Martin Webb: Meter reading and your home
June 9, 2017
If you want to better understand your energy bill, here's some homework for you: if you leave home and go out (turning everything off inside before leaving), once you return and before you go in, walk over to your digital meter and check out how much power your home is using with no one inside.
You may be surprised.
Ideally that number should be as small as possible, but in today's world we know that much of our appliances still use power even when "off."
A study done at Lawrence Berkeley National Labs showed that when you look at common items like DVD players, TVs, stereos, etc., over the lifetime of the unit more power is used when it is OFF than when it is ON, because they are OFF more than they are ON, and that small steady power draw adds up to more power than the total lifetime power used when ON. Crazy, huh?
That's why you may wish to have all those types of items on a power strip that gets turned off, meaning no power is consumed when off. (Note: If these items have a clock function, this will mean the clock will keep resetting.) I have my TV, DVD player, and speakers all plugged into a power strip that stays off. When I need to run them, I flip the strip on and then turn on the items. When I'm done, I turn off the items and then turn off the power strip.
So here's what you may also do: use the digital meter screen to assess how much power you use at different times of day, and how much power each different appliance uses. Once you return home and check the power being consumed with no one home (I hope it's 100-200W or less! Which would appear as 0.10 or 0.20 kW … basically take that reading in kW and multiply by 1,000 to convert to W), and then go in, turn everything on, and go back out and see the difference. If you have a hot tub and want to know how much power it actually uses when on, go read the meter before it's on so you have a baseline, and then turn the spa on and go back to look at the meter.
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I did this recently for a homeowner who said, "Well, we don't run our hot tub, but one of the reasons we want to go solar is to run it, so how much more solar would be required to run it? Please take our current use and add the hot tub."
So I explained the meter readings to him and while he and I stood at the meter, his wife flipped the tub on and off.
Before? The meter showed the home consuming about 1.00kW. After? 5.00kW, (we turned it on and off to verify it wasn't other items). That hot tub used 4,000W when it was on!
How much does yours use? Is it really big and old, or is it small and brand new? There can be a huge difference. You can check out all of your major power draws this way: use the "instantaneous power draw" meter reading — you!
OK, here's where the rubber meets the road with your PG&E bill, because utilities bill you for the total kWh used in a billing period … not W or kW. The difference? Kilowatt-hours are a reflection of how long an item is on and consuming power.
For example, if you have a 1,000W fridge, meaning it needs 1kW to run (remember 1,000W = 1kW), and if it runs for one hour solid, then you just used 1 kilowatt-hour, or one kilowatt for one hour. If that 1kW fridge runs for 2 hours, then you just bought 2kWh. If that 1kW fridge runs for half an hour, then you used 0.5 kWh.
This also means that a 4kW appliance (let's say a huge shop too … or that big old hot tub!) that runs for an hour will use 4kWh. A 4kW appliance that runs for half an hour uses 2kWh. And a 4kW item that runs for 15 minutes will use 1kWh.
So a 4kW item that runs for 15 minutes uses the same amount of energy as a 1kW item running for an hour, both will come to 1 kWh. This is important to know, as your PG&E bill is based as much (or more) on how long things run, not just how much power they draw.
This series will continue with more discussion of energy use and how this relates to your energy bill.
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 is the second story in a series that will continue with more discussion of energy use and how this relates to your energy bill (See this story online for a link to part one). Email questions concerning solar to Webb at Webb@thatsbyers.com, or call him at 530-272-8272.
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