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How big of a solar system do I need for a tiny house?

How Many Panels Do You Need To Power A Tiny House? 15 solar panels will power a typical tiny house. This assumes an average sized solar panel of around 300 watts, which would generate around 4,500 watts of power from the sun.

thetinylife.com - Solar Panels For Tiny Houses: How I Went Off Grid With My Tiny House
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It’s hard to imagine that I’ve been powering my tiny house off solar panels for my tiny house for over 7 years now! Not having a power bill for almost a decade has been incredible. With that in mind, I wanted to get some real-world experience with my system to give you all the full picture of what it’s really like to power your tiny house with solar: how many panels, how much does it cost, and more.

Solar Panels For A Tiny House

Many people have asked me about putting solar panels on a tiny house because I’m one of the few out there that is totally off the grid in my tiny house. I’ve had to figure things out like how to run my air conditioning off solar, how to cook with solar in a solar oven, and how I use solar generators as backup power in a pinch. Tiny houses are a great candidate for solar power because the smaller space makes for low power needs. While the traditional home in America uses around 30 KWs per day, my tiny house uses around 3 KWs per day. Every decision I made during my tiny house build, from choosing LEDs lights, to a super-efficient minisplit system, and an on demand hot water heater all were chosen to reduce my power consumption. Since I built my own house, these decisions were pretty simple and, in the end, didn’t cost me much more. Any additional costs for things like a high SEER rating HVAC system quickly paid for themselves by letting me have a smaller solar panel array and batteries.

How Much Power Does A Tiny House Use?

A tiny house will use around 4 KWs per day. Typically, around 80% of that power will be used for heating and cooling, assuming you cook and heat water with propane or natural gas.

Here is an example of my power usage breakdown:

Minisplit (heating/cooling): 3,000 watts per day

Fridge: 780 watts per day

Lights: 100 watts per day

Cell Phone: 30 watts per day

Laptop: 240 watts per day

Total: 4,150 watts per day

How Many Panels Do You Need To Power A Tiny House?

15 solar panels will power a typical tiny house. This assumes an average sized solar panel of around 300 watts, which would generate around 4,500 watts of power from the sun. This would cover all your power needs including some heating and cooling, but require you to have a gas cook range and a propane heated hot water heater. If you live in a particularly cold climate, you’ll most likely need to supplement your heating with a propane heater too.

How many solar panels can you fit on a tiny house roof?

Generally speaking, you can only fit around 2 solar panels on a tiny house roof. This presents a real challenge because today you can really only expect to make around 20 watts per square foot of solar panel in ideal circumstances. That means you’re only going to be able to fit around 600 watts of solar production on a tiny house roof, which isn’t a whole lot.

Mounting Solar Panels On A Tiny House Roof

Many people want solar panels on the roof of their tiny house, but I opted for a ground mounted solar array, which I highly recommend. Tiny house roofs only have around 200 square feet of space and since most roofs are pitched, you can really only mount panels on one side. This means you only have around 100 square feet of space for panels. What I did was mount my solar panels on stands on the ground. After considering all the options: roof mounted, pole mounted, solar trackers, and fixed ground mount, I’m really happy with my decision. The benefits of a ground mounted array are huge: being able to easily clean my panels, clear off snow that covers my panels after a snow fall, keeping the panels cooler (increases their efficiency) and being able to shade my house while placing the panels in an open field. The biggest benefit of ground mounting my panels is that I could have a way bigger solar panel array. This meant instead of 600 watts on the roof of my tiny house, I could put 4,000 watts on the ground in the field right next to my tiny house.

My Tiny House Solar Panel System:

To get your tiny house setup on solar you’ll need the following parts: your panels, batteries, a charge controller and an inverter. Simply put, your solar panels take the energy from the sun an converts it to DC power, that then flows to the charge controller which regulates the flow of power to the batteries or the inverter, the batteries stores power for later and the inverter converts the DC power to AC power, which your house uses.

Here’s the key details of my solar power system:

3,975 (3.9 KW) of panels Schneider SW 4024 – fifteen, 265 watt panels

1,110 amp/hr battery storage

24 volt system

My Tiny House Solar Setup:

(15) Canadian Solar CS-6p 265 Watt Poly Black Frame

Schneider SW 4024 Inverter

Schneider MPPT 60 Charge Controller

(12) Trojan L-16 6v 370 AH Flooded Lead Acid Batteries

Schneider System Control Panel

Schneider Interconnect Panel

Midnight Solar MNPV 80AMP Dinrail Breaker

Midnight Solar Surge Protection Device AC/DC

50 Amp RV power Inlet

How To Build A Solar Power System For Your Tiny House

Before anything I needed to determine the best placement for the solar panels to make sure it had good solar exposure and didn’t fall into shadows too much. To do this I used a tool called a “solar path finder” which is a semi reflective dome that you position at the location, then snap a photo. The photo is then loaded into a program and spits out a whole bunch of calculations.

