Offsetting Your Aircon Bill with Grid-Tied Solar and Net Metering

Grid-tied solar with net metering offsets your aircon bill kWh for kWh, but not every kWh is worth the same: solar you use while it is being produced saves your full retail rate, while solar you export earns a credit at your electric company’s lower, generation-cost-based rate. So the best results come from an efficient inverter aircon, such as the TCL TAC-11CSD/P7 1HP split (650 W rated, CSPF 7.11 on its DOE label), that runs as much as possible while the sun is up, paired with a system sized to your daytime use.

This guide shows the maths step by step: how many kWh your aircon really uses, how much a grid-tied system produces, how exports are credited, and why the same panels save more on a daytime aircon than on a night-time one. For the cost and payback side, use our solar savings calculator and solar payback calculator with real quotes; we don’t quote equipment prices because they change daily.

How grid-tied solar “offsets” an aircon

A grid-tied (on-grid) system has three main parts: rooftop panels, a grid-tie inverter that turns the panels’ DC into 230 V AC, and a connection to your home’s main panel. There is usually no battery.

During the day, the inverter feeds solar power into your home’s wiring. Whatever is switched on at that moment, including your aircon, uses that solar first. If the panels produce more than the house is using, the surplus flows out to the grid through your meter. If the house needs more than the panels produce, the rest comes from the grid as usual.

Three things follow from this:

1. Solar never “runs” the aircon on its own. It shares the load with the grid, moment by moment. On a cloudy afternoon, most of your aircon’s power may still come from the grid.
2. At night, solar does nothing. A bedroom aircon running from 10 pm to 6 am is powered entirely by the grid, unless you have a battery.
3. In a brownout, the system switches off. A grid-tied inverter must disconnect when the grid goes down so it doesn’t feed power into lines that line workers think are dead. Meralco’s commissioning tests check that the system disconnects within 2 seconds of an outage and reconnects only 10 minutes after power returns. If you want your aircon or other loads to keep running in a brownout, you need a hybrid system with a battery. Our comparison of on-grid, hybrid and off-grid solar explains the trade-offs.

Step 1: Work out your aircon’s kWh

Solar is measured in kWh (energy over time), so start with your aircon’s monthly kWh, not its watts.

The basic formula is:

Monthly kWh = rated watts × hours per day × days ÷ 1,000

That gives an upper figure, because an inverter aircon slows its compressor once the room is cool and often runs below its rated power. How far below varies with the room, the weather, the thermostat setting and how well the room is sealed.

The DOE’s energy label gives a standard estimate. On older labels, the “Monthly Energy Consumption” figure is calculated as power input (kW) × 9 hours × 30 days × a factor of 0.5 for inverter (variable-speed) units or 0.8 for fixed-speed units. Newer labels print lower monthly figures on a different basis, so only compare label kWh between labels of the same issuance year. In the table below we apply the older-label formula to every model ourselves, so the figures are directly comparable.

Rated input and CSPF are from each model’s DOE energy label, except the TCL TAC-09CSD/FBI, whose figures come from TCL’s own spec sheet. CSPF (Cooling Seasonal Performance Factor) is the label’s efficiency rating: the higher it is, the more cooling you get per kWh.

The label formula assumes 9 hours a day. If you run your aircon 8 hours a night, or 12 hours on hot weekends, scale it: for the TCL P7 1HP, 8 hours a day on the same basis is 0.65 × 8 × 30 × 0.5 = 78 kWh a month. If you want to see your own estimate, the aircon electricity cost calculator does this for you, and our guide to aircon electricity consumption explains the variables.

Fix the aircon before you size the solar

Every kWh your aircon doesn’t use is a kWh you don’t need panels for. Going from the 850 W TCL UB2 window unit to the 650 W TCL P7 split saves 27 kWh a month on the label basis (114.75 − 87.75). At our example output of 96 kWh per kW of panels (Step 2), that is close to 0.3 kW of panels you don’t need. A fixed-speed unit usually adds much more. Our explainer on inverter vs non-inverter aircons shows why, and our guide to solar aircon costs and payback works through an upgrade example.

