How much 500W solar panels (Ongrid) I need for reduce my electric bill 40-50%?

[snowgard]

My electric bill shows we use between 550-800 Kwh per month. With a Ongrid solar system how much pannels of 500W I need to reduce it around 40-50%?

[JBChiangRai]

Do you have a spinning disc meter? If so 3 to 6Kw will save you 40 to 80%
 

If you have a digital meter it’s a bit more complicated

[connda]

Given the government's promise to raise electric bills we're thinking about this too.  I just want to power our A/C units which are more likely the primary electricity draws on our bills. 

My wife balked when I first mentioned it, but I thinks she's warming up to the idea. 

[Liverpool Lou]

16 minutes ago, connda said:

Given the government's promise to raise electric bills

Really?   Where has that been stated?

[UWEB]

45 minutes ago, snowgard said:

My electric bill shows we use between 550-800 Kwh per month. With a Ongrid solar system how much pannels of 500W I need to reduce it around 40-50%?

You need a 8-10 kw System if you calculate for a period of on year, Summertime it will produce more but in raining Season less.

[snowgard]

1 hour ago, JBChiangRai said:

Do you have a spinning disc meter? If so 3 to 6Kw will save you 40 to 80%
 

If you have a digital meter it’s a bit more complicated

I have a spinning disc meter. But 80% is unrealistic without batteries because in the nighttime 3 aircons are running. 

[motdaeng]

7 hours ago, snowgard said:

I have a spinning disc meter. But 80% is unrealistic without batteries because in the nighttime 3 aircons are running. 

 

you need to check your usage from 8:00 am to 6:00 pm. only in this timeframe can you save some money by installing solar without a battery.

[Ben Zioner]

27 minutes ago, motdaeng said:

 

you need to check your usage from 8:00 am to 6:00 pm. only in this timeframe can you save some money by installing solar without a battery.

But based on my [rough] calculations stored energy will cost you more than the PEA supply. I'd used solar keep the house cool during hot hours, bake bread, and hot water. 8 to 10 KW solar gives probably the best savings for the average house.

 

Forget about selling to PEA at 2.2 Baht a KWh.

[steve187]

1 hour ago, motdaeng said:

 

you need to check your usage from 8:00 am to 6:00 pm. only in this timeframe can you save some money by installing solar without a battery.

yes, take a reading at 8am and again at 5pm for a week or so and see when most of your power is being used, that would indicate the amount of panels and battery size that would be required, my 5 kwh/11.5kwh battery system has produced on average 14kwh per day over the 210 days since install, that includes rainy/cloudy days and bright sunshine days.

Edited July 24 by steve187

[Ben Zioner]

1 hour ago, Ben Zioner said:

But based on my [rough] calculations stored energy will cost you more than the PEA supply. I'd used solar keep the house cool during hot hours, bake bread, and hot water. 8 to 10 KW solar gives probably the best savings for the average house.

 

Forget about selling to PEA at 2.2 Baht a KWh.

BTW I am considering something like this. What slows me is that I'd need to cover two separate roofs one south facing the other west. The second one being quite elevated.

 

Also when it comes to backup power, a 10 KW Genset will come cheaper than any battery. Therefore IMHO 10KW On grid + Genset, if really needed, is the way to go these days. But in 3 years time it could all change. 

 

And than I am not in a remote area, where for new houses, the cost of a PEA connection comes into the equation 

Edited July 25 by Ben Zioner

[JBChiangRai]

9 hours ago, snowgard said:

I have a spinning disc meter. But 80% is unrealistic without batteries because in the nighttime 3 aircons are running. 

 

With a spinning disc meter it is possible to use PEA as a battery and spin the disc backwards during the day and forward at night.  PEA don't like it, it is not illegal but it is against their rules and if they catch you they will fit a digital meter which prevents this.

 

PEA are slowly changing all meters to digital, so it's a lottery how long you can do this.  Generally, payback is about 3 years.

 

In Chiang Rai, myself and 3 other friends all do this.  It does take some management, I have to turn off my solar system on meter reading day, and when my meter is changed to digital, I will have to set my system to "no-export".

