they never shut off, just slow down the fuel) they tend to get gummed/sooted up inside and need to be cleaned. After a week of idling I open mine up and clean them out so they're all ready to fire off next time I come to camp, although they have run for 2 weeks straight without a cleaning before (and it showed inside!).

If you're interested, feel free to PM me and I'll send you the step-by-step I put together for how to open them up and clean them and some tips & tricks to keeping them happy. If you have ductwork in the house already you can just pipe them right in and you're good to go.

Thanks
I have a diesel parking heater in my stepvan conversion, and I lived in that for a year while looking for a new house while I kept getting outbid or beaten to the punch on house after house after house.

I agree they are awesome, but I wasn't tracking the cost of use at the time so I don't know if it will be cheaper than propane for the house or not. I guess it's time to install one and try it.

I only had to take mine apart to clean it once in the year I used it, that was before I found tips online to be sure to run it on high every couple weeks to burn off the soot for like an hour. That made a huge difference. If you regularly run it on high before the soot stops it from working it's a lot easier it sort of cleans itself out. Not completely, but enough to avoid tearing it apart so often.

As for insulation/ductwork my house was built in 1870, they didn't know what insulation or ductwork was, nor drywall, and this house doesn't even have lath and plaster it was built like a barn and I'm looking at having to tear off siding and open up walls to do anything about it. The floor will be easy to insulate, everything else looks like a nightmare to do if not impossible. There is no way to insulate my ceiling without complete demolition, but I have an unused second floor maybe I can throw some foam board on the floor.

Next winter I may just camp out in my stepvan conversion if it's as bad as this winter was, i have insulated that and it's pretty cozy in there just with the diesel heater on the lowest setting except when the weather drops below freezing. I put in 1.5" white foam with the foil backing in there, and have another 1" layer yet to be added on top of it.

I plan to mount the solar panels I have now on the stepvan to completely cover the roof, so they will do double duty for home and travel. I can fit 8 of them on the roof with a bit of overhang front and rear.

Too many projects over here and poor health getting in my way of getting them done. I've had covid twice now and the last time was a 3 month battle hoping not to die.
 
You are better off with small and efficient wood stove. Make sure to recapture exhaust heat to avoid dumping useful energy to the outside. 1 pound of dry wood produces 2.5 kWh of heat. With an air source heat pump you may end up with coefficient of performance (COP) of 3 with mild temps and down to 1.5 - 2 with cold temps. That means in cold weather you would need 1 - 1.5 kWh of electricity to make same heat as 1 lb of firewood with losses of both woodstove and AC inverter accounted.

Consider building water heated insulated concrete floor (radiant heat floor) powered by air to water heat pump. COP of that can get into 3 - 4 range and 5+ range with ground source heat pump. Another benefit is circulating warm water heated by exhaust heat of the wood stove and large heat store that concrete slab would offer.
 
Last edited:
My AIMS 3kw draws like 12 watts @ idle.

This is where you need to get fancy. You need to get your fab skills up and going so you can recover heat from your generator and use that to heat the house while you're using it to charge the batteries.

With a mini split heat pump, you could start by simply passing the exhaust and cooling air into the intake of the condenser.
!2 watts sounds amazing, thanks, I will definitely check that out.

The plan is to not use the generators at all if I don't have to. I'll be using propane or diesel for heat when I can only get enough solar for the basic necessities of life.

To me the basic necessities of life are a couple LED lights, microwave and fridge and tv, and high speed internet modem and wifi router and laptop and smart plugs, phone charger, security camera, and two class d aiyima audio amps which I drive four tower speakers with. Can't live without my big ass tower speakers, I'm happy I found those a07 amps that I can run all day long on solar. My daily power needs are only around 2.5kw for all of that, not counting any heating or cooling or cooking.
 
You are better off with small and efficient wood stove. Make sure to recapture exhaust heat to avoid dumping useful energy to the outside. 1 pound of dry wood produces 2.5 kWh of heat. With an air source heat pump you may end up with coefficient of performance (COP) of 3 with mild temps and down to 1.5 - 2 with cold temps. That means in cold weather you would need 1 - 1.5 kWh of electricity to make same heat as 1 lb of firewood with losses of both woodstove and AC inverter accounted.

Consider building water heated insulated concrete floor powered by air to water heat pump. COP of that can get into 3 - 4 range and 5+ range with ground source heat pump. Another benefit is circulating warm water heated by exhaust heat of the wood stove and large heat store that concrete slab would offer.
I actually bought a morson squirrel wood stove to put in, but I have no chimney it was torn out before I bought the house and this is a two story house with a hugely tall attic on top of that, so having a bit of trouble figuring out how to make that work.

I call this my tiny home because I'm just living in one room atm, but it's actually a 1500sf two story farmhouse with an attic so huge it could be a whole third floor living space.

Nobody will install the stove though, since it's not epa approved or whatever.

