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There is nothing quite like enjoying a cool drink on your boat while enjoying the view. But have you ever wondered how many solar panels it would take to run a boat fridge? Is it even possible? Well it is, but there are a few things you need to consider before trying it out.
A standard boat fridge that uses 25 amps a day requires at least a 100W solar panel to operate. A 50ah battery is also needed to keep the fridge and freezer running once the sun goes down and the solar panel no longer produces power.
What Solar Panel Size is Needed For a Boat Fridge?
The solar panel sizes and number you will need depends on what type of boat refrigeration you have. Depending on the fridge, you may not require solar power at all or you may have to use several panels, batteries and an inverter.
Boat fridge power is measured in amps. Multiply amps by the voltage to get its watts, and you will know how much solar power is required.
A 12V boat refrigerator that draws 5 amps an hour and is on for 10 hours a day requires a 100 watt solar panel and a 100ah battery.
5 amps an hour is 60 watts:
5 x 12 = 60
Instead of 60 watts, get a 100 watt solar panel so you have extra power in case the weather turns cloudy. Make sure also your solar panel has an efficiency rating of at least 20%.
Thanks to its compressor, a fridge does not actually run 24/7, but cycles on and off. Assume it is on for 10 hours a day, it would require 50 amps or 600 watts.
So if we use the example here, you will need something like the Renogy 12V Monocrystalline Solar Panel to power the fridge. If you need to run the fridge for more than ten hours you can always connect more panels to the system.
A 100 watt solar panel can produce up to 500 watts a day with 5 hours of sunlight, not enough for the fridge. Even if you add another solar panel, you still won’t be able to run the fridge when the sun goes down. This is where you need a battery to store the solar energy.
As for recommendations, we like the VMAX MR127 12V AGM because it runs on RVs, boats and various other configurations. Combine this with the Renogy and your boat fridge is set.
Battery + Solar Panel
This is where the battery steps in. With a 100ah deep cycle battery it can power your fridge throughout the night or if there is a downpour.
Notice we say a 100ah battery, not 50ah. Lead acid batteries should be recharged when capacity drops to 50%, so you need a 100ah battery if the fridge requires 50ah. High end lithium batteries can be fully discharged.
You can use the same steps for any fridge regardless of size. But you should add 10% to 20% to the solar power as usage can be affected if the weather is not favorable.
Boat Fridge Solar Power Chart Guide
The following chart shows the solar power requirements for common types of boat refrigeration. The solar panel and battery specs listed below are the minimum.
|Amps Per Day
|Solar Panel Size
|Frigoboat Keel Cooler 6 cu. ft.
|12V Portable Compressor Cooler 40L/42QRT
- To keep it simple, the average boat fridge draws 5 amps an hour. You can assume that it runs for about 8 hours a day based on a regular on/off duty cycle.
- These are only general guidelines for these models. Top brands manufacture different types of boat freezers and coolers with varying specs.
- Check the specs before you buy, the wattage, amps drawn, voltage etc. Some boat coolers can run on 12V/24V, 120V etc., while others can only use one power source.
- The batteries and solar panels are only for the fridge. If you are going to run the boat motor on solar you will need a larger system.
- Keep in mind that manufacturer specs are for general conditions. The weather in your area, your boat specs, etc. can affect fridge power consumption.
Which Boat Fridge is Best For Solar?
The answer depends on how much time you spend in your boat, the climate and what type of boat you have.
An ice chest does not need solar power, or any power source. Just fill it up with ice and put your food and drinks in it. If you boat infrequently, a simple ice cooler will do. A 2 cu. ft. chest holds about 60 quarts.
Ice chests are affordable and do not have any electrical components. These are great for small boats, fishing vessels or extra storage for yachts. The best ice chest can keep food fresh for up to five days.
Portable Compressor Freezer
These freezers require up to 40 amps to run. The capacity ranges from 20 to 115 quarts. A 300 watt solar panel system and 200ah battery is recommended.
Portable freezers can run on AC or DC power so it is ideal for boats and campers. The larger compressor freezers weigh close to 50 lbs. and will take up considerable space.
If you spend a lot of time boating, a portable solar freezer is worth looking into. Just make sure you check the specs so you will know how many solar panels and batteries will be needed.
Other Boat Fridge Types
Other options include front loading refrigerators, icemakers and DIY icebox conversions. In some cases solar panels are an option, but it depends on the design.
Front loading freezers for instance, are usually built into the boat and runs on its own AC or DC system. Due to the need for consistent power, these freezers run on a battery bank and usually has an integrated inverter.
Icemakers are often staples on large boats and used to produce large amounts of ice. A typical icemaker draws 2.5 amps from a 12V system so a 100 or even 50 watt solar panel is enough.
An icebox conversion involves turning the icebox on your boat into a freezer or refrigerator. You have to buy the compressor and evaporation components, and is only for advanced DIYers. The number of solar panels required depends on the specs you will build.
How Many Batteries to Run a Boat Fridge?
Solar panels can only run your boat fridge during the day. You need a battery bank to run it for an entire day. Of course you won’t just be running the fridge but other appliances on your boat so you have to calculate your total power usage.
As a general guideline, battery requirements are:
- 25-35 ft. boats: boat used overnight only, 200ah
- 30-50 ft. boats: for cruising up to a week or longer, at least 300ah
- Yacht and large boats: spends several weeks on cruise, lots of food and hot climate, 400ah minimum
These are overly simplified because fridge use will vary from one boat user to another. But in general if
you spend more than a few days on your boat, get a 200ah battery and a 300 watt solar array.
When calculating solar panel and battery requirements, always factor in your own situation. While a 200ah battery may be enough for a 35 ft. boat, it might not apply in your case. If you are holding a party and there are several people onboard, more battery power will be needed.
Boat Fridge Battery Power Usage Calculation
The calculations are easy to understand as long as you remember the conversion formula (amps x volts = watts).
Suppose you have a 12V portable fridge. It draws 4 amps an hour and runs for 8 hours a day. That is 32 amps or 384 watts. You need a 50ah lithium battery that can be discharged fully or a 100ah deep cycle lead acid battery with 50% DOD. If you want to run the fridge on solar panel you need 50 to 100 watts to produce 4 amps an hour.
Remember that solar panels and batteries work together. You can run the fridge on solar power in the morning and let the battery take over in the afternoon.
Or you can just let the battery run the fridge. As long as the solar panels are connected it will keep the battery charged. When night time comes your battery will still have full power. Of course if you have another power source it will not be an issue.
Factors That Affect Boat Fridge Solar Power Consumption
- Voltage. Some boat refrigerators use only 120V AC, others 115V, 12V, 24V, DC, or is compatible with all of them. The amps required by the battery will vary depending on the voltage. The higher the voltage, the lower the amps drawn. Your solar panel voltage must also match the battery.
- Water temperature. The hotter the temperature, the more power it will take for the freezer / fridge to keep its contents cold. Keep this in mind if you are cruising in a tropical location.
- Capacity. The larger the freezer, the higher the potential power use. But it also depends on how filled the freezer is.
- Compressor. compressor specs vary widely depending on the freezer / fridge / cooler. Some are energy efficient, while older models may add as much as 25% to the power consumed.
As you can see there are a lot of options when it comes to boat refrigeration. Whether you opt for a simple ice chest or a full sized refrigerator freezer, there is a solar power system that you can use.
I am an advocate of solar power. Through portablesolarexpert.com I want to share with all of you what I have learned and cotinue to learn about renewable energy.