The average home refrigerator uses 350-780 watts. So, when selecting a solar generator to run a fridge and freezer, it must be sized accordingly.
The last thing you want is for the cooling appliance’s contents to deteriorate because of insufficient electrical power.
Solar generators must be sized not only for the fridge and freezers’ regular running wattage but also for the surge power requirements.
Three elements to ensure a solar generator is correctly sized are the inverter, battery, and solar panels.
You should always assume that bad weather and other factors will affect the solar generator and how long it will need to produce power on battery capacity alone.
Refrigerator & Freezer Power Requirements
Part of the process that causes a fridge to cool down involves compressing and depressurizing refrigerant. Fridges and freezers use induction motors for this purpose.
Induction motors consume two levels of power (measured in watts):
- The power (watts) that are used for the startup or surge power.
- The power (watts) that are used for standard running power.
Surge – Starting Power
When an AC induction motor is at rest and then switched on, it draws a very high momentary current surge.
As the AC induction motor is started, a magnetic field is created in the stator. In turn, this creates a magnetic field in the rotor.
The magnetic fields created in the stator and rotor interact and generate torque that causes the motor to turn.
The biggest inrush current level is developed during the first half of the motor operation cycle. It can be as high as 10 times the full-load current required by the motor. After half a turn, the current is reduced to half this value and finally to the everyday running power.
The Watts Used For Normal Running Power
As the motor begins to speed up, the current it draws reduces until it operates at the rated operating speed. The surge power stops and the standard running power is consumed.
To manage the consumption of several electrical appliances used in the home and businesses, the US Environmental Protection Agency and the US Department of Energy have issued star rating requirements.
The intent is that by conforming to this standard, electrical appliances’ impact on the environment is reduced, and the consumer achieves financial savings.
To qualify for a star rating, refrigerators must demonstrate a 15% improvement in efficiency standards compared to the minimum federal efficiency standard. This is an important requirement for fridges connected to a solar generator.
Calculating Solar Generator Size
To calculate the size of the three main components of a solar system, the following should be accounted for.
But before we begin, I suggest you keep in mind the power requirements of your air conditioner on top of refrigeration.
The inverter is the component most affected by the regular and surge power requirements. The inverter must have sufficient capacity to run the fridge and freezer at the start and afterward.
In addition to providing the normal running power capacity, it must also have sufficient power in reserve to cope with the current to manage the surge power.
The good news is that most solar generators have a surge capacity that is double the regular output.
This means an inverter producing 2kW of power can surge to 4kW.
The solar generator draws current from the battery to power the inverter. There are two considerations in this regard.
Is The Battery Large Enough?
Batteries are rated according to the number of kilowatts they can produce in an hour (kWhs). A 5.1kWh battery could run a fridge that consumes 0.5kW for 10 hours and 12 minutes.
The surge power consumption happens so quickly that it does not have a meaningful impact on the battery capacity.
Battery Depth Of Discharge Percentage
Different battery technologies permit varying depth of discharge percentages. If the battery is discharged to below this value long term, the damage will be caused to the battery.
Acceptable discharge percentages per battery type are shown below.
- Lead Acid, AGM, and Gel Batteries – Discharge to 50%.
- Lithium-ion batteries – Discharge to 15%
- Red-Ox Flow Batteries – Discharge to 0%
Solar Panel Ratings
The solar panel’s sizes (the amount of current they can generate) are calculated to provide the power consumption needed at the peak sun hours at the location.
Peak sun hours are when the solar irradiance (the sun’s intensity) averages 1,000 watts per square meter. Peak sun hours vary by location and season.
If sized correctly, the panels will simultaneously charge the battery and run the fridge and freezer.
To understand this, the following example uses the assumptions listed below.
- There are 5 hours and forty-eight minutes (5.8 hours) of peak sun hours.
- Three 520-watt solar panels are used.
- The fridge consumes 0.5kW per hour.
