Energy-conscious/efficient off-grid tiny home setup help

[Tomthumb62]

I have no way to see what everything runs at, unless I get a meter and take all my appliances to a friend's and see how much they pull.

If you skip this, you may end up spending a lot more money than you need to.

If you size your system way too big, that’s expensive.

If you size it too small, you’ll need to upgrade it and that’s expensive, too. Such as, what to do with the equipment that’s now too underpowered and needs to be sold at a loss and past the return window?

Get a DC clamp meter that can measure inrush current, not all of them do this.

 

[E. Cho]

The other way to do this without testing the energy draw of appliances, is to use the maximun energy required for each appliance as per the appliance label, in watts (or converted from stated amps) and the length of time per day that each will be used. # of watts per hour totalled gives you watt hours for the energy audit. Then roughly, this will help size the solar panels to produce what you need and the inverter, charge controller to convert the power into say 3x that for battery storage and then to convert to 110 AC.

The energy audit can be calculated guesses but it's more accurate if it's not. Don't rely on doing it just once either vs over a few or more days.

Unfortunately, in my experience at least, there is a learning curve to all this and so frustration for some of us whose brains are not as logical as maybe an engineer's or an electrician's brain. I've done 2 systems that have been running well, no shocks, no fires and with a few redos for small mistakes. So if I can do it, many others could too. I also forget much of what I have learned after I no longer need it. I also go slow, perhaps too slow but I don't want to make expensive or dangerous mistakes.

Just keep reading and watching videos and asking questions and slowly or quickly things will get figured out.

First do a rough guestimated and or measured audit, let it stew and then review it and do it again and maybe later do it again as you research the other parts of the system.

 

[Daddy Tanuki]

like I suggested earlier, do the rough audit and double it. there is a thing called project creep where your plan is A but you end up with BCDEFG as your plans grew and grew. the power plant for your system must be large enough and robust enough to grow as your project expands.

 

[carbondrewtonium]

like I suggested earlier, do the rough audit and double it. there is a thing called project creep where your plan is A but you end up with BCDEFG as your plans grew and grew. the power plant for your system must be large enough and robust enough to grow as your project expands.

I filled out a rough estimate. Conservative numbers for the things I'll likely use each day. Why are some of the fields coming up with errors? Also, how can I interpret these data to know what size inverter, bank, controller, etc. I need?

 

[Daddy Tanuki]

I filled out a rough estimate. Conservative numbers for the things I'll likely use each day. Why are some of the fields coming up with errors? Also, how can I interpret these data to know what size inverter, bank, controller, etc. I need?

View attachment 159085View attachment 159086

looks to me like you used the filled in sample, use the tab listed as stationary ac loads instead and retry it. chances are one of the fields is missing an expression and thats what is fouling it up. so use the tab listed as "stationary AC loads" and try it again.

also if it does not have a motor, and is simply an element, or light it has no surge load. you have the kettle as surging to 3000 if it is a 1200 watt resistive load their is no surge above the 1200 watts. compressors, motors etc have a surge rating as the motor goes LRA to spinning. hence a surge.

 

[carbondrewtonium]

looks to me like you used the filled in sample, use the tab listed as stationary ac loads instead and retry it. chances are one of the fields is missing an expression and thats what is fouling it up. so use the tab listed as "stationary AC loads" and try it again.

also if it does not have a motor, and is simply an element, or light it has no surge load. you have the kettle as surging to 3000 if it is a 1200 watt resistive load their is no surge above the 1200 watts. compressors, motors etc have a surge rating as the motor goes LRA to spinning. hence a surge.

Ah, I had filled out the mobile tab instead of stationary. I filled in the stationary with the likely must-have daily items:

 

[E. Cho]

What size of chest freezer? My 7.2 cu ft Danby freezer only uses 50-60 watts running every 15-20 minutes for about 5 minutes (0 watts not running) and has a guesstimated surge of abut 600 watts (viewed as a spike on my Poniie energy meter when I watched it kick on. I don't yet have a clamp meter capable of measuring in rush DC current but it's on my tool list when I can afford it.) By my 7.2 cu ft. freezer's smart plug energy monitor app, it shows the average power consumption over the last 6 months at 11.40 KWh per month. Your chest freezer at 400 watts running watts seems 10x higher than mine? So, listing these appliances by using an Energy Monitor device or even a smart plug with energy monitoring, will help you size your system more accurately so you buy right the first time.

