Faulty electricity or water meter: who has to prove what

What a meter accuracy test is and why it matters

A “contraste” (accuracy test, sometimes called contrastación) is the technical test used to determine whether an electricity or water meter is registering consumption correctly, within allowed error margins, or whether it’s malfunctioning and causing a bill that’s higher (or lower) than actual usage. It’s the central tool when a customer suspects the device itself — not their real consumption — is behind an unusually high bill.

For electricity, OSINERGMIN’s Guía Orientativa para Reclamos y Apelación states that, once the challenge stage of the complaint has begun, “la empresa distribuidora está obligada a informar al usuario sobre su derecho a solicitar la prueba técnica de verificación posterior del medidor, antes contrastación del medidor” (the distribution company must inform the user of their right to request the technical post-installation verification test of the meter, formerly called the meter contrast test). For water, under SUNASS’s Reglamento General de Reclamos de Usuarios de Servicios de Saneamiento (Article 15, text I could only confirm through a mirror copy, not the official site), “la contrastación del medidor como medio de prueba se aplica únicamente al caso de reclamos por consumo elevado” (meter testing as evidence applies only to high-consumption complaints).

How to request a meter test

Electricity (OSINERGMIN / distribution company): the process starts with a complaint filed with your distribution company (Enel, Luz del Sur, Electro Perú or others depending on your area), explicitly requesting a review and accuracy test of the meter. The company must schedule the test using calibrated equipment. Under Question 2.13 of the guide cited above, the company must inform you of this right once you file a timely challenge to the ruling on your complaint.

Water (SUNASS / your local EPS, such as Sedapal): the complaint is filed directly with your EPS (sanitation service provider). Under the SUNASS regulation, meter testing mainly applies when the complaint is about unusually high consumption, and in cases where tampering or damage is suspected, “la EPS o el reclamante podrán solicitar que la prueba de contraste sea complementada con la verificación del estado de los mecanismos internos” (the utility or the complainant may request that the accuracy test be supplemented with a check of the meter’s internal mechanisms).

Who pays for the test, and when you get reimbursed

For electricity, OSINERGMIN’s official guide (Question 2.15) says that “pruebas similares al contraste” (tests similar to the contraste: technical tests on the metering system carried out without a firm authorized by INACAL, which the guide provides for in some cases where the user does not accept the contraste) “se realizan, en su caso, a costo de la empresa distribuidora” (are carried out, as applicable, at the cost of the distribution company). The guide does not say who pays for the formal contraste you request, so do not assume it is free: ask the company about the cost before accepting it and get the answer in writing.

For water, the reported pattern (though from a single mirror source I could not verify directly on SUNASS’s official site) is more nuanced: if the test is done by the EPS itself, “ésta asumirá el costo de la contrastación” (the utility bears the cost of the test). But if the customer instead hires an independent private testing company on their own, “el costo será asumido por el usuario si la prueba determina que el medidor no sobre-registra” — meaning if you pay out of pocket for a private test and it turns out the meter was in fact accurate, you bear that cost. However, if the meter does turn out defective or tampered with and under-registers consumption, the same source states that “sólo por una vez en un período de cinco años, la EPS asumirá el costo de la reparación” (only once every five years will the utility cover the repair cost), suggesting repeat repairs within that window might not be automatically covered.

A point I could not verify with an explicit rule: I did not find an article stating in clear terms that “if the meter is found defective, the company must reimburse whatever the customer already paid in addition to covering the test cost.” What is confirmed is that, for water, the utility bears the cost when it performs the test itself, and that for electricity, tests similar to the contraste are at the distribution company’s cost. If your case involves reimbursement of money already paid, insist that this be documented in writing in your complaint’s resolution.

What error margin makes a meter “defective”

Electricity meters aren’t perfect instruments: Peru’s metrology standard (INACAL’s Verification Procedure PV-001, based on standard NMP 021:2015, equivalent to the international standard IEC 62058-31:2008) sets error limits by meter class:

• Static meters, class 0.2S: between ±0.3% and ±0.4% error, depending on the test point.
• Static meters, class 0.5S: between ±0.6% and ±1.0%.
• Static meters, class 1: between ±1.0% and ±1.5%.
• Static meters, class 2: between ±2.0% and ±2.5%.
• Electromechanical meters, class 2 (older spinning-disc type): up to ±3.5% at low currents, ±2.5% at rated current, and ±3.0% at power factor 0.5 inductive.

If the accuracy test result falls within these ranges, the meter is considered technically correct and a faulty-meter complaint normally does not succeed on that basis (though a separate high-consumption complaint may still proceed through other channels, such as checking for leaks or internal wiring issues). If the result exceeds those limits, “el medidor ensayado debe cumplir satisfactoriamente con todos los requisitos establecidos” (the tested meter must satisfactorily meet all established requirements); otherwise it is recorded as non-compliant on the test certificate, which supports your complaint.

For water meters, I did not find an equivalent tolerance table confirmed in an open official source. If your case hinges on that exact figure, ask your EPS or SUNASS to show you the technical testing standard that applies to your specific meter.

What happens to your bill while the dispute is pending

This is where public information is thinnest. What is confirmed in both sectors is that the utility cannot cut your service for non-payment of the disputed amount while the complaint is being processed: for electricity, once a complaint is filed the company cannot “cortar el servicio sobre la base de la falta de pago de los recibos objeto de reclamo, en tanto éste no haya sido resuelto en última instancia administrativa” (cut service over non-payment of the bills under complaint until it has been resolved at the final administrative level); for water, “ninguna EPS podrá disponer el cierre del servicio si éste se fundamenta en la falta de pago de los montos y conceptos reclamados” (no EPS may order a service shutoff based on non-payment of the amounts and items under complaint).

However, I did not find an official provision stating explicitly whether, during that period, the utility must bill you based on your historical average consumption or based on the higher disputed reading. This remains an unconfirmed point: in practice, many customers report continuing to receive bills reflecting the disputed reading (not an average), but without that amount being enforceable while the complaint stays open. If your utility demands full payment of the disputed amount under threat of cutoff, that could itself be grounds for an additional complaint.

What to do if the utility refuses to test the meter

If the company rejects your request for a test, delays it without justification, or resolves the complaint without having performed the test, you have the right to appeal. For electricity, the confirmed deadline is 15 business days, counted from when you receive the electricity company’s ruling, to appeal to OSINERGMIN’s JARU (Junta de Apelaciones de Reclamos de Usuario), described as an “organismo independiente” (independent body) within the regulatory structure. For water, the equivalent body is SUNASS, through its administrative appeals board; I could not confirm whether the 15-business-day deadline is identical for this sector, so check the exact deadline stated in your own complaint resolution.

Keep copies of all your documentation — the original complaint, the request for the accuracy test, any company response, and your case number — since these form the basis for any subsequent appeal.