- The battery has a capacity of 5.1kWh.
The solar panels will produce just over 9 kW of power during the peak sun hours (5.8 hours of sun X 0.520kW X 3 Panels = 9.048 kW.)
The panels will also produce less before and after peak sun hours. In this example, we assume an additional 2 kW are produced during the 1.5 hours on either side of peak sun hours.
The solar panels, therefore, produce 11.048kW (9.048 plus 2.00) per day.
During the 8.8 hours of sunlight (5.8 peak sun hours plus 3 hours extra), the fridge will consume 4.4 kW (8.8 hours X 0.5 kW).
The solar panels produce 11.048 kW, of which the fridge will consume 4.4 kW. This leaves 6.6kW to charge the battery to a full state.
The battery only needs 5.1KWh, so the additional 1.6kW will be used by other consumables or discarded by the MPPT charge controller in the inverter.
This means a full charge is available to run the fridge through the night.
Additional Factors To Consider
There are other factors that you need to take into account.
Unfortunately, the sun does not always cooperate, and there are many days when peak sun hours are not achieved.
This may be due to bad weather, pollution, or the season when peak sun hours are reduced.
To compensate for this, there are three possible solutions:
- Install additional batteries to provide power for longer periods.
- Install a gas-powered backup generator.
- Remain connected to the electrical grid (grid-tied.)
Climate And Temperature Conditions
The climate and temperature conditions have a significant impact on solar systems.
The colder a battery gets, the less charge it can retain. Lithium batteries use chemical reactions to generate electrical currents. Extreme cold can slow these reactions down or even prevent them from occurring.
This will impact how many batteries you choose to deploy in your situation.
Solar panel efficiencies are affected as the temperature increases. It means that the solar panels’ efficiency will be compromised in hot climates with little ventilation.
Recommended Solar Generator Models
The following factors will determine the solar generator that you choose:
- The amount of current that electrical consumers draw on the circuit.
- The geographical location.
- The average temperatures.
- The general weather conditions and amount of sun available.
My recommendations are divided into different categories of solar generators. For all of them in one place, check out my list of the best portable solar generators.
High Power Solar Generators
In the high-power category, I recommend the EcoFlow DELTA Pro. This powerful device generates 3.4kWh of power, increasing to 7.2kWh when a surge is called for.
It has all the necessary AC and DC outlets.
A level 2 EV charger can charge it and will accept a simultaneous charge from an AC power outlet and solar panels.
Impressively, it can be linked to another unit and up to four batteries, at which point it is capable of generating 256kWh.
The unit (with installed battery) sells for $3,299.00.
Best Mid-Range Solar Generator
My recommendation for the best mid-sized solar generator is the Bluetti AC200MAX.
The AC200MAX produces – a total of 2.2kWh, which it distributes through 6 outlets. It also provides DC outputs across several different plug types. It has a surge power rating of 4.6kWh.
It will recharge when connected to a simultaneous AC and Solar power charge in under 2 hours.
The unit sells for $1,859.00.
Portable Solar Generator
Our recommendation is the fully portable Bluetti AC60 weighs 18.9 lbs. (8.6 kg.)
It produces 600 W (surge 1.2kW) and can be extended to 2,015 when an additional battery is connected.
The unit is completely water, dust, and weather-tight.
The model has only just been announced, and prices have not yet been disclosed; however, we estimate it will sell for approximately $500.00
Solar generators that have been sized correctly can run a whole range of appliances and devices and keep critical equipment operational through blackouts.
1️⃣ Refrigerators and freezers consume a substantially higher power level when starting, after which they stay running using fewer watts.
2️⃣ It is vital that the solar generator is sized correctly and that the battery, inverter, and solar panels are sufficient for the task at hand.
3️⃣ When choosing a solar generator, it is also important that the system sizing considers disruptions in solar energy caused by the time of day, bad weather, pollution, or climatic conditions.