Solar Power For Homes

[forcebwithu]

@Zeb posted a good article about solar power use in Australia in the politics section. I think the article makes for a good opening post on the topic in the general area.

@thegrogmonster posted over on PA how he's receiving credits from the power company because his system generates more power than he uses.

After we finish painting the house, my next project is to look into installing solar. AI Bob does a good job of summarizing the costs, payback period and system size for our house in Pattaya (link).

I wish there was a govt program here that provided an incentive to install solar, or at the very least PEA would buy back the excess electric, but even without those incentives the payback for the solar install is estimated to be 6 to 7 years. With an expected life of 15 years for the panels, I'm surprised more are not installing solar.

Very low cost rooftop solar and batteries slashes domestic energy cost – Part 1: Australia

About 40% of Australian dwellings have rooftop PV, which is the highest rate in the world. Australia generates more solar electricity per person than any other country, from rooftop PV and solar farms.

A fully installed 10 kW system in Australia costs around $10,000 and lasts about 20 years. For many homeowners, the required rate of return on investing in rooftop PV is the house mortgage rate (6%), which equates to a tax-free real interest rate of about 2% after subtracting inflation. Real world annual output is approximately 1,300 kWh/kW per year.

These numbers translate to $0.05/kWh, which is far below retail tariffs.

Australian rooftop PV is much cheaper than in most countries. Reasons include the large scale of the industry, high skill levels, the absence of tariffs on Chinese solar panels, and Government regulations that are highly standardized and very smooth. Solar companies spend very little on advertising – rooftop PV is visible everywhere, which is its own advertisement.

The fraction of dwellings with rooftop PV is increasing by about 3% (absolute) per year. Many older systems are being upgraded. New rooftop PV systems have an average size of 11 kW. Many years ago, rooftop PV was kick-started by subsidies and attractive feed-in tariffs. Now it is driven by its compelling economic advantage.

In South Australia, the number of dwellings with rooftop PV has passed 50%, which means that half the population enjoys low electricity prices. Rooftop PV provides one quarter of annual electricity demand. It exceeds 100% of demand on sunny days, with the balance being exported eastwards. The grid remains very stable. South Australia is tracking towards 100% of its electricity from solar and wind on average in 2027. The wholesale spot market prices (corrected for inflation) is unchanged in the past decade.

Rooftop PV unlocks private money to produce vast amounts of clean electricity for houses, businesses and the grid. Government support is not required once the industry gets going. The grid remains highly stable even with high fractions of rooftop PV. Other countries can study Australian deployment methods and low-friction regulations.

An all-electric home has zero bill for natural gas or vehicle fuel. Energy storage is available in heat-pump hot water storage tanks (10-15 kWh), home batteries (10-40 kWh), and EV batteries (40-80 kWh). Simple timers can move operation of storage-charging, dishwashers, clothes washing & drying and house pre-heating & pre-cooling (via heat pumps) to daytime.

Rooftop solar combined with storage allows high energy resilience. If grid power fails, then the homeowner can carry on indefinitely with nearly normal house operation.

Uptake of EVs and heat pumps for water & space heating/cooling is starting to take off, strongly driven by the latest war in the Middle East.

Recently, the Australian Government implemented a very successful program to encourage the uptake of large (10-40 kWh) home batteries, usually coupled with new or expanded rooftop PV. Although the installed cost is quite high (around $350/kWh) and the payback period is long, many people enjoy the feeling of energy independence, and resilience if the grid goes down. Currently, about 3% (absolute) per year of Australian dwellings are installing home batteries.

Rooftop solar in Australia provides the cheapest, cleanest and most reliable domestic energy in history.

[fygjam]

https://pvoutput.org/

You don't have to register, just go to the various tabs.

 

[forcebwithu]

A C&P of the post I made over on PA about my quest for solar power.

I've done a bit more research on installing solar at our home using AI Bob (link). I have to say, using AI has been a great time saver for summarizing the info out there.

Turns out our house is ideally oriented for solar with the front of the house almost at a 180 degree azimuth, which I've learned is the ideal direction for Pattaya. That means the panels can be installed on the car port roof at the recommended 20 degree tilt. That will make the twice a year cleaning of the panels very easy from our second floor bedroom balcony.

Based on our usage a 9 panel (580W), 5.22 kW system should be adequate according to AI Bob, but will let a living breathing expert confirm that.

