Wednesday, July 17, 2024

How Many Solar Panels Do I Need For My Cabin

Wiring Your Solar Panels

Update on 470 watt solar system for my off grid cabin

When we talk about recharging batteries, two parts of the electric current are important: amps, and voltage.

If our battery bank runs at 12 volts, we want to recharge it with a current at or a little above that 12 volt rating.

Once weve reached our desired voltage in our charging current, additional amps result in a faster charge time.

EX: Our battery bank has a 400 amp/hour capacity and runs at 12 volts

A 12 volt 40 amp current will recharge our battery in around 10 hours.

A 12 volt 10 amp current will recharge our battery in around 40 hours.

You may look at this and think that maximizing your amperage is the way to go.

However, that has its own problems.

High amperage currents charge our batteries faster, but they also require much thicker wiring and specialized connectors.

As electricians will tell you, high amps means high heat.

Wed have to make sure our cables were low gauge to handle the increased heat.

High amperage current also doesnt play-nice.

Expensive and bulky connections are necessary to deal with high amperage current.

Additionally, if our solar panels are far away from our battery bank, we can also run into problems of voltage loss, which occurs in low voltage current over long distances.

A 14 volt 40 amp current could drop to below usable levels if the current needs to travel over long distances.

So how do we reconcile these two facts?

If we try to charge our batteries with a high voltage current it will damage them.

Advantages Of Solar Panels

Lets start with the advantages of solar panels in order to give you an idea of why you should choose them for your garden building in the first place. First of all, they are a smart investment even though installing them might not be the cheapest option, it will pay off over time, as they last 20 to 30 years and can substantially reduce your electricity bills or even free you from paying any electricity bills whatsoever. They will also allow you to protect yourself from the rising electricity prices as well as any possible power outages. In addition to that, they require nearly no maintenance, apart from occasional cleaning.

Of course, the environmental advantages of solar panels are perhaps even more important than the technical ones, as they are a simple and great way of switching to renewable energy. Even if you still use electricity from the main power grid together with solar panels, it can still considerably reduce your carbon footprint and, if you install a battery, you can completely switch to solar power, making your garden building self-sustainable.

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 dont know what that means, read up on it, its very important.

Read Also: How Does A Solar Ppa Work

What Is The Difference Between Gel Agm Fla And Lithium Batteries

Battery technology varies widely and advancements are being made all the time.

Currently, the most commonly installed batteries are Gel, AGM or Lithium. FLA use dated technology and we recommend steering clear of them.

Lithium batteries are significantly more efficient than Gel or AGMs so can be discharged to a much lower level.

This explains why you need a smaller Lithium battery than either AGMs or Gels.

But this doesnt mean a lithium battery is always the best option.

To assess which battery is most cost effective and best suits your needs, use our battery comparison calculator.

More information, read our detailed post on campervan batteries.

Can You Connect A 100w Solar Panel To A Solar Generator


A solar panel can be connected to a solar generator and used to recharge the unit. However, PV modules are not always required for solar generators though they are compatible.

A portable solar generator or solar power station is basically a battery. You charge it via an AC wall outlet, DC or solar panel and it runs whatever device you connect to it. Generators have multiple inputs and outputs and capacity ranges from a few hundred watts to some large enough to power a house .

Because solar generators can be charged by AC power, a solar panel is not required. Many power stations dont have solar panels built in but you can hook up one easily. Most people charge their generator with AC and use the system while camping. If the power runs low thats when you can use a solar panel to recharge the unit.

There are many types of solar generators, some with more features than others. Check first if it is compatible with your 100W solar panel or if there is already one built in. You may also need more than 100W to recharge the generator, depending on its capacity.

Also Check: How Much Can Solar Panels Save Me

Read Also: How Many Amps Does A 300 Watt Solar Panel Produce

Solar Panels For Commercial Businesses

For businesses, solar panels might represent an environmental good or a financial strategy.

Whatever the reason could be, solar panels are a great move for all sizes of businesses.

