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n this series, I’ll cover several important topics surrounding a power or energy budget. What they are, the benefits of having one (especially off grid), and how to create one. We’ll cover calculated power vs measuring it, make some common power measurements to start our online power database, In the last installment we will offer an online calculator to help do your power budget and save energy! . Part 3 described power measurement. In this installment we present some real data that is helpful in creating your own budget, and selecting your off grid appliances.
If you create a power budget based on the information you can get from appliance and device labels, you may be disappointed in the size or limitations of the power system you need to run them. Its very empowering to have a power monitor like the P4400 Kill-a-Watt to get good information about your devices under normal operating conditions. I used the monitor extensively the last week around our off grid home.
[editors note: The entire series can now be found on our new Power Budgets page for your convenience!]
Since it’s winter and we haven’t had a sunny day for 5 weeks, we’ve been getting power in the genverter mode (no solar help), and I was careful to take measurements on inverter power. In our case the inverter outputs a Modified Sine Wave for its AC output voltage. Just to satisfy my own curiosity, I checked many devices on generator power versus inverter power and didn’t see any real power differences.
Please note the data given in the table below can be sorted by any column, or you can use the search feature to quickly find the device you want.
Power Data you can use:
| Device Type | Model / Description | Watts Measured | Max Watts (label) or Volt x Amp | Test conditions / Notes |
|---|---|---|---|---|
| Coffee | Espresso machine, Hamilton Beach | Espresso Machine | ||
| Cooker | ||||
| Computer | ASUS eeePC 1000 Netbook PC | 25W charging 15W operating | 12Vdc x 3A =36W | Charging fully discharged battery. |
| Computer | Desktop PC, Acer xx 4GB ram | 60-75W avg | 110W max measured 120Vac x 7A ~ 840W | power when off = 4W |
| Dishwasher | Kenmore | 1265W | Off Grid Dishwasher? Full load in water miser mode takes 1.37 KWH | |
| Game Console | Nintendo Wii | 17W | Has instant on feature. When 'off' takes 8W | |
| Lights | 18W Compact Florescent, 75W equivalent light | 15 W avg | 18W | 15-16W, when warm 15W. |
| Microwave | Goldstar, smaller oven | 780W | 120Vac x 8.5A ~ 1020W | Heating water for 2 min. |
| Refrigerator | Frigidaire | Refrigerator Power | ||
| Screen | CRT Monitor, 15", old Samsung | 70W | no input 60W | |
| Screen | LCD monitor, 22"Acer X223w | 26W avg | 120Vac X 1.5A ~ 180W | off when off. |
| Screen | LCD monitor, 15", AOC brand | 63W avg | not on label | no input pwr 4W. any input 52W min. Power switch does not affect power, input or not determines power. Max 100W |
| Slow Cooker | Rival Crock Pot (4qt) | 71W Low 140W High | Ran test in Rethinking Off Grid Cooking [1] | |
| TV | Visio 32" LCD flat screen | 70W avg | 120Vac x 1.6A ~ 192W | 90W with no input and blue screen. When TV screen varies from 65-75W |
| TV | Samsung LT2338 | 42W (high pwr save) 62W (auto pwr save) | 100W | Max pwr 78W, use the power saving features in setup menu. |
| USB external Disk | WD 'my book' 500G drive | 7-10W in use | 15W max measured 12Vdc x 1.5A = 18W label | 4W when USB not plugged in. |
| Wireless Router | Zyxel, 4 port | 5W | 12Vdc x 1A = 12W |
Measuring the power yielded some surprising results so far. For example, the fact that many electronic appliances had “instant on” features that drew 3-8 watts, even when turned off! I’ll try to arrange some time with friendly local merchants to take my power monitor in their store and collect even more data!
Free power monitor: This table is not fully complete. We need more types of devices and a few brands of each as well. Want to help? I’ll be giving away a Kill-a-Watt monitor to the 25th commenter on this article! Do you already have a monitor and some information to contribute? Great! Just send it to marshall [at] genverters.com. (Contest will end March 1st with a random drawing for comments if less than 25)
March 2nd Update: Congratulations to Arild in winning the Kill-A-Watt monitor!
Next in this series, I’ll offer an online power budget calculator to help you get a feel for your off grid power needs!
What category of electrical device did we miss here? What do you want listed? Enter your comments below!
