If your household uses 5kw of electricity in a month will a 5kw solar (pv) system supply your needs? ?

Question

If it doesnt add up that way, how does it?

Answer 1

Scottsdale's answer is pretty good, but I haven't seen a net metering system that will continue to maintain power when the utility goes down, unless the system has batteries.  My system will not do that.  The problem is that the inverter would not provide proper voltage if the load exceeded the solar output.  This could happen, let's say in summer when the air conditioning and other loads are greater than the solar system is generating.  Also it might have problems if the solar output greatly exceeded the load at any given time.

Answer 2

Your are mistaking power in kilowatts (kW) for energy which is measured in kilowatt-hours (kWh).  You need to determine how many kilowatt-hours of electrical energy you use per month.  From this you can get the energy usage per day or it might be directly printed in your bill.  

For approximate calculations, you can assume that a PV panel that has a peak power production of say 1 kilowatt will actually produce an average  of one sixth of that measured around the clock for every day of the year.  That means that a 1 kW panel really produces a 24X7X365 equivalent of 167 watts continuously.  This means that the 1 kW panel produces 24 X 167 watt hours of electrical energy per day.  This is approximately 4 kWh of energy per 1 kW panel per day averaged through a whole year.

Now, divide your daily energy usage in kWh by the 4 kWh figure above to determine how many 1 kW panels you need for your system.

These are minimum calculations assuming that you want to produce the total energy you use in a year which you are now getting from your electric utility.  The best way to do that is to hook your PV system to the electric grid through a system called net metering.  You put energy into the grid when you have excess (summer afternoons) and you take energy from the grid when you are generating your own needs (night time or winter).  Net metering requires no batteries.  If the grid fails, you still have power as long as the sun shines.

If you want complete independence from the electric grid, you will need a larger number of panels and an on site storage system such as lead acid batteries.  This is a much more expensive solution.

Answer 3

It depends on your usage patterns compared to the output of the solar PV system.

You'll need to also be charging up batteries to ride through the nightime hours and days with cloud cover, rain, or other conditions that will prevent maximum output of the PV system.

If your loads cycle throughout the day, there might be enough power left over to charge the batteries.

If your home's peak load is 5 kW, I suspect that is the mid-day peak demand with the central AC running.  In the middle of the day 100% of your PV system's output will be used to power the AC.  You need to have some daylight hours where the PV output can also charge batteries.

I'd recommend a PV system with a slightly higer output.

You also have to factor in the inefficiencies of the inverter and slight losses associated with the battery storage.

Good luck.

Answer 4

You need to factor in time.  The amount of power your house uses in a month is measured in kilowatt hours or Kwh.  1 Kwh is the power necessary to supply 1 Kw for 1 hr.  Therefore, if you have a way of storing the energy generated from a solar cell (batteries), the power rating of the solar cell must be high enough that it produces more power in one day than you use in one day.

Lets say you use 100 Kwh per day and your solar cell gets 8 hours of good sunlight.  The solar cell must have a minimum rating of 100 Kwh/8 hrs. or 12.5 Kw to supply enough energy.

Answer 5

Well, it depends on what kind of load you are putting to your power supply. For example, if you are only using electronic devices like TVs radios or whatever, then it should be more than enough. Now if you are planning to use devices that run on ac like motors on a refrigerator or in a washing machine, then you should be careful because one thing is the average power you use and another thing is the apparent power you use. Generally motors tend to be very inductive which demands more power than the one you need. This is called reactive power. This is energy that you must borrow from somewhere and then your solar system won't be able to keep up with your demands. Specially at peak  hours. I would recommend you to measure your peak hours demand in apparent power and then you will know how big your solar system has to be. Think about what you will do at night as well. You need a storage system big enough to supply power for 12 hours at least because there are regions in the world that in winter they have really long nights. So it will depend too on where you are located.

I would say you find out the hours of sun light you get according to where in the world you are located so then you can make an approximate of what system to get.

Hope this helps.

Answer 6

Do you really mean only 5kw hours of electricity in a month? This is not very much. Electricity is measured by how many 1000-watts units are used by the hour. If you have a 1000 watt thing (lamp) on for one hour that uses one kilowatt hour.

Look at the meter on the side of your house. When a lot of appliances or lights are on it goes faster than otherwise.

One 1000 watt lamp on for one hour will use 1 kilowatt hour of electricity.

Ten 100 watt lamps on for one hour will use 1 kilowatt hour of electricity.

One 100 watt lamp on for ten hours will use 1 kilowatt hour of electricity.

One of those little 7 watt night light bulbs burning 24/7 for 30 days will use a little bit more than 5kw. It's not very much.