Just as in residential cases, the size dimension of your system will be determined by the same factors listed in the how much power do I need section. And the size of solar panels for commercial businesses are just the same as the ones we mentioned above.

Nonetheless, since businesses require on average more power than homes, the typically used solar panel size in businesses is 72-cells size or more, like that of 96-cells.

The difference lies in the size of the solar panel array, given that the power demand for commercial businesses is higher than for residential use.

The figure below illustrates an approximation of that comparison.

An average home fits its energy needs with systems of around 6 kW or 7 kW. Businesses will require larger systems. In this case, expect to occupy a larger rooftop surface to cover your companys energy needs.

If you install a 6 kW system with, say, 20 average-sized solar panels, expect to occupy a surface of 27 ft. wide by 13 ft. long on your rooftop.

The table below shows a rough idea of the common size of solar panels for commercial businesses and the expected price range

Common system sizes for commercial businesses and expected price range.

System size

Also Check: How Many Watts Solar Panels To Run A House

The Little Hobbit Has Stepped Up To The Challenge

“We just wanted to say how impressed and how much of a life saver our little Hobbit has been! It was fitted a few months ago in our holiday home in Rhu, Scotland, which is a large open plan conversion in a Victorian house. This weekend our boiler decided it was not going to play ball. The little Hobbit has stepped up to the challenge, providing heat to a very large area, about twenty eight foot by twenty four foot with a high ceiling of about eighteen foot, keeping the room reasonably warm, warm enough for us not to use cardigans!

Alan W

Recommended Reading: What Size Cable For Solar Panels

What Peak Sun Hours Should I Select

The amount of sun falling on your solar panels affects how much energy they can harvest.

Because the suns position in the sky varies throughout the year, the amount of energy they can harvest also varies.

The map above gives an estimate of peaks sun hours in winter and summer throughout the world.

Use the lowest number of all the locations you will travel to.

For example, if you plan to travel:

  • in North and South America following the summer, use 5 hours
  • in Europe and Africa in winter, use 3 hours.

If you want to use more precise figures, this website gives average peak hours in a far more scientific way than our picture.

How To Build A Solar Power System For Your Tiny House

BIG solar upgrade for the cabin!

Before anything I needed to determine the best placement for the solar panels to make sure it had good solar exposure and didnt 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.

Recommended Reading: Can An Air Conditioner Run Off Solar Power

Choosing Batteries For A Tiny House Solar Panel System

I choose lead acid batteries over AGM because LAs 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 before I need to replace them. I figure in about 5 years battery technology will have progressed so much Ill change early. New batteries will cost me about $5,000 of the lead acid variety.

How Much Solar Power Will You Need

To find out your average energy usage, check your past utility bills. More precisely the last 12 months of your bills . Look for the total number of killowatt-hours you consumed every month.

Sum the numbers up and divide them by 12 to get the average. An easier way to determine your total energy consumption for the past year is to simply call your utility company and ask them to provide you the details.

Based on the data available from the U.S Energy Information Administration, in 2013 the average family home in the United States consumed about 900 Kwh of electricity per month. Thats 30kWh per day.

Obviously your household can consume more or less electricity depending on how big your house is, how many family members live in it, the appliances you have and how energy efficient you are.

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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 youre only going to be able to fit around 600 watts of solar production on a tiny house roof, which isnt a whole lot.

How Many Batteries Are Needed To Supply 1000 Watts

How Many Solar Panels Do I Need For My Home?

Another way to put this question is, how many batteries do I need to provide my solar system with 1000 watts? Solar panels rely on solar power of course, but if the sky is cloudy and you want to run it, how many batteries would it take?

A 200ah lead acid battery can supply 1000 watts for one hour, and large batteries can provide even more power for longer periods. If the battery is 12V that is 2400 watts, but with a 50% depth discharge only 1200 watts can be tapped. A 24V battery can also be used if your solar panel has the right voltage.

A 12V 100ah lithium battery, including the Weize LiFePO4 can supply1200 watts if fully discharged . Here are the watt equivalent for various 12V batteries.

