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Cabins come in different sizes, from a single individual design to those large enough for entire families and entertaining friends. Let us go into the numbers and figure out how many solar panels your cabin will need.
Cabin solar panel requirements depend on how many appliances are running and how much time you spend there. If you go there 2-3 days a week and use a small TV, LED lights and a mini fridge, a 200W solar panel, 1000W inverter and 200ah battery will be enough.
How to Calculate Your Cabin Solar Power Needs
The two biggest factors are the appliances you’ll be using and how often you stay in the cabin. Cabin sizes range from 12 x 12, 16 x 30 or 24 x 48 etc. but it doesn’t matter as much as the power consumption.
To start, remember these two equations:
Watts / volts = amps or current
Amps x volts = watts
Add the watts for all the appliances you will use every day plus 20% for reserve power. This is how much energy your solar array must produce a day.
How much time you spend in the cabin is another factor. Power consumption will be lower if you only go there during weekends compared to spending 6 days a week there.
Even so there might be some things you need to keep running even if you are not there. You might want the heater to remain operational to prevent pipes from being iced for example.
List all the things you need to keep running while you are away (heater, fridge etc.). Add up the total watts and you should know how much solar power is required to keep them going.
You have a small cabin and go there 2 days a week. The only appliances you use are a three LED lights, a 20 inch TV, a fan and a fridge.
Majority of these appliances do not run 24 hours a day, so you have to estimate how many hours you’ll be using it.
Example: a 20 inch TV is about 20 watts a day. If you watch TV for 4 hours a day that is 80 watts.
A LED light consumes 8 watts an hour. If you use it for 8 hours a day that is 64 watts.
Repeat this with all the appliances you want to use. Examples:
- 3 LED lights: 192W (8 hours a day)
- 20 inch TV: 80W (4 hours a day)
- Fridge 480W (8 hours a day)
The total is 752 watts. Add 20% for reserve power and you get 940 watts.
You need a solar array that can produce 940 to 1000 watts a day to run these appliances. The ECO WORTHY 1000W 24 Solar Panel Kit should be enough to meet this requirement.
What if the appliance is used for less than an hour? if you have a 700W microwave and use it for 20 minutes a day:
700 x 0.2 = 140
A 700 watt microwave used for 20 minutes consumes 140 watts. Just repeat this with any appliance or solar power tool that plan to use. This takes more time, but it gives you a more accurate picture of how much solar power your cabin really uses.
The appliances you have, the more solar power you are going to need. You should also provide some leeway in case your usage goes up.
How Many Solar Panels Do I Need For a Cabin?
It depends on the solar panel size and how many hours of sunlight are available.
A 200W solar panel can produce 1000 watts a day with 5 sun hours. But this assumes the panel can sustain a 200 watt an hour output. In reality the panel might generate 175 watts or less depending on the panel orientation, shading etc.
A better option would be a 250W or 300W solar panel. With at least 5 hours of sun it will produce more than enough energy to power those appliances.
Another benefit of larger solar panels is they cost less per wattage. Second you don’t have to install as many panels on the roof. Third, a large solar array can generate more power than you need, and reserve power is always good.
These sample calculations assume a very basic cabin for one person. Family sized cabins need more power because power consumption is higher.
However you can still use the same process. Estimate how many hours you will use each appliance, add everything up plus 20% and you have the ideal solar array size.
Factors That Affect Solar Panel Production
- Location. If your cabin is surrounded by trees, the solar panels will receive less sunlight. So go over the location first and determine how much sun actually gets in.
- Panel orientation. Solar panels should face south to receive the highest amount of sunlight possible.
- Efficiency. Solar panels have efficiency ratings that determine how much sunlight gets converted. A rating of 21% and up is ideal.
- Season. Solar panel performance is at their peak during summer and is at its lowest during winter. Plan for this before you set up a PV array.
- Geography. Some parts of the US get more sun than others. A cabin with a 5kw solar array is going to generate more power in the West than a 5kw solar array in the Northeast.
How Many Batteries Do I Need For a Cabin?
The rule of thumb is the battery storage should be 3 times your daily solar power consumption, at least for average sized houses. For cabins, this will depend on how much time you are are there and how much power you need.
The typical American home uses 30kw a day. You have a simple cabin with only basic appliances and consume half, 15kw daily or 15000 watts.
If you want to have three days’ worth of reserve power, you would need a 3750ah battery bank, or 12 x 300ah 12V batteries. You can reduce it to six if you use 24V batteries though they cost more.
But you probably won’t even need that much because cabins are often used for recreation or vacation. If you only go there during the weekends you probably won’t even need batteries, the solar panels are enough.
But batteries are not just for storage. They also serve as another power source when solar panels cease to produce power.
Solar panels can only produce power during the day, 5 to 7 hours maximum. With a battery bank you can run your appliances throughout the night. With enough stored power your cabin will still have power even if it rains.
Battery Cabin Sample Calculation
If you’re going to stay in the cabin for several days, you must have enough battery reserve power in case of emergency. Here are some suggestions.
Earlier we mentioned how important it is to have reserve power. If you consume 8kw a day and your solar array generates 10kw, you need a battery bank to store the extra 2kw.
10kw = 10000 watts
10000 watts / 12 volts = 833ah
833 / 300 = 2.7
You need 3 x 300ah 12V batteries. Three Lossigy 300ah 12V batteries should cover your needs.
If you want to have enough power for a day in case of rain, use the same formula. And if you consume 5 kw / 5000 watts a day, divide by the battery voltage to find its amp equivalent. Now divide that figure by your preferred battery size.
5000 watts / 12 = 416
416 / 200 = 2
It takes 2 x 200 12V batteries to store 5000 watts of power.
If you end up using all that reserve battery power, consider doubling the capacity. Lead acid batteries should not be fully discharged, so by doubling the capacity you can maximize its potential and life cycle.
What Inverter Size Do I Need For a Cabin?
Solar panels generate DC power but most household appliances run on AC, so you need an inverter to convert DC to AC.
Total watts used per hour plus 25% = inverter size
If you need to run 2000 watts at the same time, you need a 2500 watt inverter. The extra 25% is for any power surge and also to make up for the inverter inefficiency. Better yet, get a 3000 watt inverter for more power. Our personal choice is the PowerDrive PD3000 due to its power and reliability.
The inverter draws from the battery bank so the system is only as good as its capacity. If you need 2000 watts an hour, the battery bank must supply that amount. In this case, 2000 watts is equal to 166.6 amps or a 200ah battery, the closest available size.
The bigger the battery size the better, because you want the battery to supply extra power to the inverter. If your cabin is off the grid, the solar panels will charge the batteries.
If we assume a 300W solar panel produces 270W in less than ideal weather, that is 1350 watts in 5 hours. A couple of 300W solar panels should be able to charge a 200ah battery bank to keep the inverter going.
Once you determine how many solar panels you will need, it is just a matter of getting the right components. The easiest way to do this is to buy a solar power kit which includes all the parts required to set up a solar powered cabin.