Home Solar Power with Batteries and/or Generator

Last updated on May 12th, 2018  

Please read the basics of low cost  Solar Home Power if you have not already done so.

Here I discuss the additional complications of batteries and generators.

I am also focused on living judiciously. That is trying to minimize costs.

The fact is you could buy a big generator and a big fuel tank and have all sorts of power on demand but this is very costly and frankly not worth it.

The problem is that you really do not need that much power and a big generator just wastes a lot of fuel.

I also assume you are trying to power a basic family style living situation and that you are heating your home with something other than electricity.

With those caveats in mind let us continue.

Batteries do not last very long. 7 to 15 years would be lucky.

Lower cost batteries need to be maintained. Higher cost batteries can reduce the monthly maintenance but often have shorter lives.

Yes the lower maintenance batteries are both more expensive and have shorter lives.

The major components that make up your off-grid or grid-tie solar electric system are:

 1) grid-tie & battery capable inverter
 2) panels
 3) batteries
 4) generator

A good base system is 4000 watt solar electric system, 4 or 8 Surrette S460 batteries, and a Honda EU2000isa generator.

The Honda EU2000isa is a manual start. I know you want an electric start but they will use a ton more fuel. If you find a 2000 watt electric start generator let me know and I would be happy to look into it.

By the way, you would be much better off running your generator on Propane or Diesel. Storing gas around your home is much more dangerous than storing Diesel or Propane.

Also gas goes bad quickly so you will have to treat it with fuel stabilizer. Diesel should be treated also. Propane does not need stabilizer.

Champion makes some dual fuel propane/gas generators in the 2200 watt range with electric start. They will still use a lot more fuel to run your home than the Honda EU2000 generator. I explain why shortly.

If you purchase standard lead-acid batteries you will have to add water to them every month or two. That consists of removing little twist on caps and adding distilled water up to the fill line.

If you allow a standard lead-acid battery’s water level to drop below the metal plates the plates will immediately corrode and the battery will be destroyed. The effect is immediate. Do not allow the water in lead-acid batteries to get low.

Next toss out all your energy hungry appliances. Old appliances use a ton more power than newer appliances. Some just burn away power because they can for no good reason.

I have a relatively modern Panasonic microwave and it chews up 20 watts just being plugged in. This is ridiculous. It has other dumb problems operating off grid, so I suggest staying away from Panasonic. Speaking of microwaves make sure to get an Inverter style.  Inverter style microwaves can be much less stressful on your generator

It is far better to make your home more energy efficient than it is to create a bigger power system.

Buy lower power appliances and preferably ones that are entirely off when not in use.

Get a refrigerator that uses less than 400 kWh per year.

The key is to size all your appliances so they will end up working if you are stuck running on your generator for days on end during bad weather.

If you generator is 2000 watt try to keep each appliance limited to 1000 watts typical power consumption.

You want to pick appliances that are low energy consumption **and** energy star rated.

You might have noticed your Honda generator has a 1 gallon gas tank, which will not last terribly long. You can add a larger external gas tank fairly easily,

You will also need to change the oil in your generator every 100 hours which is every 4 days if you are running on the generator 24 hours per day due to bad weather.

You will need to check and possibly change the spark plug in the generator every 300 hours.

So operation is pretty simple:

Run your solar electric system and charge your batteries.

When the battery power gets low start your generator.

What kind of typical power demand does one see via modern energy star appliances?

                       typical surge
20cf   fridge/freezer  100     1500
washer                 250     750
dryer (gas)            250     1000
microwave (1000)       1000    1000
coffee maker           900     900

“Surge” is something that occurs when an appliance first turns on. “Typical” is what the appliance really consumes while it is operating.

With a Honda EU2000isa generator, which really produces at most 1600 watts, you will not be able to run your microwave and coffee maker at the same time.

With a Honda EU3000isa generator you would be able to. And you would have electric start too, but you would be wasting far more fuel.  How much more?

Here are some helpful numbers:

               real
Make           watts MRH Gallons   GPH    GPD   GenCost
               
Honda EU3000is 2800  20   3.4    0.170    4.0  $2300
Honda EU2000is 1600  8.0  1.0    0.125    3.0  $1000
Champion       1700  9.5  1.0    0.105    2.5   $470
Honda EU1000is  800  7.1  0.6    0.085    2.0   $800
igen1200       1000  10   0.8    0.080    2.0   $380

MRH = Max Runtime Hours at reduced load
GPH = Gallons Per Hour
GPD = Gallons Per Day

You can think of the GPH number is the relative efficiency. Lower is better.  You can multiple the GPD number by the cost of gasoline to get a sense of how much money you would be spending for fuel.

Another way of getting along with a minimal number of batteries is to avoid using energy intensive appliances when the sun is not shining.

This is actually the opposite of what most people do.  Many want to run energy intensive appliances when it is raining such as doing the laundry or vacuuming the house.

Putting energy into your batteries and taking it out again is not a particularly efficient process.  You lose a fair amount of energy putting it in and taking it out.  Thus using the energy before it is put in the batteries (when the Sun is out) uses much less total energy.

Putting the energy into the batteries and getting it back out generally consumes about 30% of the energy leaving 70% for running your appliances.

On the other hand, if you run the appliances directly “off-the-sun” generally you get to around 95% energy efficiency.

Using a manual start generator means you have to pay attention to power usage and start it when needed.

The big advantage of electric start generators is that some inverters will control the generator for you, or you can get small generator controller that will start the generator when the battery power gets low.  Thus you do not have to pay as close attention to your power usage.

On the other hand, you do have to pay attention to your fuel consumption. Most smaller electric start generators have a 5 gallon gas tank, which you will need to check and re-fill as needed.  You can also add an large external gas tank which will allow you to check less often.

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