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Running a refrigerator off a solar inverter requires a lot of power. One of the more common questions being asked is, is a 1000 watt inverter enough to run a fridge? Or is a more powerful inverter required? That is what we will explain in this guide.
A standard 14 cubic foot refrigerator uses 1000 watts a day, but it also requires 1800-2000 watts of surge power to start up. A 1000 watt inverter usually has a 2000 surge watt peak capacity, so it should be enough to power the refrigerator.
What Refrigerator Can a 1000 Watt Inverter Run?
Just to be clear, we are talking about a typical kitchen fridge, at least 14 cu. ft. running on 120V. These should not be confused with portable 12V DC freezers and camping fridges. Those are small enough to run on solar panels and batteries alone.
A regular 15 cubic foot energy efficient fridge uses around 100-130 watts an hour. Refrigerators cycle on and off, so assuming an 8 hour on cycle that is about 1000 watts daily.
100 to 130 watts an hour is not a problem for the inverter. The challenge comes with the surge or peak watts. Before you run the fridge on a 1000 watt inverter, check if the capacity refers to the running or surge watts.
If 1000 watts is the running watts, the inverter most likely has enough surge capacity to start the fridge. But if the 1000 figure refers to the surge watts, then it is not enough.
Keep in mind that the 2000 watts must be exclusively available for the refrigerator. Once the appliance starts, its usage drops to 100 watts an hour or so. The rest of the power can then be used by other appliances.
Running and Surge Watts Explained
While a refrigerator may need 1000 watts to run, it usually requires 1800 to 2000 watts to start up. Other appliances and power tools also have surge watt requirements, and though it is only for a second, the inverter must provide it.
Most 1000 watt inverters can handle a 1800-2000 watt surge for a second, which is all a fridge needs. But to be safe you should compare the inverter peak power capacity with that of the refrigerator.
A 1000 watt 14 cu. ft. fridge may require 1800 watts to begin operation, but others may use up to 2000 watts. If your fridge needs 2000 watts and the inverter can only provide 1800, it is not going to run.
The surge watt might not seem like a big deal since it only lasts a second. But without it the fridge will not operate. The good news is most 1000 watt inverters have a 2000 watt surge capacity.
Keep in mind that a 1000 watt inverter is only going to work with 14 to 17 cubic foot refrigerators. Larger units use more running and surge watts the inverter can handle.
Refrigerator Inverter Size Guide
This chart shows some of the most common refrigerator sizes and their inverter power requirements. The inverter capacity here is the minimum needed.
|Refrigerator Size||Running Watts||Starting Watts||Inverter Size|
|14-17 cu. ft.||1000||1800-2000||2000|
|19 cu. ft. frost free||1500||3000||3000|
|21 cu. ft. side by side||1700||3400||3500|
|24 cu. ft. frost free||1800||3500||3500|
|25 cu. ft. side by side||2000||4000||4000|
Some points to keep in mind:
- All the models listed here are Energy Star compliant. Older units (especially before 1996) use much more power.
- The power consumption is the mean average. The power consumption for your fridge may be different. This information can be found on the appliance itself and the operating manual.
- These figures are applicable only to 120V refrigerators. Do not confuse them with 12V solar powered freezers , as they use much less power.
Pure Sine or Modified Sine Wave Inverters
Pure sine wave inverters are more efficient than modified sine wave. With some appliances, modified sine will be enough. But for a typical refrigerator, pure sine wave is the optimum choice.
Refrigerators consume a lot of power, so the most energy efficient inverter is required. A pure sine wave inverter can provide as much as 30% more watts than modified sine wave.
Take two inverters, one pure sine and the other modified sine. Both have a capacity of 1000 running watts and 2000 surge watts. But the pure sine inverter is 95% efficient while the modified sine is only 80%.
A 15 cu. ft. 100 watt fridge will use 105 watts an hour with a pure sine wave inverter, because it is 95% efficient. With a modified sine inverter the power consumption will be 120 watts. That is a difference of 840 to 960 watts a day.
Some modified sine wave inverters have even lower efficiency ratings than that. It can really have an impact in terms of of power consumption. This could also affect the inverter’s ability to supply the needed surge watts.
If your fridge needs 2000 surge watts and you have a modified sine wave inverter with low efficiency, it probably won’t have enough power to start the motor. Even if its peak capacity is listed at 2000 watts, a low efficiency rating means the available power is probably less than that.
It is for these reasons why a pure sine wave inverter is ideal for refrigerators. It is not only more efficient, but these systems are designed to run modern appliances. If you want to use a modified sine wave inverter, get one that has a high conversion efficiency rating.
How Long Can an Inverter Run a Refrigerator?
The answer depends on the fridge power consumption and how much power is available to the inverter. The larger the fridge, the more batteries are needed. If you are on a grid tied system you can run the fridge from the main AC power supply.
It takes six 600ah batteries (with 300ah usable amps) to run a refrigerator for 24 hours. This is only to run the fridge. If you are going to load other appliances on the inverter, it is going to take much more power and more batteries. There is more information about running a refrigerator here .
300 amp hours is about 1200 watts, which is the power consumption of the average kitchen fridge. But this is only for a day. To run the refrigerator every day on batteries, you have to keep it recharged, either with solar panels, a generator or electrical power.
Because residential refrigerators use a lot of power, it will take a lot of battery power. It is possible yes, but you need much more than a 1000 watt inverter. Even if you can get the fridge to run on a 1000 watt inverter and 600 ah batteries, you cannot run other appliances.
If you want to keep the fridge going along with other appliances, a larger inverter and battery bank are required. If you are in an RV, you can always buy a smaller 12V fridge that consumes less power. The drawback is the limited space inside the fridge.
Tips For Running a Refrigerator on an Inverter
If you are going to run a refrigerator on an inverter system, follow these tips to ensure the best performance and cut on costs.
- Buy an energy efficient fridge. All new refrigerators are Energy Star compliant, but some are more efficient than others. Take the time to compare various models until you find a fridge that is energy efficient and has the specs you need.
- Buy a quality inverter. Just like the fridge, go over its specs to get an idea of its running and surge watt capacities.
- Do not run the inverter at its maximum capacity. An inverter can handle peak surge watts for a few seconds a day. But do not force the system to run at its surge capacity for long periods.
- Calculate your power usage. Not just for the refrigerator, but also for everything you will run on the inverter.
Refrigerators have become more energy efficient, but it is still one of the biggest energy users in any solar power setup. The key to running a fridge on an inverter is making sure there is enough running and surge watt capacity available.