I don't have a mini split but after looking at half a dozen YouTube videos to learn something about them, I have yet to see one around the same size as your Senville mentioned that has a surge of 4800 watts. That seems extremely excessive but if it is accurate, then you need to find an inverter than can in fact handle a 4800 watt surge, (plus whatever else may be running at the time eg: 4800 watts plus 1200 watt coffee maker? plus laptop, plus LED lights?) However, from the videos, the Senville seems to maybe have a starting surge of 1,000 watts and about 950 watts running until it reaches it's target temperature settings and then only 50-100 watts while maintaining it's settings and below 10 watts in idle.

Will Prowse EG4 Mini-Split Video

The one video on the Senville mini split says that he has a 5 KWh (5,000 Watt) battery that can run the mini split for 24 hours before depleting the battery. If you wanted an extra day of poor solar production, then you may want to size your battery to be 10+ KWh. It's not that linear though, as you will also have other appliances to use and or you could really scrimp on your power consumption to try to get the watts used more sporadically in your personal survivor mode. Heating / Cooling are your biggest power draws unless you super insulate your Tiny Home (which would be desirable anyway, if possible).

Senville Mini-Split Energy Use Video
https://www.youtube.com/watch?v=cF-7XkXP7RU

Presently it's cloudy. Cloudy day = Poor Solar. My 2280 Watt array at 10 a.m. and cloudy is only producing 150 watts or roughly just 6.7% of it's 2280 capacity. But I am also not running any high power demand loads, basically only 70 watts, so I have the remaining solar of 80 watts charging the battery. If I had a 720 mini split running at 720 watts, then I would be drawing down my battery at 570 watts continuously (720-150 watts) when my solar production is only 150 watts. Or if you used a Solar Panel DC capable mini split such as the EG4, then your panels could not run the mini split until your panels were receiving 720+ watts of sunshine, so your batteries would have to help make up the difference.

So if you choose not to accurately measure or find info of appliances like yours accurately measured, such as on maybe YouTube, then by guessing you may need:

Solar Panels: 6 x 430 Watts = Okay minimum

Inverter: 4000 Watt+ inverter to handle your guessed 4800 surge (BE careful of inverter HYPE as some inverters over hype their capabilities and most don't even mention what type of "motors" or in rush current they handle. A good quality Low Frequency inverter is recommended or get the reseller or manufacturer to comment on your appliances OR ACCURATELY MEASURE your appliances in use).

Battery: 5 Kw LiFePO4 capacity at minimum, 10-15 KWhr desirable.

Solar Charge Controller: Would need to be sized based on how you wire your solar panels. Eg: I have 6 x 380 watt panels that are wired as 3S (3 in Series) + 2P (2 in Parallel) - creates a maximum of 79.2 Charging Amps at 28.8 degrees Celsius and 135 Volts (VOC) at a max low of -35 degrees Celsius, so I sized my MPPT Solar Charger Controller to be: 150 Volt / 85 Amps Victron.

My 24 volt system would easily be able to handle your loads, but my battery capacity is too low for overnight or cloudy or cloudy winter days as there isn't enough reserve capacity at 100 AHrs to run the mini split for over night or 24 hours without seriously running it down but could handle your loads when it were 100% sunny. It also depends on how hard the mini split has to work to provide heating and cooling and that is based on the ambient temperatures and the insulation of the area being heated or cooled. So a well insulated space may not require a really large capacity battery and not every day either.

