A Low Carbon Life | Post 6 2018 | Electricity & Appliances
Over the weekend my friend HC asked me how she would know if the solar panels she is thinking of installing would have enough power to run her kettle and toaster at the same time.
If she goes ahead with the install, then she will put on 2kWs of panels or 2,000 watts (1,000 watts equals 1 kilowatt abbreviated to kW). Powering appliances versus the amount of electricity we use, and hence pay for, is something that took me ages to get my head around and I was really pleased that she asked me the question – partly because I can answer it and partly because it’s good to know that I’m not the only person who struggles with these ideas.
Here is an example of how to calculate the power that an appliance needs:
The first image is of the bottom of our kettle (sorry about the quality). You can see on the far right side of the power plate that it says 2400W. This means it needs 2400 watts to run or 2.4kW. If you run it for an hour, then you will use 2.4kWh (2.4 kilowatt hours); if you run it for 5 minutes then you will use 2,400 watts divided by 1/12 of an hour (5 minutes) = 2400/12 = 200 Watt hours = 0.2kWh. So, it won’t turn on unless it has access to 2400 watts and if you then run it for 5 minutes it will use 0.2kWh.
Here is the same example with our toaster.
The power plate says it uses 1800 to 2000 watts to run, which is 1.8 to 2.0kW (say 2.0kW). If you set it to toast for 2 mins (1/30 of an hour), then is uses 2000w/30 = 67 watts or 0.07kWh but you still need it to have access to 2.0kW to work.
If HC’s toaster and kettle are the same as ours, and she wants to turn them on at the same time, then she needs 4.4kW of power available. With her planned 2.0kW system, she hasn’t got enough power so she would have to draw power from the grid to get them started together.
Clear? Try the calculations yourself with your own appliances. It took me ages to get my head around this and I like mathematics so I feel for people who don’t like numbers!
‘I Care’ so ‘I do’. Until next time, Jane