# coffee makers not so bad?

Solar Expert Posts: 38 ✭✭
So i found a keurig with a 700 watt heating element. It makes a cup in 3 minutes, with perkeuts effect (however you spell it) and inverter efficiency, thats 70-80 watts for a cup of coffee. That does not sound so bad. I might drink, what 3-4 cups a day, two in the morning and two in the evening? 320 watts over the course of a day, many days my panels power is wasted on topped off batteries. I also see lower wattage 12 volt dc coffee makers that can do it in 5-10 minutes.
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Re: coffee makers not so bad?

Just to make the math work out:

700 Watts * 3 minutes per cup * 1/60 minutes per hour = 35 Watt*Hours per cup

And all the losses back to the solar panel:

35 Watt*Hours per cup * 1/0.52 end to end system eff * 1/4 hours of sun per day = 17 Watts of solar panels

So yes, cooking with solar power can be pretty nice--However, the killer many times is the battery bank:

Using 400 AH for a 12 volt battery bank running a 1 kWatt inverter minimum:

400 AH * 700 Watts / 1,000 watts of inverter = 280 AH of battery bank at 12 volts

Assuming 5% to 13% rate of charge:

280 AH * 14.5 volt charging * 1/0.77 panel+controller derating * 0.05 rate of charge = 264 Watt array minimum
280 AH * 14.5 volt charging * 1/0.77 panel+controller derating * 0.10 rate of charge = 527 Watt array nominal
280 AH * 14.5 volt charging * 1/0.77 panel+controller derating * 0.13 rate of charge = 685 Watt array "cost effective" maximum

A nominal system will generate a minimum (typical, non-winter day) with a 10% array:

527 Watt array * 0.52 system derating * 4 hours of sun = 1,096 Watt*Hours per day from solar
280 AH * 12 volt * 0.25 discharge = 840 Watt*Hours per day from battery (2 days storage, 50% maximum discharge)

So, if your system already meets the above (not a small system)--The sure, why not make a cup of coffee or so with your system.

A 1 kWatt per day system is pretty nice size for a cabin (no refrigerator) with lights, laptop, small water pump, etc.).

Just to make a cup of coffee--Replace the Lead Acid batteries with LiIon of some sort (high current charging/discharging with a small battery bank)--Then it could be very interesting as an alternative source of cooking heat.

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Solar Expert Posts: 38 ✭✭
Re: coffee makers not so bad?

That is entirely to much math for a cup of coffee, my panel efficiency and replacement rate is irrelevant, I already have large parts of the day where i use no power and lots of sun time go to waste and i have about 845 watts of panels and 400 AH usable. Thats for the sake of breathing room say its 65 amps, Still under 50 watts a cup. Thats nothing considering over the course of the day they will top out in a few hours. Even on cloudy days i could probably afford a cup without really putting a dint in my batteries. i dont use near enough to warrant that size of an array. My pump is on once a day for 20 minutes. If i could find a way to build a usable lithium pack i would, the protection and dc conversion circuits are a bit over my head. A battery powered single serve cup would be pretty cool. They do make 12 volt coffee makers.
Re: coffee makers not so bad?

One person here was looking (using?) a solar panel connected directly to a 12 volt frying pan, etc... No batteries, not controllers, just a relatively cheap solar panel and electrically heated frying pan.

An alternative to a solar oven type device.

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Solar Expert Posts: 5,136 ✭✭✭✭
Re: coffee makers not so bad?

I just read over Bills small discussion of a cup of coffee ... If you do not make your coffee till after the sun is well up, you can disregard Bills work, however if you re like the rest of us, rising before they see the sun, that power has to come from the batteries, hence the details bill gave us all... it is a toll on batteries all be it small, it's not just relative to the array size and recharge potential...

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• Solar Expert Posts: 301 ✭✭
Re: coffee makers not so bad?

Apparently more than one coffee a day is not good for ya . . .