Inverter: 4000 Watt Xantrex (20+ years old - 95% Efficient, 16 Watts idle power use (on 24/7)
Solar Charge Controller: 150V/85 Amp Victron MPPT
Battery: 100 AHr 24Volt LiFePO4 Battery with an Active Balancer BMS (you would need 5-10x this for 24 hour mini split use and for cloudy days + a backup fossil fuel generator like a 2000 watt Honda inverter gasoline generator).
6 x 380 Watt BiFacial Solar Panels
(Plus cables, lugs, bus bars, DC breakers, DC breaker boxes, DC Disconnects, Battery Cable Fuses, Battery Monitoring, plus build tools)

A 48 Volt system would be helpful but research the inverter for the minimum energy use (some call it parasitic load), some All in One units use 70 watts just to be on. Some inverters also don't like to be turned On/Off on a continuous basis.

You may be able to get by with a smaller inverter than 4,000 watts depending on the in rush current of your loads and or how many appliances you want to run at the same time. But personally, I would not go lower based on my usage and I only have minimal needs but my inverter seems to handle everything with ease.

You have enough solar panels to recharge a 5-10 KWhr battery and they will handle the loads you list. You will need a good inverter able to handle your highest surge rating plus any other loads in use and you will need a good MPPT charge controller that will control the volts and amps from the solar panels and at the coldest sunny day in your area.

As the saying goes: "Buy Once, Cry Once". Anyway, hope this food for thought. If you can more accurately measure your loads, list the appliances and useage times, then we can more accurately give you options vs. just guessing.

 

[carbondrewtonium]

What size of chest freezer? My 7.2 cu ft Danby freezer only uses 50-60 watts running every 15-20 minutes for about 5 minutes (0 watts not running) and has a guesstimated surge of abut 600 watts (viewed as a spike on my Poniie energy meter when I watched it kick on. I don't yet have a clamp meter capable of measuring in rush current but it's on my tool list when I can afford it. By the freezer's smart plug energy monitor app, it shows power consumption on average over the last 6 months at 11.40 KWh per month. Your chest freezer at 400 watts running watts seems 10x higher than mine? So trying these appliances out with an Energy Monitor device or even a smart plug with energy monitoring will help you size your system.

I don't have a mini split but after looking at half a dozen YouTube videos to learn something about them, I have yet to see one around the same size as your Senville mentioned that has a surge of 4800 watts. That seems extremely excessive but if it is accurate, then you need to find an inverter than can in fact handle a 4800 watt surge, (plus whatever else may be running at the time eg: 4800 watts plus 1200 watt coffee maker? plus laptop, plus LED lights?) However, from the videos, the Senville seems to maybe have a starting surge of 1,000 watts and about 950 watts running until it reaches it's target temperature settings and then only 50-100 watts while maintaining it's settings and below 10 watts in idle.

The one video on the Senville mini split says that he has a 5 KWh (5,000 Watt) battery that can run the mini split for 24 hours before depleting the battery. If you wanted an extra day of poor solar production, then you may want to size your battery to be 10+ KWh. It's not that linear though, as you will also have other appliances to use and or you could really scrimp on your power consumption to try to get the watts used more sporadically in your personal survivor mode. Heating / Cooling are your biggest power draws unless you super insulate your Tiny Home (which would be desirable anyway, if possible).

Will Prowse EG4 Mini-Split Video

Senville Mini-Split Energy Use Video
https://www.youtube.com/watch?v=cF-7XkXP7RU

Presently it's cloudy. Cloudy day = Poor Solar. My 2280 Watt array at 10 a.m. and cloudy is only producing 150 watts or roughly just 6.7% of it's 2280 capacity. But I am also not running any high power demand loads, basically only 70 watts, so I have the remaining solar of 80 watts charging the battery. If I had a 720 mini split running at 720 watts, then I would be drawing down my battery at 570 watts continuously (720-150 watts) when my solar production is only 150 watts. Or if you used a Solar Panel DC capable mini split such as the EG4, then your panels could not run the mini split until your panels were receiving 720+ watts of sunshine, so your batteries would have to help make up the difference.

So if you choose not to accurately measure or find info of appliances like yours accurately measured, such as on maybe YouTube, then by guessing you may need:

Solar Panels: 6 x 430 Watts = Okay minimum

Inverter: 4000 Watt+ inverter to handle your guessed 4800 surge (BE careful of inverter HYPE as some inverters over hype their capabilities and most don't even mention what type of "motors" or in rush current they handle. A good quality Low Frequency inverter is recommended or get the reseller or manufacturer to comment on your appliances OR ACCURATELY MEASURE your appliances in use).