I'll also put in a battery system as we run the A/C in the master bedroom most nights.

@Mr.G [PA BM], I'll be interested to learn what panels, inverter and battery system you ultimately decide on. A more immediate question though, do you have a recommendation for a power consumption monitor? What I'd like to do is record our usage for the entire house for a couple of weeks to confirm my estimate of usage, and to factor in to my decision matrix whether a battery system is economically advisable.

Here's a cool sun tracker website that will let me figure out where the roof shadows will be during different times of the year. No doubt the professional installers do the same, but fun to do it on my own as well.

https://www.suncalc.org/#/12.9279,100.8995,15/2026.05.05/09:51/1/3

[KWA]

2 hours ago, forcebwithu said:

I wish there was a govt program here that provided an incentive to install solar, or at the very least PEA would buy back the excess electric . . . 

There is, or was, a buyback scheme and it was in the news again recently.  The more popular way to do it though is to keep your old dial meter and the system turns it back when you're exporting.  Just have to make sure the meter reader doesn't see it going backwards or you'll be changed to a smart meter without this capability.  Keep a small positive usage every month and you can do it forever.

https://www.bangkokpost.com/business/general/3253005/banks-tapped-for-solar-financing-push

 

[forcebwithu]

10 minutes ago, KWA said:

There is, or was, a buyback scheme and it was in the news again recently.  The more popular way to do it though is to keep your old dial meter and the system turns it back when you're exporting.  Just have to make sure the meter reader doesn't see it going backwards or you'll be changed to a smart meter without this capability.  Keep a small positive usage every month and you can do it forever.

https://www.bangkokpost.com/business/general/3253005/banks-tapped-for-solar-financing-push

It would be nice if they increase the buyback scheme's capacity limitation. But I wonder if it would be high enough for those lacking the connections with the higher ups to land a contract for the buyback.

That also begs another question, why do they have a limit on the buyback capacity? Probably the answer, as always, is certain groups benefit from a self-imposed limit.

[forcebwithu]

I asked AI Bob why the limit on the buyback program. Seems there are legitimate reasons behind the limitation.

The limitations placed on participation in Thailand's solar buyback scheme are driven by a mix of grid safety limitations, financial protection for state utilities, and strict bureaucratic policies. [1, 2]

While Thailand has an immense technical potential for solar power, authorities limit household participation to navigate several major challenges: [1, 2, 3, 4]

1. Grid Stability and Voltage Fluctuation

Most localized residential neighborhoods in Thailand are powered by small, older electricity transformers that were designed to send power in only one direction: from the utility to the home. [1]

• The Risk of Reverse Flow: When thousands of homes suddenly generate maximum solar power at midday, they dump large amounts of electricity back into the grid at the exact same time.
• Voltage Spikes: This massive reverse power flow can cause rapid voltage spikes, trip automated protection systems, or overheat and permanently damage neighborhood transformers. Local utilities protect infrastructure by capping how much solar can feed into any single transformer (usually ~15% of its total capacity). [1]

2. Safeguarding Utility Revenue and Existing Contracts

Thailand operates under a highly centralized energy framework heavily tied to long-term Power Purchase Agreements (PPAs) with massive private gas and coal power plants. [1]

• The "Stranded Cost" Problem: Under these long-term contracts, the government is contractually obligated to pay large power plants for energy capacity, whether the public uses it or not.
• Revenue Drop: If residential solar explodes without strict limits, grid electricity consumption plummets. The state utilities lose massive retail revenue but are still legally bound to pay for big centralized power generation, leading to heavy state financial deficits. [1]

3. High Cost of System Overhauls [1]

Allowing infinite solar buybacks would require a multi-billion-baht modernization of the national grid. Transforming the current infrastructure into a "Smart Grid"—complete with utility-scale battery storage networks, modern digital transformers, and dynamic net-metering systems—requires massive capital investments. The participation caps are used to slow down the adoption rate, giving state grid engineers adequate time to manually upgrade distribution hardware.

4. Bureaucratic Policy Bottlenecks

Historically, the strict 90 MW cap was written directly into the rigid national Power Development Plan (PDP) to stretch from 2021 to 2030. It was a political target rather than a physical limitation, creating a policy bottleneck that did not account for the rapid, massive drop in solar panel manufacturing costs. [1, 2]

To fix this policy bottleneck, the National Energy Policy Council shifted away from the hard 90 MW cap, implementing a rolling 500 MW system. This change aims to expand access safely while the grid infrastructure is systematically upgraded.