  • 100ah 1200
  • 400ah 4800
  • 500ah 6000

Any of these batteries can supply 1000 watts to a solar system. The difference is the duration. A 300ah battery with a 50% DOD has 1800 usable watts, good for an hour and half, maybe an hour and 45 minutes.

If you have two 250ah batteries, that is 500ah or 6000 watts. Even if only 3000 watts are available, the battery can carry a 1000 watt load for 3 hours. Use the guide above and you can see how many watts they can provide.

With a lithium battery it is a different story. You can fully discharge the battery, or close to a full discharge. No need to cut the usable watts in half. Though the cost is at a premium, lithium batteries are worth considering for heavy loads.

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How Do I Use This Solar Battery Bank Calculator

  • Enter every electrical device and component youll power form your camper batteries
  • Enter the watts each device uses
  • Enter the maximum number of hours each day youll use the device
  • Select whether each device is DC or AC
  • Enter the amount of contingency you want to add to the total usage
  • Select the battery type you will install
  • Select the minimum expected peak sun hours
  • Select the type of solar charge controller
  • The RV solar calculator provides the minimum size solar components needed based on the information entered.

    How To Heat Water With Solar Hot Water Heaters

    In addition to producing free electricity, solar is also great for heating water. Cost-effective solutions can range coiling up a black water hose inside a black box with a window so that the suns solar UV rays can be absorbed and used to heat hot water and store it in an insulated tank all the way up to very fancy systems that use copper tubing and a host of add-on features that will keep the water from freezing at night when the sun isnt shining.

    In addition to household hot water, solar water heaters can be used to heat stock tanks and ponds, water troughs, greenhouses as well as water used for outdoor bathrooms, hot tubs, showers and radiant floor heating.

    Read Also: How Does A Residential Solar System Work

    Determine Your Daily Energy Usage

    You’ll want to look to your electric bill for this information. It will usually be printed as your monthly kilowatt-hour output. To calculate your daily kilowatt-hour output, you will need to divide that number by 30, then multiply by 1000 to convert the number into watt-hours. Which translates to one watt of power sustained for one hour. This is the first step in determining your solar battery bank size.

    Choosing To Wire For Ac Or Dc From Solar

    Cabin Life – My 100 watt solar setup

    Many people have read around the internet that DC is a more efficient power way to power things. Generally speaking, everything in a traditional house is wired for AC , but if youre putting solar in a tiny house and building your own house, the question becomes relevant when youre starting from scratch. Solar panels produce DC power, so you have to decide how youre going to handle it.

    Most of the advice to wire a house for DC power comes from older sources who havent updated these could be old articles written on the topic or from someone who hasnt 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 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, its quite minimal. The other factor here is that any inefficiencies can be easily offset by the addition of 1-2 panels to your array.

    To put it simply, convert to AC, add a few more panels to your array and stop worrying about AC vs DC.

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    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, youll most likely need to supplement your heating with a propane heater too.

    Is Solar Practical For Tiny Houses

    In general, I think for tiny houses in one spot, solar is very realistic. Even if you dont 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 . Living in a tiny house allowed me to save a ton of money while having a comfortable home.

    So thats the surface level details of the system, Im 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?

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    Calculate Your Solar Panel Needs

    Solar panels are usually rated to put out 150 to 370 Watts. And that output can vary a lot by size and type of panel. Plus, thats the output you can expect with direct sunlight. So to figure out how much each panel can generate per day, youll have to take a few factors into account.

  • Where your cabin is. Some areas of the world get more direct sunlight than others. The Renewable Resource Data Center has some really good maps and information to help you figure out about how many hours of peak sunlight you can expect in your location.
  • How shaded your cabin is. If youre in a wooded area, you likely get less hours of peak sunlight than they state.
  • The angle of your roof . If you dont have a nice pitch on the south side of your cabin, then you wont get as many hours of direct sunlight.
  • If you determine that youll get about 4 hours of direct sunlight and youre using 250 Watt panels, then a single panel will generate around 4 x 250 = 1,000 Watt hours or 1 kWh per day. So if you need 10 kWh per day, then you need 10 panels.

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