Battery: 5 Kw LiFePO4 capacity at minimum, 10-15 KWhr desirable.

Solar Charge Controller: Would need to be sized based on how you wire your solar panels. Eg: I have 6 x 380 watt panels that are wired as 3S (3 in Series) + 2P (2 in Paralllel) - creates a maximum of 79.2 Charging Amps at 28.8 degrees Celcius and 135 Volts (VOC) at a max low of -35 degrees Celcius, so I sized my MPPT Solar Charger Controller to be: 150 Volt / 85 Amps Victron.

My 24 volt system would easily be able to handle your loads, but my battery capacity is too low for overnight or cloudy or cloudy winter days as there isn't enough reserve capacity at 100 AHrs but could handle your loads when it were 100% sunny.

Inverter: 4000 Watt Xantrex (20+ years old - 95% Efficient, 16 Watts idle power use (on 24/7)
Solar Charge Controller: 150V/85 Amp Victron MPPT
Battery: 100 AHr 24Volt LiFePO4 Battery with an Active Balancer BMS (you would need 5-10x this for 24 hour mini split use and for cloudy days + a backup fossil fuel generator like a 2000 watt Honda inverter gasoline generator).
6 x 380 Watt BiFacial Solar Panels
(Plus cables, lugs, bus bars, DC breakers, DC breaker boxes, DC Disconnects, Battery Cable Fuses, Battery Monitoring, plus build tools)

A 48 Volt system would be helpful but research the inverter for the minimum energy use (some call it parasitic load), some All in One units use 70 watts just to be on. Some inverters also don't like to be turned On/Off on a continuous basis.

You may be able to get by with a smaller inverter than 4,000 watts depending on the in rush current of your loads and or how many appliances you want to run at the same time. But personally, I would not go lower based on my usage and I only have minimal needs but my inverter seems to handle everything with ease.

You have enough solar panels to recharge a 5-10 KWhr battery will handle the loads you list. You will need a very good inverter and charge controller. As the saying goes: "Buy Once, Cry Once". Anyway, hope this food for thought.

This is a lot of food for thought. I have to admit that I do not fully grasp parts of it. The numbers I put on my audit are high in some cases because I put the largest number I found while researching online. Just want to be safe. I feel like my seven 405w panels can handle what I need. Everything I’ve read online says 3-5 panels can usually power a mini-split. I have more panels than that, a smaller and more efficient mini-split than average, a better insulated building envelope than average, etc. I bought a refrigerator thermostat for the chest freezer, so it won’t even use as much energy as a chest freezer usually would. Again, I was being conservative with the numbers on my audit.

I feel I need a 48v system in the long run because I would like to get to the point where I can use tools (table saw, chop saw, air compressor) one day. I’m the kind of person that can wait for a sunny day or until enough I energy is banked to use those things. So rather I need to do that or add to my system later, I think will be fine either way for me.

 

[carbondrewtonium]

This is a lot of food for thought. I have to admit that I do not fully grasp parts of it. The numbers I put on my audit are high in some cases because I put the largest number I found while researching online. Just want to be safe. I feel like my seven 405w panels can handle what I need. Everything I’ve read online says 3-5 panels can usually power a mini-split. I have more panels than that, a smaller and more efficient mini-split than average, a better insulated building envelope than average, etc. I bought a refrigerator thermostat for the chest freezer, so it won’t even use as much energy as a chest freezer usually would. Again, I was being conservative with the numbers on my audit.

I feel I need a 48v system in the long run because I would like to get to the point where I can use tools (table saw, chop saw, air compressor) one day. I’m the kind of person that can wait for a sunny day or until enough I energy is banked to use those things. So rather I need to do that or add to my system later, I think will be fine either way for me.

I did research wiring panels in parallel vs series and learned that if I decide to add to my array later, it’s important to try to match the voltage/amps as close as possible. And if they are off a bit, to wire in parallel for optimal results. Here is what my seven panels are:

EDIT: Damnit! I looked at the other panels and there is a mix. Three 405w panels, three 400w, one 395. They all look the exact same though. I thought I was getting a good deal on panels but my ignorance may cost more in the long run. Will it makes sense to still wire these seven together? Or should I sell them and get all panels of the exact same specs? I paid $185 each for these.

