There are two kinds of meter in a building and they answer different questions. The utility meter at the service entrance determines what you are charged. Every meter behind it determines how that charge was caused. Both are useful, neither substitutes for the other, and most of the trouble in submetering projects comes from treating them as interchangeable.
This piece is about the practical differences: what each dataset is authoritative for, where they diverge, and what to do about the divergence.
The utility meter is the only billed truth
The number on your invoice comes from the utility's revenue meter, validated through the utility's own process, and applied to a tariff. Nothing you install downstream changes it. If your submeters total 940,000 kilowatt-hours and the utility billed 1,010,000, you owe for 1,010,000.
That has an implication people resist: submeter data cannot be used to dispute a bill on its own. It can raise the question, and it is often the thing that makes somebody look, but the dispute is settled against the utility's meter and the tariff. Which means a building that wants to check its bills needs the utility record and the rate structure, not only the submeters.
In Ontario, account holders have a route to their own utility interval data under the province's data-sharing rules, which we explain in the Ontario Green Button regulation. That is the dataset a bill check is built on.
Submeters are the only explanation
What the utility meter cannot do is tell you which tenant, which floor, or which system caused the total. Only a meter behind it can. This is why buildings with a single accurate revenue meter and no submetering can see that costs rose 18 percent and have no idea why.
| Question | Utility meter | Submeters |
|---|---|---|
| What are we charged? | Authoritative | Cannot answer |
| Was the rate applied correctly? | Authoritative, with the tariff | Cannot answer |
| Which tenant caused it? | Cannot answer | Authoritative |
| What is running overnight? | Visible if interval data is available | Visible per circuit |
| Did this retrofit work? | Weather and everything else is mixed in | Isolates the affected system |
| What do we recharge each tenant? | Cannot answer | Authoritative, subject to lease terms |
Why the two never quite add up
A submetered building almost always finds that its submeters total less than the utility meter. That is normal, and the gap has a small number of causes worth naming, because the response differs.
- House load. Corridor lighting, elevators, parking, pumps and rooftop equipment often sit on circuits nobody submetered, because they are nobody's tenant load. This is usually the largest part of the gap and it is legitimate.
- Design omissions. A panel that was added later, a circuit that was moved, a tenant fit-out that picked up a feed from somewhere unexpected. This is the part of the gap worth chasing, because it grows.
- Meter failure. A submeter that stopped reporting contributes zero, and if nobody reconciles, a tenant is undercharged indefinitely while the gap looks like ordinary house load.
- Losses. Real but small at building scale, and not a useful explanation for a large discrepancy.
- Timing. The utility's billing period and your submeter export period are rarely the same, so comparing them without aligning the periods produces a difference that is purely an artefact.
"Reconcile every period and report the difference. A gap that is stable is house load. A gap that grows is a fault."
The reconciliation is the single practice that separates a submetering system that keeps working from one that quietly degrades. It takes a query, and without it a failed meter is invisible for months.
Regulation follows the billing, not the wiring
Where the meter sits matters less than what you do with the number. A meter used to work out a charge is regulated under the Electricity and Gas Inspection Act, whose section 9(1) requires it to be verified and sealed before service, with the model approved under section 9(4). A meter used only to inform is not.
Ontario adds a licensing layer on top of the hardware rules for the business of metering and billing individual units. The Ontario Energy Board licenses unit sub-meter providers and binds them to the Unit Sub-Metering Code, and its guidance notes that a provider's "fees and service charges are not regulated by the OEB" even though the billing conduct is. The OEB sets out those consumer-facing details on its unit sub-meter provider page.
The practical takeaway is that a submetering project has two quite different cost profiles depending on a single decision made at the start: are these meters going to produce invoices, or information?
The data architecture that works
Buildings that get lasting value out of both datasets tend to arrive at the same arrangement, whatever software they use.
- The utility record, built from invoices and utility interval data, is the system of record for cost. It is what reporting and budgets are built on.
- The submeter record is the system of record for attribution. It is what recharges and investigations are built on.
- A scheduled reconciliation between the two, per period per meter, with the difference stored rather than discarded.
- Raw data retained on both sides. Derived monthly summaries are convenient and cannot be taken apart again when somebody asks a question you did not anticipate.
- One place where both live, so the question "which tenant drove the peak that set our demand charge" can actually be answered, since the demand charge comes from one dataset and the attribution from the other.
That last point is the whole argument for putting them together. A demand charge is set by a fifteen-minute window at the utility meter. Identifying what was running in that window requires submeter data at the same resolution, aligned to the same clock. Two systems that never talk to each other cannot answer it.
When submetering is not the answer
Submetering has a real cost and it is not always the right next step.
- If you have never looked at your utility interval data, do that first. It is available to account holders, it costs nothing to obtain, and it answers the overnight base load question for the whole building immediately.
- If the goal is to allocate cost among tenants who use energy similarly, an area-based split may be close enough that metering will not change anyone's bill by more than the metering costs.
- If nobody is going to look at the data on a schedule, the meters will be a capital expense that produces a dashboard. The reporting routine is the deliverable, not the hardware.
- If the building is about to be renovated, wait. Submeter placement should follow the final electrical layout, not precede it.
Where it does pay, it pays clearly: mixed-use buildings with very different tenant intensities, buildings with a large shared plant, and any building where somebody is being asked to sign off on a recharge they cannot verify.
For the deeper treatment of each commodity, see electricity submetering and water submetering. For turning submeter interval data into something usable, see submetering and interval data management.
Frequently asked questions
What is the difference between metering and submetering?
Metering usually refers to the utility's revenue meter at the service entrance, which determines what you are billed. Submetering refers to any meter installed behind it to measure part of the building. The utility meter is authoritative for cost; submeters are authoritative for who caused it.
Can submeter data be used to dispute a utility bill?
Not on its own. The bill is settled against the utility's own meter and the applicable tariff. Submeter data often raises the question, but the check itself needs the utility record and the rate structure.
Why do our submeters total less than the utility meter?
Usually house load on circuits nobody submetered, which is legitimate, plus some combination of design omissions, a failed meter, and periods that were not aligned before comparing. A stable gap is house load. A growing gap is a fault worth chasing.
Do submeters have to be approved and verified?
Only if you bill from them. A meter used to obtain the basis of a charge must be verified and sealed before service under the federal Act, and its model must be approved. Information-only submeters carry no such requirement.
Should we submeter before or after getting our utility interval data?
After. Utility interval data is available to account holders at no hardware cost and answers the whole-building questions immediately, including overnight base load. Submetering is the next step when you need to know which part of the building is responsible.