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Martin Webb: Understanding your utility bill

Lately there's been an awful lot of chit chat about utility bills, and it turns out I happen to be an expert on the topic. I have brought together information that I think will improve understanding of utility bills and how to read them, along with other energy options.

In this column you'll learn about some basic definitions that are required to help understand your PG&E bill and electricity use.

There is a lot of confusion surrounding these three basic terms/units: watts (W), kilowatts (kW) and kilowatt-hours (kWh), as well as confusion about digital meters vs. SmartMeters vs. analog. Here is how to understand the difference, which is fairly easy to grasp if explained right.

WATTS (W) — Everyone's generally familiar with watts as a unit of power. Light bulbs come in watts: 40W, 60W and 100W. That's how much power is required to turn the item on. If a light bulb is rated 100W and you can only supply 5W to it, then it won't turn on. It requires 100W of power to run, and it will consume 100W continuously while on. For example, if you have 10 100W light bulbs on, then your home will be consuming 1,000W of power all at once.

KILOWATTS (kW) — This one is pretty simple. A kilowatt is just shorthand for 1,000W, just like a kilometer is 1,000 meters and a kilogram is 1,000 grams. So if you are consuming 1kW, that means you are consuming 1,000W. This is important to know, because all the digital meters that were installed over the past few years have a pretty cool feature that was never available before to homeowners, back when we were all using the analog dial meters.

If you go out and look at your digital meter, the screen scrolls through various sets of numbers, showing one number for a few seconds and then switching to a different number. Not all digital meters show the exact same info or in the same order, but they all will show one very interesting data point about your home that can help you understand your power use: how much power your home is cumulatively using at that one moment.

Watch the meter as the display scrolls through the data points, and one of them will usually have a small "kW" on the screen during one of the numbers. For example, I recently checked the meter and saw the number 1.09, and underneath it a little tiny "kW." This number means that, at that moment, the home was consuming a combined 1.09kW, or 1,090W.

So if you went inside and added up all the items that were on, they totaled a combined 1,090W altogether.

While you stand there and look at that number, it will likely change every time the screen comes back to that data point, as home power use is constantly changing. Refrigerators are turning on and off, cycling through keeping the right temp inside. Lights are turning on and off. HVAC fans turn on and off as the heating or cooling system cycles off and on to keep the right temp in the home. A faucet turns on for a few seconds and a pump runs for a few seconds.

Homes in our area typically will show 1,000-2,000W being consumed (when folks are home) all at one point in time, but everyone is different and homes vary quite a bit.

But remember, your PG&E meter will show this number in kW, so 1,000-2,000W will look like 1.00 to 2.00 kW on the screen.

Martin Webb has worked in the solar industry for nearly 20 years, currently solar sales manager at Byers Solar. He hosts a monthly energy report on KVMR community radio 89.5 FM. This series will continue with more discussion of energy use and how this relates to your energy bill. Email questions concerning solar to Webb at, or call him at 530-272-8272.