First visit too the doctor - he asks me - how many coffee's do you drink in a day ? So I tell him . . .

Second visit to the doctor's he ask's me - how many coffee's do you drink in a day - I now say - too many ..:D

ahhhh . . .. cofffee . . . now even better - solar powered, renewable, green, energy efficient - coffee !
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• Solar Expert Posts: 370 ✭✭✭
Re: coffee makers not so bad?

We have several different types of coffee pots. The most efficient for one cup is our single cup Keurig.

Peak wattage:

Total power used:

Total brew time (in seconds):

• Solar Expert Posts: 8,232 ✭✭✭✭✭
Re: coffee makers not so bad?

I think the Keurig has a preheat chamber that it keeps 1 or 2 cups worth of preheated water, to give you an instant cup when you insert the pod. Check the total wattage from a cold start?
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• Solar Expert Posts: 3,123 ✭✭✭✭
Re: coffee makers not so bad?
mike95490 wrote: »
I think the Keurig has a preheat chamber that it keeps 1 or 2 cups worth of preheated water, to give you an instant cup when you insert the pod. Check the total wattage from a cold start?
Absolutely correct. Since there is no way to drain the chamber, you would have to leave the machine turned off long enough for the water in the chamber to cool completely before testing.
If you leave the unit turned on, most models will turn off automatically. But if they do not, they will kick in the heater occasionally to keep the water hot.
You can also get a fair idea of the draw per cup by measuring the wattage between the end of making a large cup and the time it shows ready to brew again. Then multiply that be at least two to get the cold start wattage.
SMA SB 3000, old BP panels.
• Solar Expert Posts: 963 ✭✭
Re: coffee makers not so bad?

You could plug it in a killowatt meter and run it like normal for 24 hours and see what it does.
gww
• Solar Expert Posts: 494 ✭✭✭
Re: coffee makers not so bad?

I have a cheapy Black&Decker one cup coffee maker. Runs at about 400 watts for three minutes+/-. I run it several times a day, starting in the morning when it is strictly off the battery. I can't really say that I can notice a difference in the system performance. The batteries still hit float every normal day. By far most days are normal days. As long as that happens I don't sweat it.
Northern NM, 624 watts PV, The Kid CC, GC-2 batteries @ 24 VDC, Outback VFX3524M
• Solar Expert Posts: 370 ✭✭✭
Re: coffee makers not so bad?
mike95490 wrote: »
I think the Keurig has a preheat chamber that it keeps 1 or 2 cups worth of preheated water, to give you an instant cup when you insert the pod. Check the total wattage from a cold start?

That's true of the full size Keurig models, but the mini model I showed has no water storage. A cup of water is poured into the machine, the pod installed, cup put in place, then the button is pushed. Only then is the water heated. Once the water has been dispensed, the power draw returns to zero.

My standard Keurig at home will keep water heated all day if you want an instant cup of coffee. Far less energy efficient than the mini model. Consequently, we brew coffee in the morning, then power it off. The mini Keurig lives in my wife's office at work.
• Solar Expert Posts: 185 ✭✭✭
Re: coffee makers not so bad?

My not b your wife's coffee maker recall
http://miniplusbrewer.com/StandardRegister/LPR.asp?L=564&ac=&ar=
Off grid since 1984. 430w of panel, 300w suresine , 4 gc batteries 12v system, Rogue mpt3024 charge controller , air breeze windmill, Mikita 2400w generator
• Solar Expert Posts: 370 ✭✭✭
Re: coffee makers not so bad?
Thom wrote: »

Saw this one a while back, but thanks for the info.
• Solar Expert Posts: 185 ✭✭
You guys got me curious, so I made a 12 cup pot of coffee with my cheaper \$15 coffee maker hooked up to my kill-o-watt meter. 900 watts to a complete finish.
• Solar Expert Posts: 2,969 ✭✭✭✭
You guys got me curious, so I made a 12 cup pot of coffee with my cheaper \$15 coffee maker hooked up to my kill-o-watt meter. 900 watts to a complete finish.

