How many batteries for a photovoltaic system on my house?

Answer 1

If you intend to be totally off-line as far as electricity by using photovoltaic, forget it. The cost alone will kill you.

If you are in an area that will allow it, a combination of several alternative sources of energy are viable. However, none of these are cheap from the get go.Over a long period of time they will probably equal what you spend now for energy.

You need , Solar, battery, hydro-electric, wind, passive etc. all working together if you want to get totally off line.

Keep in mind, the battery system to store the energy will cost a ton. It can be done. Just have to have to correct area with all things working prefect. If you are lucky, you can actually make money but selling the electricity back to the area provider. They have to pay you for it of you are producing it.

Wished I was there but probably will never b.

Answer 2

If you will be off the grid and want to have power day and night, you will need batteries. It is almost certain you would have to shed load when the sun is not shining. You should figure out the ampere hour requirement to run whatever is left on the load during off hours. Let's say it is three kWh at 120 volts. The PV system will probably run on 24 VDC. Three kWh at 24 volts will require about 75 ampere hours from the battery. Problem is that the efficiency of the conversion is not much better than 50%, so you would need a battery of well over 100 AH capacity.

Now you have to think about the size of the PV system. It will have to produce enough power to supply your daytime needs, plus recharge the batteries.

Worse than that, there will be daytime periods when the PV system is not producing much electricity, cloudy and rainy days.

If you are on the grid, You can augment power from the utility with your PV system. Some states allow net metering, so you can feed them power during the day, and get it back at night. More than likely your PV system will not supply all your electrical needs, so you will always have an electric bill.

Having batteries on a grid-connected system is advantageous only during power outages. Unless you have a critical need for power during outages, batteries are not a good idea.

In California, you can't sell power back to the utility. Net metering allows you to bank your daytime surplus with them, and get it back at night. However, if you generate more than you use over a period of a year, they generously accept the excess as a gift. If you use more than you generate, you pay for the difference.