Having wasted both time and money on small systems let me throw out some ideas. Three rules. It takes far more equipment than you would think, it will cost far more than you think, and it will never, ever break even compared to electricity or using portable generators.
When you talk about off grid, that never means having the luxury like you have in a regular home. I understand your concern is fridge and freezer, your ultimate play will be to run the fridge 7 hours, shut it off and run the freezer one hour. Every spare inch of your freezer will be filled with ICE, frozen gallon jugs is good, it is water if you need it, and it keeps the mass colder than air will. Some considerations have played with it for years.
First, do not even think about using the battery, solar or wind power to heat anything. It takes too many BTUs. You mentioned heating water. Bad idea. Electricity supplied by batteries should never be used to heat anything. If you are talking about an electric home water heater, they will zap your batteries. Even when calculating the power needed to run one on a portable generator the general rule is: A 5,000 watt generator is capable of running a electric water heater, but caution should be taken not to exceed the generator’s total 5,000 wattage rating. A electric water heater needs 4,500 watts to start the appliance and 3,500 watts to continue powering the heater. So, if that is the plan, it too should be put on a timer and the fridge and freezer turned off while it heats up.
One suggestion I have for off grid water, is the propane heated instant water heaters. Usually called the tankless water heaters, you still must have water pressure, a small propane tank and batteries, then hoses run to a portable shower. They could also be piped right into the plumbing side by side with the existing water heater
Second, batteries are not what you think. The only rational batteries at a decent cost for your planned use are golf cart batteries. Let me talk just a second about the whole concept. You will need deep cycle batteries, do not get stuck with the new technology yet. You need to know exactly how much draw your older appliances draw. You mentioned a 10KW system, that is a lot for the cost compared to alternatives.
Do not trust any of the articles you read about how much power your fridge or freezer will use and do not believe the label on them. For about $40 you can buy a device called the "Kill-o-Watt" that you plug into the wall and your appliance into it, and it tells you exactly how much power your unit it using. Most will use more as they age, seals leak, etc. You have to measure everything you want to put on the back up power, everything. Alarm systems, motion detector lights and everything draws electricity, if it is plugged in.
Your refrigerator takes up to 1,200 watts to start the frig every time it starts, but then may only use 500 watts or less to run, assuming Energy Star everything. The freezer the same way. In an emergency, you should plan to put them on timers, the freezer only needs to be on every few hours, you do not want both of them trying to start at the same time, so you put the on timers.
When you say a 10KW system, I assume you are planning for things like a weather outage? If so, you can never plan on having solar when the weather is bad, bad weather means clouds, rain, snow or other, but not bright sun. So, if solar and batteries are for bad weather, you will need enough battery to run 4-5 days with zero sun. Then if they get to zero, it may take a day or two before they have the start up power needed for each appliance. Like the has water heater, it take a lot.
We live at the dead end of a rural line and use the generators 1-3 times a year, sometimes several days. The smartest and most cost effective thing is a generator, a multi-fuel is great. That way you can buy a couple 40 gallon propane tanks and 5-10 gallons of gas and be set for a very long time. You never worry about the wind or the sun. Generators are easy to maintain and cost zero 99% of the time. A solar system has batteries that are losing their value every day and about year 5 will have to be completely replaced. Small portable generators will last a lifetime. I have 4 generators and use them for many things. The little 4,200 watt from Cabelas and the 3,800 KW Champion just run and run and run. The Champion is over 20 years old and shows no signs of slowing down. Just change the oil every few years and filter and run clean gas in them, and will last a lifetime. I actually run a couple 50 foot coords from outside thru my house when needed. I alternate the fridge and freezer and run my whole house central heat with no problems. It will run the AC summer or winter, I have propane heat.
I put together a system using Harbor Freight 45 watt panels. I only use them for lighting and radios and light duty stuff, the cost of batteries is just too much. To give you an idea of cost, Lowes sells a plug and plan solar kit, it supplies 1,240 watts, nothing close to your 10,000 watts. The cost is $6,700.00. Here is the kit.
OVERVIEW
Plug and play solar.
- Off grid plug n play solar system with 1500 watt supply inverter ideal for small size remote cabin
- Includes 2 batteries and additional batteries can be added later
- Pure sine wave inverter
- Adaptable installation that can be mounted on the roof or on the ground
- Quick tilt adjusting mechanism for maximum solar energy production and easy snow removal
- Smart finish, aluminum and galvanized steel for that elegant and efficient look
- High energy production at low cost
- 4 solar panels with total solar power storage 1240 Watts or greater
- 25 year manufacturers limited warranty on solar panels and 1 year on inverters,1 year on workmanship
Installation ManualPDF
SolarPod Portable Solar Power Kit in the Portable Solar Power Kits department at Lowes.com
Anyway, my take is there is no cost effective way for us to use solar for short term emergencies. It is just much more cost efficient to let the food spoil. I actually had a freezer go bad while gone once, it was full of elk and venison. My insurance did reimburse me a bunch on it. I had to throw away 80 pounds of elk. Pretty sad deal for sure.