They say I can only install a pellet stove now, or maybe a crazy expensive new wood stove that is designed for new epa requirements. I was quoted over $5k for the cheapest pellet stove install, probably more than half of that was the massive cost of the three story insulated chimney I'd need.

I can't just strap a new chimney to the side of the house myself either, I'm smack dab in the middle of town and that would attract the attention of inspectors is my guess. I can't have inspectors out here because they'd freak about my solar setup and how all the wiring in the house was destroyed by tweakers before I bought the place. It's a huge fixer house in need of just about everything. I was told before I bought the house. that it wasn't economically repairable and that's proven itself to be true, I have to do all the work myself just to make it even worth doing financially. I only paid $40k for the house, in an area where if it was in good shape it would cost $240k. No houses here are ever that cheap, nobody else was willing to even take this 1870 pile of rotting wood and lead paint project on. The city was going to demolish this house before I bought it, but they found the cost of demolition was going to be too high so they sold it instead.
 
Last edited:
In this case go with diesel or propane heater whichever has cheapest fuel. Residential propane is $3/gal and has 24.6 kWh of energy. You can either heat directly with propane for 12.2 cents per kWht or get creative and burn it in piston engine generator to get 3.6 kWh electrical and 21 kWh of heat for each gallon. Do you have electricity service at this house? What are the rates and is there a TOU plan available?
 
In this case go with diesel or propane heater whichever has cheapest fuel. Residential propane is $3/gal and has 24.6 kWh of energy. You can either heat directly with propane for 12.2 cents per kWht or get creative and burn it in piston engine generator to get 3.6 kWh electrical and 21 kWh of heat for each gallon. Do you have electricity service at this house? What are the rates and is there a TOU plan available?
The house had electricity, but the main line coming from the power company pole was removed completely after the house was abandoned, then squatted in and vandalized.

Before I can get electric reconnected I have to completely redo all the wiring, all the outlets, all the switches, and replace the entire breaker box, and I'm going to have to do all of that myself in order to make it economically feasible at all. I had electricians out here for bids and they laughed at me.

And before I do that I'm going to have to remedy about dozen other issues that prevent me from inviting any inspectors out here yet.

Then after all that, it's probably going to cost like another $5k just to get the line replaced from the pole to the breaker box. I haven't gotten a quote for that yet, that's just my guess.

Power here would be relatively cheap like .12c per kwh, if not for all the things that need to be fixed first and preventing me from getting to it, including my health.
 
I actually bought a morson squirrel wood stove to put in, but I have no chimney it was torn out before I bought the house and this is a two story house with a hugely tall attic on top of that, so having a bit of trouble figuring out how to make that work.

I call this my tiny home because I'm just living in one room atm, but it's actually a 1500sf two story farmhouse with an attic so huge it could be a whole third floor living space.

Nobody will install the stove though, since it's not epa approved or whatever.

They say I can only install a pellet stove now, or maybe a crazy expensive new wood stove that is designed for new epa requirements. I was quoted over $5k for the cheapest pellet stove install, probably more than half of that was the massive cost of the three story insulated chimney I'd need.

I can't just strap a new chimney to the side of the house myself either, I'm smack dab in the middle of town and that would attract the attention of inspectors is my guess. I can't have inspectors out here because they'd freak about my solar setup and how all the wiring in the house was destroyed by tweakers before I bought the place. It's a huge fixer house in need of just about everything. I was told before I bought the house. that it wasn't economically repairable and that's proven itself to be true, I have to do all the work myself just to make it even worth doing financially. I only paid $40k for the house, in an area where if it was in good shape it would cost $240k. No houses here are ever that cheap, nobody else was willing to even take this 1870 pile of rotting wood and lead paint project on. The city was going to demolish this house before I bought it, but they found the cost of demolition was going to be too high so they sold it instead.
Just use grid power then.

Or can you not hook up to it cuz code?

Edit: my bad. Simultaneously posted this when you made the post above answering the question
 
Last edited:
I am surprised you can get away with living there. A house without utility service would quickly get condemned here. I guess your best bet is flying under the radar for as long as you can and use 20 gal propane tanks either delivered or drive them to refill at local gas supply company.
 
I am surprised you can get away with living there. A house without utility service would quickly get condemned here. I guess your best bet is flying under the radar for as long as you can and use 20 gal propane tanks either delivered or drive them to refill at local gas supply company.
I am my own utility service and my power is way more reliable than the electric company, but yes flying under the radar for sure, just skimming the ground as I go.
 
Another benefit is circulating warm water heated by exhaust heat of the wood stove and large heat store that concrete slab would offer.
Maybe you do. Most people have no idea how efficient that is.
I’d likely run a firebox coil, however. Been around wood heat and all kinds of things to get more heat out of a woodstove. But you want a hot chimney to cut down on creosote so I’m averse to wood-fire exhaust heat recovery.
 
Last edited:
Back
Top