So, you are saying that it took 900 Watt-Hours to complete brewing 12 cups of coffee?? This is a HUGE amount. Is it possible that this is just the power to run the coffee maker, not the accumulated Watt-Hours?

This would seem to imply that the process required about 45 minutes or more. The standard coffee makers that I've seen require about 1000 Watts, 1200 W tops.

Will try to remember to check my maker, although, usually only brew four-ish of their "cups". FWIW, Vic
Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
• Solar Expert Posts: 185 ✭✭
Probably took less than 15 minutes with the coffee maker plugged into the watt meter. 900 watts just for the coffee maker to brew 12 cups, but not maintain the temp. Yes it is a bunch. I guess I need to install my other 10, 200 watt panels soon.
• Solar Expert Posts: 2,969 ✭✭✭✭
Finally got around to measuring how much power it takes to brew 4.5 (of their) cups of coffee -- about 16 oz of coffee produced. Required 70 Watt hours, and the maximum power taken from the AC line was about 865 watts.

Well worth the power, IMO. Vic
Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
• Solar Expert Posts: 1,278 ✭✭✭✭
This probably goes without saying. If your coffee maker has a hot plate to keep your coffee hot you can/should use a vacuum coffee carafe instead. Once your finished brewing just transfer finished coffee into the carafe and turn off coffee maker. FWIW

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• Solar Expert Posts: 3,009 ✭✭✭✭
BB. wrote: »

So yes, cooking with solar power can be pretty nice--However, the killer many times is the battery bank:

-Bill
.
Which is why my battery bank is as big as it is. It's extremely satisfying to cook with solar. Yes, the system and batteries cost money, but so does smoking, drinking and owning boats for "fun". 8) Reminds me, time to start the breadmaker. Yes, it's cloudy, but there's still plenty of power to make a loaf of bread.
• Solar Expert Posts: 626 ✭✭✭
Yeah the kuerig is cheap on wattage, but man, oh man, those kuerig cups are expensive compared to buying whole beans and grinding them yourself with good old Mr.Coffee.
• Solar Expert Posts: 3,009 ✭✭✭✭
Yeah the kuerig is cheap on wattage, but man, oh man, those kuerig cups are expensive compared to buying whole beans and grinding them yourself with good old Mr.Coffee.

And I've heard the "inventor" mention how they turned out to be bad for the environment because of the waste and disposable containers.
• Solar Expert Posts: 626 ✭✭✭

And I've heard the "inventor" mention how they turned out to be bad for the environment because of the waste and disposable containers.

Yeah they use the non-bio degradable cups, VS the synthetic vegetable oil cups, because the synthetic cups melt when making contact with the hot water. Also the synthetic cups cost 30% more to make, so the inventor that sells the licensing rights makes less, keurig make less.

I have noticed though, because my girlfriend loves her Kuerig, there are some "off brand K cups" that come in white synthetic instead of the standard black non bio degradeables. The cups are slightly thcker in mil so they don't melt so fast.

Me personally though, I don't mind burning an extra 80 watts with Mr.Coffee, another 40watts with my coffee grinder, and grinding whole bean peet's coffee. I love the freshness and all that oil that sits on the top of my coffee. Nothing comes close.

2lb whole bean bag is 60% more cost effective than buying 24 or 42 K cups.
• Solar Expert Posts: 4,413 ✭✭✭✭✭
An electric coffee maker in an offgrid home is a discretionary load. After 3 ? bad winter days one must prioritize energy use. A propane kettle of water works well. Learning to use 4 KWH to 40KWH per day is a seasonal issue.
Some would give up lighting in the home for electric coffee. I get that ! I would use propane myself !
"we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
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• Solar Expert Posts: 3,738 ✭✭✭✭
And I've heard the "inventor" mention how they turned out to be bad for the environment because of the waste and disposable containers.