 

This method depends entirely on your appetite for risk.

[snowgard]

3 hours ago, Ben Zioner said:

BTW I am considering something like this. What slows me is that I'd need to cover two separate roofs one south facing the other west. The second one being quite elevated.

 

Also when it comes to backup power, a 10 KW Genset will come cheaper than any battery. Therefore IMHO 10KW On grid + Genset, if really needed, is the way to go these days. But in 3 years time it could all change. 

 

And than I am not in a remote area, where for new houses, the cost of a PEA connection comes into the equation 

Hahaha,,, 379.000 THB are expensive!!! With my actual consumption and electric price the ROI will be after 14+ years. 

Not something what I want!!! 🙃

[motdaeng]

3 hours ago, JBChiangRai said:

PEA don't like it, it is not illegal but it is against their rules and if they catch you they will fit a digital meter which prevents this.

 

i strongly disagree with you on this (you say it's not illegal, so it must be legal?).

if you get catched, the consequences could be quite unpleasant, depending on the boss of the pea!

[degrub]

3 hours ago, JBChiangRai said:

 

With a spinning disc meter it is possible to use PEA as a battery and spin the disc backwards during the day and forward at night.  PEA don't like it, it is not illegal but it is against their rules and if they catch you they will fit a digital meter which prevents this.

 

PEA are slowly changing all meters to digital, so it's a lottery how long you can do this.  Generally, payback is about 3 years.

 

In Chiang Rai, myself and 3 other friends all do this.  It does take some management, I have to turn off my solar system on meter reading day, and when my meter is changed to digital, I will have to set my system to "no-export".

 

This method depends entirely on your appetite for risk.

The rule is there to protect their lineman from a nasty shock or electrocution when they are working on a supposed to be dead, disconnected distribution line.  The few baht you save is hardly worth a life.

[patman30]

13 hours ago, snowgard said:

I have a spinning disc meter. But 80% is unrealistic without batteries because in the nighttime 3 aircons are running. 

i am off grid but same applies
what you can do is run the aircons full blast while the sun is out
and cool the house down as much as possible
this will save you energy once the sun has gone down
the early evening is when most power is used cooling the house down (cooling upstairs down for me)
night time is not so bad once the house is cool
you can also save energy by using aircons and a fan (always check watts fan will use when buying, it varies a lot)
when we have excess sun (rarity this year TBH) i just turn all aircons on
just to get the house as cool as possible so i can save on battery during the night

if you plan for on grid without battery
you can only save what you use during the day
regardless what meter you currently have, you will soon have a digital meter, just a matter of when.
without knowing anything about your use
i would suggest you do plan to add more later if needed
but simply start with a decent 1 x 5KW inverter and panels and see how you go
if you need more juice during daytimes, then add another inverter and more panels
 

[patman30]

4 hours ago, Ben Zioner said:

BTW I am considering something like this.

that looks a rip off

35k for Growatt hybrid 5KW inverter (can get ok inverters from about 15K) = 70k
20 x 550w panels cost = 60k
subtotal 130K
leaves quite a bit of change for labour, fittings and breakers etc.

[JBChiangRai]

1 hour ago, motdaeng said:

 

i strongly disagree with you on this (you say it's not illegal, so it must be legal?).

if you get catched, the consequences could be quite unpleasant, depending on the boss of the pea!

 

There are rules and there are laws.  There is no law saying you must not give electricity to PEA and take it back later. It is not theft.

 

It is against their rules, they are most likely to change your meter, in theory, they could sue you for loss of income, but not theft.

 

1 hour ago, degrub said:

The rule is there to protect their lineman from a nasty shock or electrocution when they are working on a supposed to be dead, disconnected distribution line.  The few baht you save is hardly worth a life.

 

What you are talking about is impossible.  All Grid-Tied inverters have anti-islanding, meaning they cannot operate when the PEA line goes down.  Even a grid-tied inverter set to no export will operate exactly the same way, the moment the PEA line goes down they shut down.