Rooftop solar

Recent days have been oppressively humid and warm and as expected, the start of our “brownout season.” High cost of power and an unreliable power sector had long been a pain. Potential investors also cite these as a deal breaker for them.

 More and more people want to declare independence from the power grid. Fortunately, this is possible today and banks are making it within reach. Indeed, a rooftop solar installation for a typical middle-class home is now cheaper than a car.

I remember the early days in the 80s when we were testing all sorts of what we called non-conventional energy systems. We started testing solar power at the Non-conventional Energy Center on Commonwealth Avenue.

This was before silicon solar panels became popular and relatively cheap. The system used the sun to heat up water in rooftop panels and made it flow into tubes and machines in a room below. The equipment to cool the conference room was as large as the conference room. And a PhD in engineering was running it.

Now, nothing could be simpler and cheaper. Thanks to advances in technology and with China overproducing solar panels, even middle-class homes can decouple from the grid.

When my son was still living in California, he had some solar panels on his rooftop. During the day, he sold the power produced to the grid. He bought power from the grid at night. At midnight when the price of power from the grid was lowest, his VW EV was programmed to charge and his fully charged car was ready in the morning.

 But so many climate-change conscious Californians started doing the same thing and the local utility wasn’t happy. Losing business was one thing. But having thousands of megawatts from rooftops of ordinary homes disrupting the stability of the grid is a serious problem.

The fast increase in the number of homes with rooftop solar panels was causing severe imbalances between supply and demand, reversing power flow in systems designed for one-way distribution, and creating rapid, erratic fluctuations in voltage. The grid faced challenges in maintaining its standard operating frequency and voltage limits, often leading to equipment damage or blackouts.

When intermittent solar energy enters the grid, traditional base load plants (such as coal, natural gas) face severe operational stress. Because these plants were designed to run continuously at a constant output, the rapid fluctuation of solar power was damaging them.

Constantly heating up and cooling down large metal components causes rapid wear and tear. Component stress leads to more frequent equipment failures and unscheduled maintenance outages. The overall operational lifespan of a power plant’s multi-million-dollar boilers and turbines is severely reduced.

The laws of physics cannot be repealed. Fundamental thermodynamic, material science and mechanical principles must be observed.

The vast majority of residential rooftop solar installations are standalone, grid-tied systems without battery backups. And that’s the problem. So, US utilities started to discourage standalone solar with no battery back-up.

It will presumably be less of an operational problem for utilities if households with rooftop solar completely cut themselves from the grid. But these households must then invest in a storage battery for 24/7 power, significantly increasing the payback time of a rooftop installation.

There is another policy problem that energy officials must deal with. What happens when utilities – which are in the business of selling electricity – continue to lose business?

The more kilowatt-hours generated by rooftop solar panels, the fewer kilowatt-hours sold by utilities. With fewer kilowatt-hours sold, utilities can’t justify investments in new power sta-tions, transformers and other types of capital investments required to make the grid reliable.

Getting a zero billing from Meralco, through net metering, makes one feel victorious. But the cost of building and maintaining the grid, to which the zero-billing household is still connected as backup, would then fall on those who cannot afford to buy a rooftop solar installation. This has the unintended consequence of making rooftop solar an anti-poor alternative.

Still, there is increasing interest in rooftop solar. BPI has reported a rapid growth in solar financing. It reported during its annual stockholders meeting that their solar financing portfolio grew by 89 percent in 2025, bringing outstanding balances for solar loans to P100 million.

With installations costing as little as P500,000, BPI forecasts that residential solar installations will grow by 32 percent in the next five years.

Commercial mega-malls like the SM Supermalls network are achieving massive financial savings from their rooftop solar installations, driven by the country’s high commercial electricity rates (which often exceed) 10 per kilowatt-hour and rising).

 SM has deployed over 200,000 solar panels across 59 mall properties, spanning 65 hectares of rooftop space. It allows SM to displace hundreds of gigawatt-hours of daytime grid power. At commercial rates, this network-wide portfolio saves SM an estimated P600 million to P1 billion annually in avoided utility bills.

Commercial installations of this scale benefit from a quick payback period of four to six years. Because commercial solar panels carry an operational lifespan of 25+ years, it guarantees nearly two decades of free daytime electricity after breaking even.

SM does not have battery backups. They have a grid tie-up, exporting any excess generation into the grid. They depend on standby generators during power failures.

There are benefits for cutting yourself completely from the grid. You don’t have to pay for government’s failures (universal charges) and utility line losses.

Rural electrification, solar power incentives (FIT-All and GEA-ALL) as well as subsidies for the poor and senior citizens are government programs which should be provided for in the national budget. Otherwise, these are effectively additional taxation imposed on grid electricity users.

Worse, VAT is added to charges for system loss and subsidies to poor and senior citizens.

Solar’s time has come. But the government must carefully manage the transition from a grid designed for conventional energy.

Boo Chanco’s email address is [email protected]. Follow him on X @boochanco