[forcebwithu]

One interesting tidbit from the above AI Bob response is the "10 kW household inverter capacity limit". That's for 3 phase, single phase the limit is 5 kW. AI Bob had more to say on the subject.

Yes, there is a strict 10 kW system capacity limit to participate in Thailand’s residential solar buyback scheme. [1]

To legally register for the 2.20 baht per unit grid feed-in tariff (FiT), your household system must be officially categorized under the "People's Solar" (Solar Phak Prachachon) program, which has an upper boundary of exactly 10 kW (or 10,000 Watts). [1, 2]

The electrical grid rules managed by the Metropolitan Electricity Authority (MEA) and the Provincial Electricity Authority (PEA) enforce these hardware limits based on your home's incoming electrical phase configuration:

Electrical Phase and Capacity Limits

Local utilities restrict how much power you can feed back into the grid to keep community infrastructure safe:

• Single-Phase Systems: Your inverter capacity is strictly limited to a maximum of 5 kW.
• Three-Phase Systems: Your inverter capacity is allowed up to a maximum of 10 kW. [1]

If your installer mounts a 12 kW or 15 kW inverter, you automatically cross over the residential classification line. This forces your property into a commercial scale system profile, subjecting you to rigorous commercial energy licensing, entirely different utility protocols, and exclusion from the 2.20 baht home tax-rebate scheme. [1, 2]

Strategic Ways Homeowners Handle the 10 kW Limit

Experienced solar developers and homeowners in Thailand navigate this rule using two main technical approaches:

• The Hybrid Battery Loophole: You can actually install more than 10 kW worth of physical solar panels on your roof, provided your grid-tied inverter output remains throttled to 10 kW. Homeowners pair excess panels with a hybrid battery storage system. The extra power produced at midday charges the local home battery bank directly instead of exporting to the street, completely bypassing the utility's grid feed-in limit.
• The "Zero Export" Route: If you want a massive system (e.g., a 15 kW system for a large villa with multiple air conditioning units) and do not care about the 2.20 baht payout, you can apply for a Self-Consumption with Zero Export permit instead. This requires a digital limiter clamp installed on your main electrical panel. It dynamically dials back your inverter's output so it never leaks a single watt back to the grid, liberating you from the 10 kW residential program cap.

[fforest]

Go talk to Tahitian Queen pattaya....Their entire roof is now, since when? Covered in some bad ass looking solar panels....I bet their electric bill has gotten a whole lot smaller....

 

 

Edited May 15 by fforest

[thegrogmonster]

I installed solar at our main house back in 2012 and locked in a good export rate for 17 years. I have not paid an electricity bill for this house since and I got the ROI back in 6 years.

In 2022 I installed solar on the holiday shack (now my fulltime place) but only receive the standard export rate. Some months I get a small refund but mainly have to pay a small bill each month.

Solar power generated each year at main house: 

Current power usage at main house:

[forcebwithu]

14 hours ago, fforest said:

Go talk to Tahitian Queen pattaya....Their entire roof is now, since when? Covered in some bad ass looking solar panels....I bet their electric bill has gotten a whole lot smaller....

 

 

Good to know. I'll have frind out who they used for the install and if they were good, use them for my install.

[Toy Boy]

I'd probably do it myself but a friend proudly showed me his setup and it had a large battery and inverter that he'd had them install in a store room. The trouble is that my house is chocker and, in the absence of a good buy-back scheme, you really need a decent battery. I've simply got no space to put them. 

[forcebwithu]

45 minutes ago, Toy Boy said:

I'd probably do it myself but a friend proudly showed me his setup and it had a large battery and inverter that he'd had them install in a store room. The trouble is that my house is chocker and, in the absence of a good buy-back scheme, you really need a decent battery. I've simply got no space to put them. 

I'm thinking of building a utility/battery closet on one of the outside walls. Mainly because I want a firewall between the battery packs and the interior of the house.

[fygjam]

2 hours ago, forcebwithu said:

I'm thinking of building a utility/battery closet on one of the outside walls. Mainly because I want a firewall between the battery packs and the interior of the house.

Looked at going solar many years ago. Some pertinent points at the time may still be relevant today.

Apparently it's a bit more than slapping a string of panels on the roof connected to an inverter then watching your power bills fade away to nothing.