The coffee growers don't like the K cups either. Their reason is that the K cups depress coffee prices. It turns out that as more folks use K cups, coffee demand goes down. This is because most folks with coffee pots brew (and often drink) more coffee than K cup users.

--vtMaps
4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
• Solar Expert Posts: 494 ✭✭✭
I'm with Dave. We use both an electric coffee maker and an electric kettle for tea. But if the weather tomorrow is like it has been since late Saturday we'll be using the propane range.

Edit.... looks like the generator will be running. So we'll still have electriccoffee. We've had the pv disconnected all day because of lightning and the forecast is more of the same tomorrow. Don't mind the rain, but sure don't like the lightning even with all the protection
Northern NM, 624 watts PV, The Kid CC, GC-2 batteries @ 24 VDC, Outback VFX3524M
• Solar Expert Posts: 5,124 ✭✭✭✭
edited October 2016 #27
Just to revive an old thread.  In my situation, I have used propane (or wood) for years, but since PV has gotten so cheap, I now have a significant daily excess of power 9 days out of ten.  (I now have over 600 watts of PV, and just got gifted 450 more that I installed in another building.) ( And accordingly, to prove Icarus's second law of off grid living, that is, "loads always grow with time.." Our daily use is now closer to 1kwh up from .5kwh. )

My issue with propane is not the cost per se, but for me getting it is a major hassle.  We are 150 Kim's from town, and you can only transport propane in Canada in an open vehicle, and carry only three tanks.  Additionally, I am 15 miles down the lake in a small boat (or snow machine in the winter) so I have to wrestle tanks around and...I'm getting old(er)!  The idea of using an Mr. Coffee type machine is very appealing.  We already put the coffee into an insulated carafe, and cover that with a thins ulnar toque (hat to you southerners!) and it keeps the coffee hot till mid afternoon.

So has anyone ever found a lower wattage Mr. Coffee machine, say under 600 watts?  I still only have the 300 watt inverter and don't need to spring for a bigger one just for coffee.  (Although I'm on the hunt for a magnum mms 1012 if anybody has a spare!). The Sursine 300 will do 600 watts for 1/2 hour.  My wife just started using a small electric steam iron for her sewing projects when the wood stove is not on, simply because it makes more sense than the propane.  The Suresine runs it just fine, and the batteries don't even breath hard for the duty cycle.

Tony
• Solar Expert Posts: 4,413 ✭✭✭✭✭
edited October 2016 #28
Good to see you back Tony !  The basic offgrid unit of power is going up also. I use to think a 500 watt gas oven with a glow bar was my design limit for deep winter. Now it is 1500 watts cycling a Pizzia oven. I probably could help with the magnum from my dealer but it would be an issue with shipping/duty I think. Good Luck
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• Solar Expert Posts: 106 ✭✭
• Solar Expert Posts: 2,171 ✭✭✭✭
For a small time, I delighted in making coffee with my small, new, and affordable convection stove pad. Then a couple things happened:
1) Realized that an 8 gallon propane tank provides me with enough cooking fuel to last for several months....at a cost of \$8. If I get my large propane tank filled before September, propane costs \$1/gallon. They charge about \$2/50 gallon for filling small tanks. Being able to do it yourself saves a lot of money and becomes very convenient. Used to make a lot of propane buying trips. Having several hundred gallons of propane = piece of mind as well.
2) I do breakfast when the batteries are at their absolute lowest....right before sun-up. Thus adding insult to injury. A wise solar enthusiast, which I aspire to be, designs their greatest energy usage to coincide with greatest energy production.
First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
• Solar Expert Posts: 494 ✭✭✭
Cold brew coffee uses no electricity at all.  We have an OXO brewer. For those who are also bothered by the acidity of regular hot brew coffee cold brewing reduces the acid content.
Northern NM, 624 watts PV, The Kid CC, GC-2 batteries @ 24 VDC, Outback VFX3524M