Step 2: Estimate what the panels will produce

Solar output depends on your roof, shading, tilt, temperature and weather, so any single figure is an estimate. A common way to make one is:

Daily kWh = system size (kW) × peak sun hours × system efficiency

On these assumptions, 1 kW of panels produces about as much in a month as the TCL P7 1HP uses on the label basis (96 vs 87.75 kWh). For the 850 W TCL UB2 window unit, you’d need about 1.2 kW (114.75 ÷ 96). For the 1.5HP TCL P7, about 1.4 kW (135 ÷ 96).

Panel counts depend on each panel’s wattage, so divide the system size by the panel rating your installer quotes. If you want to plan the whole house, not just the aircon, see how many solar panels a Philippine home needs and the solar system size calculator.

Step 3: Understand how exports are credited

This is the part most people get wrong. Net metering is a program under which customers of a distribution utility can install a renewable energy system of up to 100 kW and export the electricity they don’t use. The DOE describes the export credit as “peso credits … equivalent to the DU’s blended generation cost, excluding other generation adjustments.”

In plain terms:

• Imports are billed in full. Every kWh you take from the grid is charged at your usual rate, including generation, transmission, distribution, taxes and other charges.
• Exports are credited at a lower rate. The credit is based on the generation part of the bill only, not the whole retail rate. It differs by utility and changes every month.
• Credits reduce your bill but are not cash. Meralco says unused credits carry over to later bills but can’t be converted to cash.
• Without net metering, exports can cost you. Meralco warns that without net metering, the excess electricity your solar produces may be recorded as imported energy. If you don’t want to export at all, Meralco offers Zero Export instead.

Our full explainer on net metering in the Philippines covers the rules, meters and paperwork, and net metering by electric company lists each electric company’s published steps and fees.

Step 4: The worked example — night aircon vs daytime aircon

Here is the same system, and the same aircon, used two different ways.

System: 1 kW of panels, about 96 kWh a month on our example assumptions.

Scenario A: bedroom aircon, used only at night

• The aircon’s 87.75 kWh are all imported at night: 87.75 × ₱12 = ₱1,053.
• The panels’ 96 kWh are produced during the day, when the aircon is off, and exported: 96 × ₱6 = ₱576 credit.
• Net cost of the aircon: ₱1,053 − ₱576 = ₱477 a month.

Scenario B: the same aircon, used during the day

Think of a home office, a sari-sari store, or a family that stays home on hot afternoons. Solar output and aircon use won’t match perfectly, so assume (as an example) that solar covers 80% of the aircon’s kWh directly.

• Aircon kWh covered directly by solar: 87.75 × 0.8 = 70.2 kWh. That’s 70.2 × ₱12 = ₱842.40 not bought from the grid.
• Remaining aircon kWh from the grid: 17.55 × ₱12 = ₱210.60.
• Remaining solar exported: 96 − 70.2 = 25.8 kWh × ₱6 = ₱154.80 credit.
• Net cost of the aircon: ₱210.60 − ₱154.80 = ₱55.80 a month.

Same panels, same aircon, same sunshine. In Scenario B, the solar is worth ₱997.20 a month (₱842.40 + ₱154.80). In Scenario A, it is worth ₱576. The difference comes entirely from when the aircon runs.

What this means in practice

• Shift cooling into sunny hours where you can. Pre-cool a bedroom in the late afternoon while the panels are still producing, then let the inverter aircon coast at a lower setting after sunset.
• Don’t oversize for export. A system much larger than your daytime use mostly earns export credits, which are worth less per kWh. That can stretch payback.
• Count the rest of the house. In a real home, the refrigerator, fans, Wi-Fi and other loads also use daytime solar. That’s good: every kWh you use yourself is worth the full rate. Your installer should look at your whole daytime load, not just the aircon.

Step 5: Put real costs into the calculators

We don’t state equipment or installation prices: they change daily and vary by roof, brand and installer. Instead:

1. Get at least two written quotes from licensed installers. Our solar installers directory and compare solar quotes page can help.
2. Enter the quote, your monthly kWh and your rate into the solar savings calculator to estimate monthly savings, including the split between self-used and exported solar.
3. Use the solar payback calculator to see how many years it takes to recover the cost.
4. Check your electric company’s current rate on our electricity rates page. Rates move every month, and payback is sensitive to them.