Sunny Design was the bees knees of consumer systems design software. Google it.

Panel and inverter manufacturers are tier rated for a reason.

Panels are rated at environmental conditions which bear no resemblance to what may be found on a rooftop. Useful for comparison purposes though.

Panel output decreases with age. Design capacity for end of life not day one.

Inverter start voltage is higher than the lowest inverter run voltage. Design panel strings accordingly.

Panels have a negative temperature coefficient. Design panel strings accordingly.
For example, in Perth, a string has to cater for a zero degree frosty morning where the voltage of the string does not cross the low voltage/high voltage system threshold but would still start the inverter on a 45 degree summer day.

Inverters supporting multiple panel strings are more flexible.

Monocrystalline panels are king but polycrystalline are rapidly catching up.

A single shaded panel can take a string out. Some panels have a shade bypass built in.

DC circuit breakers are not the same as AC circuit breakers. If a DC breaker doesn't open fast enough or far enough you can get the arc welder effect rapidly followed by the whole fuking shitshow is on fire effect. Avoid cheap breakers.

 

[Butch]

12 hours ago, forcebwithu said:

I'm thinking of building a utility/battery closet on one of the outside walls. Mainly because I want a firewall between the battery packs and the interior of the house.

Easy to do, make it airtight and a fire suppression system is not too difficult to install. Our systems rely on 2 wires at low tension with a thin heat sensitive tag connecting them, when the temp hits a target, the tag breaks and the 2 wires trigger the fire suppression system and an alarm. (broken circuit and as a redundancy, when they break they both hit a pressure switch linked into the system).

Bear in mind depending upon the materials present, it can rapidly become a chemical fire, which is a problem.

 

 

 

This might be a bit of overkill though:

 

@Lantern is the Forum solar expert I think. Very knowledgeable guy on the subject.

I did read that solar panels are only 15% - 23% efficient which might have an impact. Are there any "next gen" ones worth waiting for?, the next question being if you fit now, and new panels with better efficiency come online, can they be retrofitted?.

Also, old car batteries are quoted as still being useful for some applications, but are deep cycle ones needed and worth the expense?.

Watching this with great interest as it's the direction we will soon be going in when we retire to the PI.

Edited May 16 by Butch

[forcebwithu]

7 hours ago, Butch said:

Easy to do, make it airtight and a fire suppression system is not too difficult to install. Our systems rely on 2 wires at low tension with a thin heat sensitive tag connecting them, when the temp hits a target, the tag breaks and the 2 wires trigger the fire suppression system and an alarm. (broken circuit and as a redundancy, when they break they both hit a pressure switch linked into the system).

Bear in mind depending upon the materials present, it can rapidly become a chemical fire, which is a problem.

This might be a bit of overkill though:

 

@Lantern is the Forum solar expert I think. Very knowledgeable guy on the subject.

I did read that solar panels are only 15% - 23% efficient which might have an impact. Are there any "next gen" ones worth waiting for?, the next question being if you fit now, and new panels with better efficiency come online, can they be retrofitted?.

Also, old car batteries are quoted as still being useful for some applications, but are deep cycle ones needed and worth the expense?.

Watching this with great interest as it's the direction we will soon be going in when we retire to the PI.

A foam fire suppression for a lithium iron phosphate battery fire won't work. To put that type of fire out requires use of a large amount of water to both cool the battery down and extinguish the fire.

 

[KWA]

If you have any intentions to sell back to the PEA, ensure your inverter is on their list of approved models as not all are.

List is on their website somewhere.

[monkey_omelette]

I've just had a quote for my gaff

 

20 X 645w Tier 1 panels

Hybrid inverter Solis 10kW

3 set Battery BYD 5 kWh

Total price installed 420,000 baht

ROI 5 years based on 4.6baht per kWh

Edited May 17 by monkey_omelette

[Butch]

8 hours ago, monkey_omelette said:

I've just had a quote for my gaff

 

20 X 645w Tier 1 panels

Hybrid inverter Solis 10kW

3 set Battery BYD 5 kWh

Total price installed 420,000 baht

ROI 5 years based on 4.6baht per kWh

Chunk of money but, if you intend to stay there then worth it, plus electricity probably won't come down in price over the 5 years.

