Solar systems for needs of whole house

[scorecard]

(As suggested I am re-posting this topic to the electrical forum - hope that's ok.)

I've noticed some articles saying it's getting easier and cheaper to install a home solar system to cover all the electricity needs of a typical family house.

My knowledge of this subject is zero and i'm guessing lots of folks would be interested to get some up to date information on this.

Can the electrical / solar experts on this subject please share some facts. Not interested in wild unfounded comments, just facts and real opinions from the experts.

Thanks.

Edited March 25, 2016 by scorecard

[Crossy]

There are a couple of threads by GinBoy2 discussing his installation and the paperwork needed by PEA to make it all legal. Worth a read.

Ok. First question, do you have available mains power? Is it reliable?

If mains is available and reasonably reliable then a grid-tied or on-grid system (no batteries) will give fastest return on investment (about 7-8 years) but does not maintain supply when the grid is off.

If no mains available at all then you'll need a pure off-grid system, lots of (expensive) batteries to provide power when the sun is asleep. ROI much, much longer (possibly never if you factor in the cost of replacing the batteries).

If you have mains, but it's unreliable then a hybrid system may be the best idea. As a cross between on-grid and off-grid it provides limited power when the grid is off but the battery costs are a lot lower than a pure off-grid system.

As to system size:-

For a quick and dirty guesstimate, take your monthly usage in kWh (units), divide by 30 to get your daily consumption then by 24 to get hourly consumption. Multiply that by 4.8 (assuming 5 hours of generation per day) and you get the (very approximate) size of a system to provide most of your daily usage.

Note that this simple estimate really only works for a grid-tie system where you have the grid to make up any shortfall. If you want to be fully off-grid then you have to factor in battery capacity to cover for dull days etc.

For example:- We use about 1100 units a month (bill is about 4,000 Baht), giving a daily usage of 36.6 units = hourly usage of 1.5 units. So we would need a system capable of supplying 1.5 * 4.8 = 7.3 kW

If going grid-tie, any size system will reduce your power bill, you don't have to go the whole hog at once, you can add more panels and inverters (and further reduce your bill) as an when the need (or funds) allow.

[scorecard]

Crossy thanks very much for your informative summary.

To be honest I'm aiming to reduce the electricity bill, currently around 2,500 - 3,500Baht a month depending on the season (in Chiang Mai). It's actually my son's house and I'm always interested to look for anything that will over time reduce his utility etc., bills.

The two main items are air conditioners (2 to 3 units on all night except for about 6 weeks per year) and all electric cooking and oven. Plus 3 bathroom water heaters and many lights, 3 TVs, 2 fridges etc.

Going full solar (probably with connection to the outside grid but rarely ever used) is obviously attractive in terms of monthly electric bill costs but as you and others mention it's quite an investment, especially for the storage batteries.

I also wonder if right now if there enough professional knowledge available in Thai engineers / technicians on this subject, to design a ystem and install it, and quickly and accurately diagnose faults and quickly complete repairs.

For now I guess the best approach is a small system aimed at just cutting the current bill, perhaps by 40/ 50% as a goal but not needing too much investment. But perhaps that's unrealistic because the air conditioners are mostly used at night time so any system installed would need batteries.

Ultimately i'm wondering whether longer-term full solar systems will get lots more development (perhaps this might come from push to stop power station pollution etc.) and costs will ultimately come down (perhaps also come down because of a bigger market for the equipment) and become widely used by many private / household users. But of course no real answers to this scenario right now.

[Crossy]

SC a grid-tie would do the trick. During the day your meter will spin backwards as you are exporting power to the grid, it will go forwards again at night when your aircon is running.

It's called 'net-metering' and it is the reason grid-tie is so popular. You effectively use the grid as your battery.

BUT, the fact that the meter goes backwards can set off the alarm bells with the meter reader, this is why it is important to get the proper paperwork in place from your local electricity authority.

Have a look at the AmornSolar website http://www.amornsolar.com/index.php for some idea of costs, remember the costs do not include installation and all the ancillary bit-n-bobs (like panel mounting kits).

http://www.amornsolar.com/images/pdf/ongrid/ongrid_system.pdf

I don't know if this installation promotion is still valid, but you can see the installation costs http://www.amornsolar.com/promotion-install.php

[scorecard]

SC a grid-tie would do the trick. During the day your meter will spin backwards as you are exporting power to the grid, it will go forwards again at night when your aircon is running.

It's called 'net-metering' and it is the reason grid-tie is so popular. You effectively use the grid as your battery.

BUT, the fact that the meter goes backwards can set off the alarm bells with the meter reader, this is why it is important to get the proper paperwork in place from your local electricity authority.

Have a look at the AmornSolar website http://www.amornsolar.com/index.php for some idea of costs, remember the costs do not include installation and all the ancillary bit-n-bobs (like panel mounting kits).

http://www.amornsolar.com/images/pdf/ongrid/ongrid_system.pdf

I don't know if this installation promotion is still valid, but you can see the installation costs http://www.amornsolar.com/promotion-install.php

Wow interesting, I'll pass all of this over to my Thai adult son, he can do the talking in Thai to Amorn etc., and then explain it all back to me in English.

Thanks again, much appreciated.