kW, amperes, volts, and kWh: in simple terms (and how to calculate how long EcoFlow will last during a blackout)

In Ukraine, blackouts have become an integral part of our lives, and many people in search of ways to stay connected ask: "Will I have enough?" If you are considering purchasing a charging station, generator, or inverter, you have probably already encountered terms that can be confusing - kW, amps, volts, kWh. Don't worry, we will break everything down and learn to quickly assess how many hours your charging station, say, EcoFlow, will work with your devices during power outages.

Let's start with basic terms. Volts (V) are the "pressure" in the electrical network. In our outlets, it is usually 220–230 V, in cars - 12 V, and some systems operate at 48 V. Amps (A) are the "flow" of current, which shows how much electricity is actually "flowing" to the device. Watts (W) are the power, meaning how much energy the device consumes at that moment. The main formula is: W = V × A.

For example, if your laptop consumes 60 W and operates at 220 V, then the current flowing will be 60 W / 220 V ≈ 0.27 A. This explains why the same device can draw different amps at different voltages.

Now about kW (kW) and kWh (kWh). kW is the power, meaning how strong the consumer or inverter is right now. And kWh is the energy, meaning how much electricity has been stored or consumed over time. To draw an analogy, kW is speed, while kWh is the distance traveled. On your electricity bill, you will see the rate in kWh, not in kW. If the term includes "hour", then it refers to storage or consumption over time (per hour).

On a charging station, for example, EcoFlow, there are two important indicators: capacity (Wh or kWh) and output power (W or kW). Capacity shows how much energy is in the battery, for example, 1024 Wh = 1.024 kWh. The output power of the inverter, for example, 1800 W, indicates what it can handle at the same time. It is important to know that a large capacity does not guarantee that the station will power a high-demand device, and vice versa. For example, a refrigerator may "start" with a higher consumption than indicated.

To estimate the operating time of the charging station, you can use the formula: Time (hours) ≈ Capacity (Wh) / Consumption (W). For example, if you have a station with a capacity of 500 Wh and you want to connect a device that consumes 100 W, you will get: 500 Wh / 100 W = 5 hours. But don't forget that you need to account for losses on the inverter, voltage conversion, and other factors. It is recommended to factor in 10–20% losses, so the actual usable energy will be approximately 0.8–0.9 of the total capacity.

Let's consider a few scenarios. Scenario 1: router + ONU/media converter, which consumes approximately 20 W. With a station that has a capacity of 1024 Wh, you will get: 1024 Wh / 20 W = 51.2 hours. Scenario 2: laptop (80 W) + light (10 W) - a total of 90 W. The calculation looks like this: 1024 Wh / 90 W = 11.4 hours. Scenario 3: a refrigerator that consumes 150 W on average but has a starting current of 600 W. Therefore, it is better to calculate based on the average consumption: 1024 Wh / 150 W = 6.8 hours, but keep in mind that at peak moments it may consume more.

To understand how much your device consumes, look at the label or power supply - it should indicate V, A, W. If only V and A are indicated, you can calculate W: W = V × A. If you don't have this data, the best way is to measure consumption with a wattmeter or smart socket. This will help you find out the actual consumption, especially for refrigerators.

The most common mistakes are confusion between kW and kWh. People buy a station "for 2 kW" and think it will work for 2 hours on 1 kW, but in reality, it may be 0.5 kWh. They also often ignore starting currents, which can cause the station to shut down, even though it seems like it should handle the watts. Do not power a heater or kettle from the battery - it "eats" the charge in a matter of minutes. And, of course, don't forget about inverter losses.

Here are a few quick rules for fast calculations: 100 W load ≈ 1 kWh will last approximately 8–9 hours (considering losses). Approximate consumptions: router 10–15 W, laptop 60 W, TV 80–150 W, LED lamp 10 W, refrigerator "on average" depending on the model. Make your own list of devices with watts and hours - this will help you create a personal plan.

In conclusion, determine your scenario: "internet + light", "working with a laptop", "refrigerator" or "minimal comfort". First, calculate the consumption, then the required Wh, factor in a 20–30% reserve, and check if the output power (W) is sufficient. Don't forget about safety: do not overload the station and monitor the cables.