Calculating Power Production

Once you upload the image into the software and then trace the tree line outline, you enter in your location, date and time. It then can calculate how much power you’ll produce based on 30 years of weather patterns for your exact location and tree coverage. Then it spits out all the calculations: With that in mind, I knew what I could expect out of the system I had designed. It also was a way to verify my assumptions. Once I verified that the system was going to be well suited to my needs, I had to build my panel support racking. I did this out of pressure treated 4×4’s that were each 10′ long. These things about 300 lbs each so I don’t have to worry about the wind picking up the panels. I opted to build them because it was cheaper than some of the turn-key option out there and most of the for purchase ones required me to cement in the ground; I rent my land, so I wanted a mobile solution. If I remember correctly it was about $500 in materials to build this part.

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Many people have asked why I didn’t mount these on my tiny house roof. You technically can mount on your roof, but honestly, the number of panels that you need to practically power your house is too many for the roof.

There are some other major bonuses of being on the ground:

Much cooler, roofs are very hot places in the summer and solar panels drop in efficiency when hot I can put my house under deciduous trees, this means in summer I’m in the shade, in winter I get the solar gain

Way easier to clean and monitor

Cleaning your panels is pretty important because you loose efficiency as residue (bird poop) builds up. Also, as I learned just a few days ago, when it snows, you need to clear your panels. Cleaning becomes super simple and a lot safer when you don’t have to climb onto a roof via a ladder. Just this week we got a decent snow, 3 inches, which is quite a lot for Charlotte. The first thing I had to do when I woke up was clear off the panels because, with the snow, they made no power. This was compounded because since it was cold, I needed more heat. I can’t imagine having to drag the ladder out and try climbing on an icy roof… No Thanks.

Choosing To Wire For AC Or DC From Solar

Many people have read around the internet that DC (direct current) is a more efficient power way to power things. Generally speaking, everything in a traditional house is wired for AC (alternating current), but if you’re putting solar in a tiny house and building your own house, the question becomes relevant when you’re starting from scratch. Solar panels produce DC power, so you have to decide how you’re going to handle it. Most of the advice to wire a house for DC power comes from older sources who haven’t updated; these could be old articles written on the topic (consider anything more than a year out of date with how fast solar is improving) or from someone who hasn’t caught up with the latest equipment. Back in the days, the drive to wire a house in DC power comes from two main things: there was power loss through inefficient inverters (converts from DC to AC) and from the fact that on paper DC is, in fact, more efficient. Where this falls down in modern times is that inverters have come a long way and while there is some loss in power through the converting of AC to DC, it’s quite minimal. The other factor here is that any inefficiencies (of both the conversion to AC and the less efficient nature of AC) can be easily offset by the addition of 1-2 panels to your array. This begins to make even more practical sense today because if you wire for DC, you’ll be limited to DC powered appliances, which typically cost two to three times the cost of their AC equivalents. That all means that you can actually have more power with AC, even after the losses through inefficiency, for less money. This is because the savings from going to AC appliances over DC will leave you with more cash, even after you buy 1-2 more panels. To put it simply, convert to AC, add a few more panels to your array and stop worrying about AC vs DC.

Installing Solar Panels For My Tiny House

After calculating the ideal location and building my stands, I installed the solar panels. This part was pretty quick and the stands worked out perfectly. The panels are 250 watt Canadian solar panels. They are wired in groups of three, then paralleled into the system. To give you a sense of scale, these panels are 3.3 wide and about 4 feet tall.

Building My Battery And Inverter Cabinet

Next, I built a cabinet to house all the gear. I wanted a stand alone space because the batteries are so heavy. At 118 pounds each, plus cabling and other equipment, the whole unit is over 1,100 lbs. The top and bottom sections are divided so that the gasses from the batteries don’t go up into the electrical section for a very important reason. Looking at the cabinet, on the sides of it, you can see the vents. When you use lead acid (LA) batteries you have some off gassing as the batteries discharge and recharge. These gasses are volatile and can ignite, possibly leading to an explosion. To take care of this I installed two vents like this which provide adequate venting.

Choosing Batteries For A Tiny House Solar Panel System

I choose lead acid batteries over AGM (absorbent glass mat) because LA’s have more cycles and cost a bit less. Lithium Ion at this point is cost prohibitive, around $10,000 for the equivalent capacity. I choose these 6 volt batteries because it was more economical over other options and trojan is a pretty reputable name in the industry. My batteries should get about 4000-5000 cycles (11-14 years) before I need to replace them. I figure in about 5 years battery technology will have progressed so much I’ll change early. New batteries will cost me about $5,000 of the lead acid variety.

Wiring My Batteries For 24 Volts

The batteries are wired in series parallel. The batteries are 6 volt each, in series of 4 the create a 24 volt unit. Then I have two of these 24-volt units in parallel. The reason I choose to go 24 volts over a 48 volt (which is more efficient) was that the equipment was a little cheaper and it allowed me to future proof my setup.

