# typical power use spreadsheets

2 Posts
Jan 27, 2012 01:49 pm
typical power use spreadsheets

I am trying to design a system that will power off grid 4 apartments.
I sure could use some typical power consumption spreadsheets for single and 2 bedroom units. Or typical loads and run times that could give me a start.
or some ideas that others have used in sizing their own systems.
What real world data could someone help with?
Please anything would be helpful

462 Posts
Jan 28, 2012 12:26 pm
Re: typical power use spreadsheets

Tom, first look at your utility bills to get an idea of how much power is being used then design a system around that. You may find that you will not be able to cover the total amount of power used without spending a whole lot of money.
I would suggest building your system over time. Start small and dedicate  a little power to each unit so each unit, and common places, has some backup and everyday power for emergency use and reduction of power usage. Then, as you save money, add a secondary system and keep going from there.
Using several system setups also adds redundancy in case of failure.
« Last Edit: Jan 28, 2012 12:28 pm by Tom Mayrand »

2 Posts
Jan 30, 2012 09:16 am
Re: typical power use spreadsheets

Very good idea if I were designing a system over time and was going to be in this myself. I am charged with the task of designing a system that is going to be built for someone else. I'm looking for typical loads that will give me a good place to start. My experience is not even near what this assignment must provide.
I appreciate the thought but what I really need is for someone who has seen a few of these systems and would possibly be able to share some typical useage spreadsheets.

462 Posts
Jan 30, 2012 09:43 am
Re: typical power use spreadsheets

Tom, there is really no typical load data for individual systems. Every situation is different. As mentioned, the best way to determine loads is to look at the current and past utility bills.
If you are looking for example spreadsheets, you can find them here at Alte. They have a load calculator where you can punch in some numbers.
Basically, you look at an appliance's power consumtion, figure the Watts then multiply that times the amount of time of usage. For off grid, multiply that by 2 or 3 to determine the amount of storage you will need for times when daylight is minimal.
Then use that figure to find some kind of balance between the number of panels and time of availabe daylight each day.
There are also other sites that offer these types of load calculators, links of which you can find here or at other solar sites like Home Power Magazine and such.....

65 Posts
Jan 30, 2012 10:52 am
Re: typical power use spreadsheets

And just in case you're having difficulty finding the online load calculator on our website that Tom's referring to, it's located here:

http://www.altestore.com/howto/Calculators/c36/

AltE
"Making Renewable Do-able" (tm)
http://www.altEstore.com/

65 Posts
Jan 30, 2012 10:56 am
Re: typical power use spreadsheets

These pages may also be useful to you:

"Typical" power consumption of various appliances:

http://www.altestore.com/howto/Renewable-Energy-Energy-Efficiency/Power-Ratings-typical-for-Common-Appliances/a21/

and our Kill-a-Watt (a meter for measuring in real life the power consumption of various appliances in your home) database:

http://www.altestore.com/store/killawatt/

By the way, anyone can add their real world data on how much power any electric product and model consumer to that database.

AltE
"Making Renewable Do-able" (tm)
http://www.altEstore.com/

99 Posts
Feb 23, 2012 01:46 pm
Re: typical power use spreadsheets

I am trying to design a system that will power off grid 4 apartments.
I sure could use some typical power consumption spreadsheets for single and 2 bedroom units. Or typical loads and run times that could give me a start.
or some ideas that others have used in sizing their own systems.
What real world data could someone help with?
Please anything would be helpful

Assuming firstly that you have no electric resistance heat loads such as electric furnace, electric clothes dryer, or electric stove (which would make the project unfeasible), the largest consumers of electricity will be first a well pump, secondly a septic pump, and thirdly any compressors -- refrigerator, freezer, air conditioner.  If you're on city water and sewer, you can eliminate the first two.  That makes your choice of (EnergyStar or DC) refrigeration appliances extremely important in your calculations of load.  Most other loads are fairly negligible assuming you use LCD televisions and LED light bulbs versus the energy hog alternatives.

You also have to consider peak usage -- what if all four apartments decide to use a hair dryer, or toaster, or vacuum at the same time?  You need to size your battery bank, cables, and inverters to handle that peak load even if the average load is much, much lower.

Also, is someone going to be monitoring this system or is it just supposed to work no matter what?  If someone will be keeping an eye on it, then you can plan to accommodate average input conditions and start a backup generator (perhaps automatically) if the batteries get too low.  But someone has to make sure it stays fueled, unless perhaps you have a city gas hookup or a large propane tank with regular deliveries.  If this is not the case, then you would have to oversize the system to account for low energy input (a string of overcast days if using solar, a string of calm days if using wind).

Also, will all loads be running off an inverter or will you have some DC loads as well?  Remember that conversion takes 5-10% right off the top and certain loads such as compressors or motors may be significantly less efficient on AC (power factor) than DC.

Also, are the people living in these apartments expected to follow certain guidelines, such as don't use a hairdryer or only do your laundry during the middle of the day?  Also, no super-powered gaming computers or window air conditioners.

There are a lot of considerations.  One size does not fit all.  That said, if you just want to over-kill it, go with 4kW of solar per apartment and 1500Ah of battery capacity per apartment (still no electric resistance heat loads or other huge loads!).  That will be significantly more expensive than it likely needs to be though if some of the considerations mentioned above favor efficiency and flexibility.  The low side would probably be around 1.5kW of solar per apartment and 600Ah of battery capacity per apartment.  That's a range I would feel comfortable settling somewhere in between.
« Last Edit: Feb 23, 2012 01:49 pm by Thomas Anderson »

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