[forcebwithu]

On 5/15/2026 at 7:32 PM, fforest said:

Go talk to Tahitian Queen pattaya....Their entire roof is now, since when? Covered in some bad ass looking solar panels....I bet their electric bill has gotten a whole lot smaller....

Waiting to hear back on the specs and who they used. Something of note on the install, the NW facing panels are not optimized for capturing most energy from the sun. 

[fforest]

1 hour ago, forcebwithu said:

Waiting to hear back on the specs and who they used. Something of note on the install, the NW facing panels are not optimized for capturing most energy from the sun. 

 

It's true that earlier in the day, these solar panels  position on the roof are not the greatest but in the afternoon and late afternoon on a sunny day the position is perfect for catching lots and lots of direct sun....

 

[forcebwithu]

Ahead of our move to solar power I wanted to get a handle on our electric consumption by time of day. That info will help me decide if battery storage for nighttime consumption is worth it. It'll also help with the correct sizing of the battery storage if I decide to go that route.

To measure consumption in real time I just installed the relatively inexpensive smart wifi energy monitor pictured below. That also required the install of the free Tuya mobile app for recording energy consumption.

The install was pretty easy, except I had a 50/50 chance of putting the amperage clamp on the correct feed to the house and guessed wrong on the first attempt. Thus the reverse energy red line in the graph below. The spike in the blue line that reflects consumption is from when I turned on the big A/C unit in the master bedroom. That about doubled the daytime house energy consumption, so now I have one data point on what I would need for nighttime consumption.

https://www.lazada.co.th/products/pdp-i5325520573-s22637058409.html

[forcebwithu]

I never did hear back from the company that installed TQ's solar system, but last week the owner, Daniel, of Kunini Solar came out to our homestead and did a site survey. Nice guy and a fellow hasher to boot.

Yesterday I received the quote of 362K baht for a Sigenergy 5kW Solar Hybrid Inverter with 9kWh Storage + 6kW of Solar PV. That's in the range of what I expected our home solar system to cost.

I replied with several follow up questions, which once answered I'll sign on the dotted line with the install to take place when the exterior house painting project has completed. Probably in about four weeks time.

The quote:

Follow up questions:
- I understand the optimal angle for my location is 20 degrees on a 180 degree azimuth. Is that needed for these panels?
- Below are screenshots of my daily electric consumption by hour for a monitor I installed on May 30th. Based on our consumption and allowing for a day of no sun, would additional battery storage be worth the cost?
- We're now in the weeks where the roof will experience the most shadowing. See below a few pics I took of the roof shadows in mid-morning and late afternoon. Will that affect the decision of where to place the panels?
- In your PV layout there is additional sunlit space on one of the easily accessible roofs that wasn't marked as used in the layout. The sunlit space is about 2.4m x 3m and is marked by the green rectangle in the PV layout below. That space might help with positioning two of the panels to a better location.
- What will be the PEA inspection fee that will be my responsibility?
- Would it be advisable to have PEA install a TOU meter at this time?
- The quote has ROI - Est Years, but the estimate is blank. What would you estimate for the ROI?

Edited Thursday at 02:07 AM by forcebwithu

[monkey_omelette]

1 hour ago, forcebwithu said:

I never did hear back from the company that installed TQ's solar system, but last week the owner, Daniel, of Kunini Solar came out to our homestead and did a site survey. Nice guy and a fellow hasher to boot.

Yesterday I received the quote of 362K baht for a Sigenergy 5kW Solar Hybrid Inverter with 9kWh Storage + 6kW of Solar PV. That's in the range of what I expected our home solar system to cost.

I replied with several follow up questions, which once answered I'll sign on the dotted line with the install to take place when the exterior house painting project has completed. Probably in about four weeks time.

The quote:

- We're now in the weeks where the roof will experience the most shadowing. See below a few pics I took of the roof shadows in mid-morning and late afternoon. Will that affect the decision of where to place the panels?
-

If you have shading maybe you should ask them to fit optimisers or micro inverters?

[forcebwithu]

40 minutes ago, monkey_omelette said:

If you have shading maybe you should ask them to fit optimisers or micro inverters?

I'll see what they have to say in response to my question on shading and will follow up with a question if micro inverters are worth the additional cost.

It's really only the weeks before and after summer solstice that the shading covers more of the roof than usual. There also is the option of using the top roof, but they're suboptimal given their orientation east and west.

[forcebwithu]

.

 

Edited Thursday at 04:55 AM by forcebwithu