Why does your neighbour pay less for electricity than you?

It is a scene repeated in any neighbours' group chat: someone shows their bill, someone else shows theirs, and the figures look nothing alike even though the houses do. From there comes the same hasty conclusion: one of the two is being overcharged.

Sometimes that is true. Most of the time it is not: there is a concrete, verifiable explanation, and it is written on the bill itself. The problem is that the wrong number is being compared.

This article runs through the seven reasons two neighbouring bills diverge, in order of how much they usually weigh. At the end is the only calculation that makes two bills comparable, and which part of all this a solar system can change.

The first and largest has nothing to do with how much energy you use, but with what each unit costs you.

The residential utilities regime, set out in Ley 142 de 1994, runs on a logic of solidarity: lower estratos receive a subsidy on part of their consumption, and higher estratos, along with commercial and industrial users, pay a solidarity contribution that funds it.

It is not a hidden calculation. It appears as its own line on the bill, negative if you are subsidised and positive if you contribute. Two similar-looking houses can sit in different estratos — stratification is assigned to the property by the municipality — and that alone is enough for the effective price of energy to diverge noticeably.

It is also why the same solar system saves different amounts in two identical houses: savings are kilowatt-hours no longer bought multiplied by what buying them used to cost.

Here is the nuance that causes the most confusion, and it explains why the bill sometimes rises far more than consumption did.

The subsidy does not cover everything you use: it applies up to a threshold, the subsistence consumption, set by the Ministry of Mines and Energy and not the same across the country, because it depends on the municipality's altitude. Whatever you consume above that threshold is billed without subsidy.

The consequence is that a subsidised home has two prices living inside the same bill: some cheap kilowatt-hours and some expensive ones. A month with slightly higher consumption can push a larger share of the spend into the unsubsidised band, and the bill grows faster than the consumption did.

Your neighbour may be in the same estrato as you and still stay under the threshold while you cross it every month. Same nominal tariff, very different bill.

The most obvious reason tends to be looked at last, and it nearly always contributes something: the two houses do not use the same amount.

Air conditioning, an electric shower, a water pump, the old fridge in the back kitchen, the garage door motor, and a house with someone working from home versus one empty from nine to six produce consumption that diverges far more than people estimate by eye.

The place to check is not the current month but the consumption history chart that almost every bill prints. That shows whether your consumption is stable or has been climbing for months, which is the difference between a strange charge and a new habit.

If the chart shows a step that starts in a specific month, there is nearly always an identifiable culprit: a new appliance, a repair, one more tenant in the house, or a faulty unit left running.

In Colombia the energy reaching your home is sold by a retailer and transported by a grid operator, and neither is the same across the country.

The tariff you pay incorporates components that depend on that geography and that company: the cost of the generation purchased, transmission, distribution in your area, recognised losses, and retailing. Two neighbouring municipalities can be served by different operators, with different cost structures.

That is why comparing your bill with a relative's in another city is of little value, and why any article publishing 'the tariff in Colombia' as a single number is simplifying something that is not single.

Within one block this reason rarely applies, but it is the one that explains the big differences between regions.

Two administrative causes explain a huge share of 'odd' months and have nothing to do with consumption.

The first is the length of the period. Billing cycles do not match the calendar month and they do not all have the same number of days. A thirty-three-day cycle bills more energy than a twenty-eight-day one even if your habits have not changed at all, and your neighbour may be on a different cycle.

The second is the meter reading. When a reading cannot be taken, consumption is estimated from the history and adjusted in the following period. That produces the classic pattern of an abnormally low month followed by an abnormally high one, which is not a billing error but the correction of the earlier estimate.

Before complaining, it is worth checking two figures printed on the bill itself: how many days the period covers, and whether the reading was actual or estimated.

The electricity bill is also a collection vehicle for items that are not energy, and that is one reason comparing totals means nothing.

Public lighting is the most common case: it is a municipal tax collected through the bill and calculated on each municipality's own criteria, not on your kilowatt-hours. In many places waste collection rides along too. And on plenty of Colombian bills there are also instalments for purchases financed through the retailer, which are consumer debt rather than a service.

Two neighbours with the same energy usage can be paying very different totals for this reason alone. And it has an important consequence for anyone assessing solar panels: none of these items disappears with a photovoltaic installation.

Before drawing conclusions, isolate how much of your bill corresponds to the energy service. That is the only block the comparison — and solar — can touch.

Finally, something that appears on no line of the bill but is reflected in all of them: two dwellings that look alike from outside can behave very differently.

In a hot climate, orientation, roof insulation, cross ventilation and how much sun the façades take decide how many hours the air conditioning runs, usually the biggest consumer in the house. A dwelling that heats up more spends more even with the thermostat on the same number.

At altitude the equivalent happens with electric showers and water heating. And in any climate, the number of people and their schedules weigh more than the size of the property.

It is the least cited reason and one of the most decisive, because it cannot be fixed by changing tariff: it is fixed by changing the house or the equipment.

The total payable is not comparable because it mixes different things. The number that is comparable comes from a division.

Take the energy service charge — no public lighting, no waste collection, no instalments for anything — and divide it by the kilowatt-hours consumed in the period. That is your effective price per kWh, with subsidy or contribution already baked in. Have your neighbour do the same with theirs.

With those two numbers in hand the conversation changes completely. If the prices per kWh are similar and the totals are not, the difference is in consumption or in the non-energy items. If the prices per kWh diverge, the explanation lies in the estrato, the subsistence threshold or the retailer.

Do it over twelve months and use the average. A single month can be distorted by a long cycle, an estimated reading or a holiday.

If you got this far looking for a way to pay less, it is worth being precise about what a solar system touches and what it does not.

A grid-connected system reduces the kilowatt-hours you buy. The energy you consume at the moment it is generated saves you the full tariff; what is left over is exported to the grid and offset according to article 25 of Resolución CREG 174 de 2021, as amended by Resolución CREG 101 072 de 2025, at a value that need not match that tariff. That is why two houses with the same system and different schedules save different amounts.

What it does not touch are the non-energy items or the charges tied to staying connected to the grid, which is precisely what you are buying: permanent backup. Hence the bill does not reach zero, and any promise of a 'zero bill' describes something the Colombian scheme does not do.

And hence the practical conclusion: the higher your effective price per kWh, the more each unit you stop buying is worth. That number, the one you have just worked out, is exactly the starting point of any serious savings estimate.

When the numbers still do not add up after all of the above, there is a procedure and it is worth following in order.

The complaint is first submitted to the retailer that issues the bill, which is obliged to respond. If the response does not resolve it, the Superintendencia de Servicios Públicos Domiciliarios is the body that oversees the provision and billing of these services and the next place to turn.

Before filing anything, have the data that supports the complaint to hand: the previous and current readings, the days in the period, the consumption history and the previous period's bill. A complaint with those four elements is resolved far better than one that only says the bill arrived high.