 

[E. Cho]

Hopefully someone more knowledgeable than me helps you with your solar panel configuration but my OCD would have me want them all matched and using even numbers like 6 vs 7. I found it stressful enough learning it all this way vs throwing in divergence to have to customize my build.

Your power tool needs will require a really good strong (low frequency) inverter to run inductive motors, more than being 48 volts but I agree 48 volts is a good option.

 

[E. Cho]

Forgot to mention that I also have a 7.2 cu ft freezer using an Inkbird digital thermostat to run as a refrigerator. It uses half of the overall energy that my same freezer does but the same 50-60 watts while running and the same starting surge as the freezer but only runs half as often.

So my 100 AHr / 2.5 KwHr battery and 4 KW inverter runs both no problem.

 

[ungrounded]

Hi. I’ve researched off and on for about a year. I’m running electric in my tiny home now so I am to the point of gathering up a cohesive system to be off-grid. I bought 7 Qcell 405w panels (I’ve been told 7 is a weird number to have, so I may sell one). I have two 12v Chvrge batteries but in researching, I believe I should get one 48v battery (Probably the EG4 I see so much hype about) and sell the two 12v batteries. I plan on getting two of these ground mounts: https://signaturesolar.com/eg4-brig...ck-kit-4-panel-ground-mount-adjustable-angle/
I’ve been told Victron is the way to go off-grid, but have also read good things about Sunny Islands and Outback inverters.
I have not looked into charge controller much because I don’t know what size inverter I need.
Am I wrong that the larger the battery voltage is, the smaller wattage inverter I’ll need?
I gave this thread the title because I want to emphasize I plan to have very efficient appliances and I am doing without some common appliances.
I’ll have a mini split (Senville 9k BTU, 20.5 SEER), (2) portable single induction cooktops, a Breville toaster oven, microwave, range hood, energy recovery ventilator, projector, ceiling fan, lights, outlets. That’s it. No water heater. No clothes dryer. Maybe a portable clothes washer later on. Oh, and I hope to power tools outside. Miter saw, table saw, etc. Maybe a CNC machine in the future.
I have a 100 amp breaker box, if that matters.

Anywho, if I want to ground mount 6 405w panels, what size inverter and controller should I look into that will give me the power I need?

Any wisdom on size, brands, etc. are welcomed and appreciated.

I would keep the 7th panel and connect it to your system. It will cover your system inefficiencies.

 

[ungrounded]

I did research wiring panels in parallel vs series and learned that if I decide to add to my array later, it’s important to try to match the voltage/amps as close as possible. And if they are off a bit, to wire in parallel for optimal results. Here is what my seven panels are:

EDIT: Damnit! I looked at the other panels and there is a mix. Three 405w panels, three 400w, one 395. They all look the exact same though. I thought I was getting a good deal on panels but my ignorance may cost more in the long run. Will it makes sense to still wire these seven together? Or should I sell them and get all panels of the exact same specs? I paid $185

Hopefully someone more knowledgeable than me helps you with your solar panel configuration but my OCD would have me want them all matched and using even numbers like 6 vs 7. I found it stressful enough learning it all this way vs throwing in divergence to have to customize my build.

Your power tool needs will require a really good strong (low frequency) inverter to run inductive motors, more than being 48 volts but I agree 48 volts is a good option.

48v inverter is the voltage supplied to the battery.

 

[MattiFin]

On the high wattage appliances like the mini split, if you have it already, I'd try to do a test at a friend's place (on the grid?) in real time over a real time use as it would seem it's a large energy user and it's real world power requirements might be a big surprise based on a guess? Most appliances that heat or cool air or water can be HUGE energy users and for air, will vary greatly depending on the ambient conditions.

Mini split energy usage would depend so heavily on the specific house and users itself that testing at friends house probably wont give that great results. Here up north our entire 120m2 house would need about 2-3 kWh after really hot (90F) day to cool down from 90F to 77F.