If you’d like to see how the maths changes with different aircons, rates and setups, our guide to solar aircon costs and payback goes deeper.

Step 6: What a licensed installer does

A grid-tied rooftop system connects to your home’s wiring and the electric company’s grid, so it isn’t a DIY project. Under the Philippine Electrical Engineering Law (RA 7920, Section 34), electrical plans must be prepared or supervised, signed and sealed by a professional electrical engineer (PEE), a construction or electrical permit must be secured first, and the work must follow the Philippine Electrical Code under a licensed professional’s supervision.

In practice, a good installer will:

• Check your load and roof. Daytime use, roof direction, shading and structure.
• Check grid capacity. Meralco publishes indicative hosting capacities for its distribution transformers and runs a Distribution Impact Study on each application. A system larger than your local transformer can host may need upgrades.
• Handle permits. The LGU electrical permit and, after installation, the Certificate of Final Electrical Inspection (CFEI), which Meralco lists among its net-metering requirements.
• File the net-metering application with you, since the account holder is the applicant. The electric company then inspects, installs a bi-directional meter and commissions the system.
• Set up monitoring so you can see how much solar the house uses directly and how much it exports. That tells you whether shifting aircon use is working.

Don’t export power until the bi-directional meter is installed and the electric company has approved you. See our residential solar installation guide for the full journey from quote to switch-on.

Common mistakes when offsetting an aircon with solar

• Sizing from watts instead of kWh. A 1HP aircon “being 850 W” doesn’t tell you how many panels you need. Its monthly kWh does.
• Trusting listing wattages. Some listings print a maximum figure as if it were the rated input. For example, the TCL TAC-09CWI/UB2 Lazada listing says “1450 watts”, while its DOE label says 850 W (1,450 W is the top of its 200–1,450 W range). Use the label figure for energy maths.
• Assuming credits equal savings. A ₱1 export credit is not worth the same as ₱1 of avoided import. Use both rates in your estimate.
• Expecting backup. Grid-tied without a battery means no aircon (or anything else) from solar during a brownout.
• Skipping the aircon upgrade. An old fixed-speed unit can use far more kWh than a 5-star inverter unit, which means more panels for the same comfort.

What to buy: checklist

1. An efficient inverter aircon (do this first). Verified picks from DOE labels and manufacturer spec sheets:

• TCL TAC-11CSD/P7 (1HP split, 650 W, CSPF 7.11, 5 stars): Shopee (TCL Official Store) · Lazada (TCL). The same listings also offer the TAC-14CSD/P7 1.5HP (1,000 W, CSPF 6.74).
• TCL TAC-09CSD/FBI (1HP split, 660 W, CSPF 6.28 per TCL’s spec sheet): Shopee (TCL Official Store) · Lazada (TCL)
• Kolin KA-100GQAIINV32 (1HP window, 740 W, CSPF 5.60, 4 stars on its newer label): Lazada (Kolin)
• TCL TAC-09CWI/UB2 (1HP window, 850 W, CSPF 5.12, 5 stars): Shopee (TCL Official Store) · Lazada (TCL)
• Samsung AR60H13D1FWNTC (1.5HP split, 1,030 W, CSPF 5.70, 5 stars): Shopee (Samsung AI Home)

Have the aircon installed by the brand’s authorised installer or a licensed technician on a properly rated circuit.

2. A grid-tied system from a licensed installer. Ask for:

• A written production estimate in kWh per month for your roof
• The panel and inverter datasheets
• The PEE-signed plan, LGU permit and CFEI
• Help with your electric company’s net-metering application (steps by utility)
• Monitoring that shows self-consumption and exports separately

3. Your numbers. Your monthly kWh from your bill, your rate from electricity rates, and your quotes in the solar savings and solar payback calculators.

Bottom line

Grid-tied solar with net metering can offset most of an efficient aircon’s kWh, but how much money that saves depends on timing. Each kWh you use as it’s produced saves your full rate. Each kWh you export earns a lower, generation-based credit. Start with an efficient inverter aircon such as the TCL TAC-11CSD/P7 or Kolin KA-100GQAIINV32, size the system to your daytime use with a licensed installer, move cooling into sunny hours where you can, and run your own quotes through the calculators before you sign.