When we get our electricity bills, it shows that we have used a certain number of units for the given period. When we go to buy appliances, most of them have watts mentioned on them. If you find it difficult to understand the relation between the two, then you are not alone. Electricity bill and its components are confusing to many and with this article we will try to explain what are watt, kilowatt and a unit of electricity. Power and Energy/Electricity are two words that are used so much for each other that many feel that they mean the same. Interestingly both of them have a very different meaning. Power is the rate at which electricity is used and energy/electricity is the actual consumption. To give an analogy, power is similar to speed but electricity/energy is the actual distance travelled. So        Power x Time = Electricity (or energy) Just like          Speed x Time = Distance Travelled. Power is always represented in watt (W) or kilowatt (kW).

A thousand (1000) watts make one kilowatt. So if any appliance is rated as 1.2 kW then it means that it consumes electricity at a rate of 1200 W. Now as we discussed earlier that power is the rate at which electricity is consumed and not the actual electricity consumed, Watt or Kilowatt just represent the rate at which electricity is consumed per hour. Which means that when you buy a 100 W bulb, it does not consume 100 units of electricity but consumes at a rate of 100 W. A unit (as mentioned on the electricity bills) is represented in kWH or Kilowatt Hour. This is the actual electricity or energy used. If you use 1000 Watts or 1 Kilowatt of power for 1 hour then you consume 1 unit or 1 Kilowatt-Hour (kWH) of electricity. So the reading on the electricity meter represents the actual electricity used. Just like the odometer on your vehicle that shows the actual distance travelled by the vehicle, electricity meter shows the amount of electricity that is used. So a 100-Watt bulb if kept on for 10 hours will consume:

100 x 10 = 1000 Watt-Hour = 1 Kilowatt-Hour (kWH) = 1 units (on your meter). Now with most of the concepts explained we would like to make it easy for you to calculate how much units does any appliance consume. Most appliances have wattage written on them (either on their container box or somewhere on the appliance). Once you have the wattage, next you need to figure out how many hours a day do you use it. After that you can use the formula below:prices for hvac systems Daily Units = (Wattage x Usage hours per day) ÷ 1000ac window unit is not cooling Monthly Units = Units x 30 (or 28,29,31 based on month)window ac unit temperature Please note that this formula may not work always. For appliances like Air Conditioner, Water Heater, Cloth Iron (any heating or cooling device) and pumps, this will not work.

Also check this video that can help you understand how many units your appliances are consuming: In my house I have 3 small air conditioning systems running at 8000 BTU/hour each. I would like to power them with solar energy. I found that I would have to generate: 3.41 BTU/hr = 1 Watt 8000 BTU/hr = 2346 Watts That means to power the 3 units for 4 hours/day, I would need (2346 Watts* 4 hours/day * 3) = 28152 W*hours/day, or approximately 30 kWh/day. I checked that in my region, I have 7 hours of sun each day. So to generate 30kWh/day, I will need something like 5kWh/hour = 5000 Watts. Are these calculations right? Going further, I'm able to generate now (i have 4 * 250 watts solar panels) 1kW, but I generate it 7 days per week, and I use the air conditioners, maybe 2 times/week. Thinking in this scenario, I don't have to be so concerned about how much energy can I generate hourly/daily, but weekly right? Another important point here is the batteries where I will store the generated energy right?

Any suggestion which kind of batteries set should I use? Actually your AC is much more efficient than that because it is a heat pump, not a direct conversion of electrical watts in to BTU of heat moved per hour. If you know your SEER rating, you can just divide the BTU/h by SEER to get Watts. An SEER of 10 is very common so that would mean each AC needs 800 W to move 8000 BTU per hour. BTW, it's good to keep your units straight between energy and power (which is the rate that energy is being used). Watt-hours and BTU are energy. Watts and BTU/hour are power. And your AC is not 8000 BTU, it's 8000 BTU/hour. Cannot answer #1 or #3 but WRT #2, with intermittent usage you want enough storage to last you approximately 2x to 3x your longest period of A/C use without sufficient light to generate the necessary power. Usually this will be at night - but depending on where you live it also might be on an extended period of hot, rainy days. For instance, recently in Maryland we had over a week of 80-90 degree days with POURING rain and 100% humidity.

Just wondering - instead of going with batteries, can you go solar-on-grid, where your excess energy goes into the grid (and you get paid for it) and when your solar isn't generating enough, you can draw from the grid?Browse other questions tagged air-conditioning solar-panels alternative-energy or ask your own question.Knowledge Base : Tools : Calculator | DC to AC amperage conversion run through an Inverter So, you’ve got an electrical appliance to run, but no place to plug it in. When you need to run a regular household electrical type device in an area where no regular grid power is available, this calculator will help you figure out what size batteries and inverter you need! Welcome to our DC/AC conversion tool (with inverter). This calculator is designed to assist you with power usage amounts, when converting from one power form to another using a DC to AC inverter. Just enter power numbers in the fields below, and we will do the calculations for you, including typical inefficiencies and all that other techie type stuff you may not care to calculate.

If you are not sure of your numbers, have a look at the walkthrough illustrations below when entering numbers. Enter AC Device Ratings Amps AC (enter mAh as .xyz) 12 V     24 V     36 V     48 V Many applications will have a range of Input AC voltage. In the US, it can be anywhere from 100-125 VAC. In Europe, it's usually 200-240. For this example, we'll use the US standard of 120 Volts AC. Input Amperage is how much current the application draws from the AC power. This number is usually rated in Amps. If the current is rated in milliamps (mAh) you can convert it to Amps by diving the number by 1000. For instance, our example application draws 300 milliamps, which is the same as 0.3 Amps. Wattage is the total amount of power the application uses. It's calculated by multiplying voltage by amperage. Therefore the 120 VAC x 0.3 Amps equals 36 Watts. Output Voltage is rating of your battery system, usually a single 12 volt battery. We use 12.5 volts for 12 volt battery systems.