Related posts:
Marshall have you ever had the opportunity to measure waveform and power factor of the various gensets you have owned and used? A recent independent genset test was done by Victron in Holland where they found differences in output by various manufacturers. Dick Gee of Alaska Diesel /Northern Lights generator company told me many of the smaller gensets suffered from poor waveform output and had lousy power factor ratings. In my own work we found a 20% improvement when driving the same load such as a small refrigerator compressor by going with a pure sine wave inverter instead of a MSW inverter. I was working as an applications engineer for Xantrex at the time. A certain manufacturer was using our inverter to power their product. I asked if they had noticed any difference between our 1800 watt Prowatt and the 1800 watt Prosine. Turns out they had not even tried a comparison. so I gave them the one from our show booth to test. Test results revealed a 20% improvements in run time when using the Prosine and their compressor ran cooler meaning it would likely have a longer service life.
Assuming your present generator puts out a fairly decent waveform try making power consumption measurements on the same appliance with your inverter and your genset to see if there is a difference.
I do not have one of the Kil-R-Watt meters so cannot say if it responds any different to pure sine wave and MSW. Your remark about the genset running low voltage triggered a memory. One time I had a store manager call up to say we had shipped him a truck load of defective inverters. He said they all read low voltage. Turns out he was using an average reading meter not a true RMS meter. Boy was he embarassed!
At $25 per copy I am wondering if the kill-r-watt reads average or true RMS. I have one of the original TRACE Power meters and it does read RMS which explains why it cost $150 per unit.
Regards
Arild Jensen
Post script to previous post on meter readings. I just did a test on a Xantrex MSW inverter. My true RMS meter read 118.6 volts. My Radio shack meter which is average reading read 100.0V another read 91.3V and one read 84.5 volts. This just illustrates the wide range of accuracies you can find in stores today.All of the meters were made in China. The RMS meter cost $150 while the rest cost under $50.
Arild,
The kill-a-wat monitor indicates RMS values. When running on inverter, it indicates about 118-119 Vac. With my old backup generator charging batteries and running the house at the same time, I read 101-108 Vac since its loaded down and even sounds a little slow.
After Battery bank replacement, comes MPPT charger, and finally true sine wave inverter. I have more plans than $$ at the moment.
Speaking of the true sine wave inverters, do you know if they are quieter as far as RF noise emissions?
Thanks!
Marshall, in reply to your question about RF Noise emissions.Yes sinewave are very much more quiet. We had one ham radio operator complain about our MSW inverter knocking out his ham radio reception. He backed up his complaint with spectrum analyzer readings. We sent him an equeal sized pure sine wave inverter which he tested using the same spectrum analyzer. Apparently he had access to a fully equipped electronics lab. the result was impressive. All the birdies present in the MSW emissions were gone. He reported clean reception on all ham and marine bands. He also tested for noise on the DC power conductors and found them equally low.
One drawback that I later discovered. Pure sine wave inverters tends to trip dock side GFCI as a result of the numerous by-pass capacitors used to supress RFI.
You could probably build a solid little business doing these kinds of budgets for people.
Dave Doolin | Website In A Weekend´s last blog ..Botnet Losing Steam (Under Attack! 2/17/2010)
[...] added the data to the data you can use table. Do you have a newer dishwasher? What are its power requirements? Or, do you have a unique [...]
[...] you get some ideas of what your off grid power needs might be. Don’t forget to consult the data you can use page for some real ideas on the actual power needed by various appliances. If you have something that [...]
On the subject of power consumption by various appliances. The majority of my clients live on inverter power but many are very afraid of propane and despite the power penalty insist on electric cooking. I suspect this comes mostly from the wives but I can’t prove it if they will not admit it. This in turn led me to investigate various countertop cooking appliances. to my surprise many of them proved to use less energy than a regular electric stove and kitchen cookware.
Crock pots also known as slow cookers use 80 – 100 watts and will cook a roast as nicely as a 4 – 6 kilowatt oven but takes longer even if using less overall energy. Induction cook tops much to my surprise heats water to a boil faster than a conventional resistive hot plate and kettle.
Although my wife has demonstrated she can cook on a wood stove or an open fire her culinary accomplishments with some of the electric counter top appliances are far better. she can serve up grilled garlic prawns and a california salad in about 10 minutes using a George Forman grill. 600 watts for 10 minutes is not that much energy. during winter. Using the outdoor BBQ simply isn’t an option when its -20 below and the snow four feet deep. A wood stove is great for cooking stews but only if you like your food chopped into small bits and served as a mish mash slurpy with lumps.