Common myths about solar energy in Colombia

Panels produce less under cloud, but they keep generating. The reason is that they also make use of diffuse radiation, the light scattered by the atmosphere rather than arriving in a straight line from the sun. An overcast day is not a day of zero output: it is a day of reduced output.

Colombia also has an advantage that is usually summarised badly. What matters is not maximum irradiation — there are places with more — but its stability: because of the proximity to the equator, day length barely varies and the sun stays high all year. That makes annual generation more predictable than at latitudes with marked seasons.

What does vary a great deal is irradiation between regions. La Guajira and much of the Caribbean coast are clearly above the national average; areas of heavy cloud cover, below. That is why a production estimate that does not say which region it refers to means nothing.

The nuance that matters when buying: ask which irradiation value the installer used to estimate your output. If they do not state it, the number is not verifiable.

False for the vast majority of grid-connected homes, and probably the most expensive myth of all, because storage is the line item that most alters a residential budget.

The net metering scheme, now regulated by CREG Resolution 174 of 2021, lets you export surplus to the grid and take it back when the system is not producing. In practice the grid works as a virtual backup, with no equipment cost and no degradation.

Batteries solve a different problem: having power when the grid goes down. That is their legitimate use case, and there are situations where it is fully justified — areas with frequent outages, properties with no grid connection, loads that cannot tolerate interruption. But they are justified by the cost of being without power, not by extra savings.

The right way to assess them is to list which specific loads have to keep running and for how long, not to size backup for the whole house. Almost always the critical set is a small fraction of the total.

A photovoltaic solar system has no moving parts. That sets it apart from almost any other generation technology and explains why its maintenance is among the lowest there is.

In practice it comes down to two things: cleaning the modules as often as the environment demands, and a periodic inspection of connections, structure and the state of the inverter. In an area with regular rain, the rain itself does much of the work; near an unpaved road, an agricultural area or an industry that generates dust, cleaning has to be considerably more frequent.

What is worth dismantling is the opposite myth, which is equally false: that a solar system needs no attention at all. The component to keep an eye on is the inverter, because it has the shortest service life and can fail without anyone noticing for months if there is no monitoring.

A system that has stopped does not announce it. It still looks the same from the ground while your bill quietly returns to what it was before.

This is perhaps the most expensive myth, because it is the one the least serious proposals use as a selling point.

The saving depends on at least four variables: how much you consume, what tariff you pay — which varies by stratum and by whether you are a residential, commercial or industrial user — the irradiation in your area, and what time of day you consume. Changing any of them moves the result significantly.

The fourth is the one most often overlooked. The energy you self-consume saves you the full tariff; what you export is offset according to what the regulation sets, at a value that need not match it. Two identical homes with the same system save different amounts if one is out all day and the other is not.

So any promise of a fixed percentage without seeing your bill is marketing, not a calculation. An honest estimate is presented as a range, with its assumptions stated: the irradiation used, the performance ratio, the starting tariff and what fraction of generation is assumed to be self-consumed.

It does not, and it is worth knowing that before signing rather than discovering it on the first bill after installation.

An electricity bill has more components than the energy consumed. The fixed retail charge is paid for being connected, regardless of how much energy you draw from the grid, and a solar system does not eliminate it. As long as you stay connected — which is what you want, because the grid is your backup — that component remains.

A well-sized system substantially reduces the variable part of the bill. That is a great deal, and it is usually enough to justify the investment. But it is different from taking it to zero.

There is a practical consequence: be wary of a proposal that uses 'zero bill' as an argument. Either it does not know the tariff structure, or it knows it and prefers not to mention it.

It is intuitive and it is false. Photovoltaic modules convert light, not heat, and their performance falls as cell temperature rises.

Every module has a temperature coefficient that quantifies that loss: for every degree above the reference temperature, the power delivered drops by a small but cumulative percentage. On a metal roof under the Caribbean sun, cell temperature can be far above air temperature.

This does not mean the coast is a bad place to install: the higher irradiation more than compensates for the thermal loss. It means the design has to take it into account, leaving ventilation under the modules and not calculating output as though they were working at laboratory temperature.

If an output estimate for a hot area does not mention the temperature correction, it is probably overestimating.

Modules do not 'break' suddenly: they degrade slowly and predictably. Each year they produce a little less than the previous one, by a low, known percentage that the manufacturer declares.

That is why performance warranties are expressed over twenty-five years, committing to a minimum percentage of the initial capacity at the end of that period. A twenty-year-old module is still producing, just somewhat less than when it was new.

The component that does have a clearly shorter service life is the inverter, and there a replacement should be allowed for within the project horizon. A twenty-five-year financial model that does not include it is incomplete.

The other point that gets ignored is the installation warranty, which is a third thing distinct from the module's and the inverter's. When a proposal talks about '25 years of warranty' without breaking it down, it almost always means the module only.