Future Proofing My Solar Panel System

Going with a 24 volt system also allowed me to select components that I could add more panels and batteries very easily without doing equipment upgrades (just a factor of the abilities of the units I choose). This way I can add up to 15 panels and a lot more batteries without upgrading the electronics. A big draw for me to the system I choose was that I can also stack these inverters, so if I ever go to a normal sized house, I just add another unit and it just plugs into my current one.

Wiring A Tiny House For Solar

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In this photo going left to right: Din Breaker Panel, Charge Controller, Interconnect w/ control panel, inverter.

In general, the power flows in the same manner (but not exactly).

Breaker Panel: manages power from solar panels

Charge Controller: manages power to batteries etc.

Interconnect: a main junction box and breaker, holds control panel interface

Inverter: takes power in many forms then outputs to the type of power you need

How To Connect Solar To A Tiny House

Once the power goes through the system it outputs from the inverter as AC power. This AC Power flows out through a huge cable that you can see sticking out of the bottom of the inverter then goes right. From there it runs to this: This is a 50 amp RV style plug. The reason I did this was twofold. City inspectors are less picky when it comes to non-hard-wired things. This setup also lets me roll into any RV campground and hook up seamlessly. The plug goes into a 50 amp RV female receptacle. This is important that you don’t have two male ends to your cord. This is dubbed by electricians as a “suicide cord” because if you plug into a power source, you have exposed conductors that are live; accidentally touch them, you complete the circuit and zap! You want a female end to your cord so that you reduce the chance of being shocked. I also turn off my main breaker at the power source when I make this connection, then turn it back on. If all these mentions of watts, volts, amps, amp hours etc are making your head spin a little, you may need to go back to the basics. I have an ebook called Shockingly Simple Electrical For Tiny Houses which guides you through all the basics. As of now, it doesn’t go too deep into the solar aspects, but the basics of electrical, wiring, power systems and determining your power needs are covered in depth and designed for those who are totally new to the topic. So once the power passes through the power inlet it goes to the panel. Near the bottom you can see the backside of the power inlet, it has a large black cord coming out of it, into the box and ties to the lugs. From there it goes out to the house.

Grounding Your Solar Array

Here is my grounding wire for my system. This is actually one of two, another is located at the panels themselves. My house is also grounded to this through the cable hook up and to the trailer itself. A really important note: ground depends on a lot of things, one of which is if you house electrical panels is bonded or not, if you don’t know what that means, read up on it, it’s very important.

Using A Backup Generator

The other component of this system is the generator which I used for the first two years and then opted to upgrade my system because they were such a pain to use. In the winter months, I sometimes needed to top off my batteries every now and then, basically when it’s been really cold and very cloudy for a week or more. I had a Honda EB2000i already which I really like. It’s very quiet and small. The one downside to the Honda is that it only does 1600 watts and only 120V and I needed more power and 240V. To charge my batteries, I had to have 240 Volts, which lead me to get another generator, a 5500 watt 240 volt Generac for $650. This generator proved to be a major headache and lead me to upgrade my system just to not have to use it anymore. Here is a video that compares the two generators in terms of size, noise, output, and price.



Tiny House Solar Panel System Costs

The big question when it comes to doing solar or not is of course cost. Everyone would like to have solar, but costs are a real barrier. My decision was made pretty easily when the power company informed me that I would have to pay $15,000 just to run their power line to my house, only to have a power bill each month. My initial version of my solar panel array and batteries cost me around $14,000 with the added benefit of no power bills ever again and a $7,500 tax credit back, the decisions was a simple one. I later upgraded to a larger system for another $5,000, of which I got another $2,500 tax credit. So, for me, I was able to actually save money from day one. That said, I had to bank roll that huge cash payment which most people cannot do. Here is a rough break down of costs for my upgraded solar panel system:

Inverter: $4,500

Charge Controllers: $1,200

Control Panel: $300

Batteries: $4,000

Solar Panels: $4,000

Breakers + Boxes: $800

Battery Cabling: $300

PV Wire + House Tether + Romex: $500

Electrician (labor): $2,000

Is Solar Practical For Tiny Houses?

In general, I think for tiny houses in one spot, solar is very realistic. Even if you don’t start out on solar, the cost savings of living in a tiny house can let you save up for the install pretty quickly. When I rented an apartment, I was paying $1500 a month, compared to my tiny house that costs me about $15 a month (not a typo). Living in a tiny house allowed me to save a ton of money while having a comfortable home. So that’s the surface level details of the system, I’m going to be doing something in the future which will be a how to size, choose parts, hook up and all the other details of doing solar for your tiny house.

Your Turn!

Do you want to do solar for your tiny house?

thetinylife.com - Solar Panels For Tiny Houses: How I Went Off Grid With My Tiny House
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