A two-zone meter is usually sold as "the night rate is cheaper". That is only half true, and the other half is why people feel let down after switching. Here is what actually happens.
One meter, two registers
An ordinary meter has a single total register: one number that grows with every kilowatt-hour. A two-zone meter has two independent registers. The device knows the time of day and adds consumption to whichever register matches the current zone — day or night.
So the "night tariff" is not a discount on your bill. It is a separate bill for a separate slice of consumption. You pay twice at two rates, rather than once at a reduced one.
The practical consequence, up front: the saving depends not on owning a two-zone meter but on what share of your consumption falls into the night zone. If the only thing running at night is the fridge, there is nothing to split.
What the calculation looks like
The mechanics are the same whatever the rates and zone boundaries are:
- Read both values — day and night. The meter labels them separately, often T1 and T2.
- Subtract the previous value of the same register from each. You now have two consumption figures.
- Multiply each by its own rate.
- Add the results. That is the electricity charge.
The most common mistake is in step two: subtracting the previous *total* instead of the previous value of the same register. The registers advance independently and must never be mixed.
A worked example
The numbers below are illustrative: rates differ by region and supplier and they change. Take yours from your own bill or contract — what matters here is the structure, not these figures.
| Register | Previous | Current | Used | Rate (example) | Charge |
|---|---|---|---|---|---|
| Day (T1) | 14,320 | 14,510 | 190 | 4.00 | 760.00 |
| Night (T2) | 6,180 | 6,290 | 110 | 2.00 | 220.00 |
| Total | 300 | 980.00 |
Compare that with single-zone billing at the same day rate: 300 × 4.00 = 1,200.00. The saving here is 220, and all of it rests on the 110 kWh that landed in the night zone. Had the night share been 20 instead of 110, the saving would have been about 40.
When switching does not pay off
A two-zone meter has to be bought and installed, and that cost is repaid only by night consumption. So the sum is simple: multiply your expected night share by the difference between the day and night rates — that is the monthly saving. Divide the installation cost by it and you have the payback period in months.
If that comes out beyond two or three years, look first at whether consumption can be moved into the night zone at all. What genuinely moves:
- a water heater — the largest item, if you heat on a schedule rather than on demand;
- washing machine and dishwasher — most have a delayed start;
- charging an electric vehicle;
- electric heating and underfloor heating with heat storage.
What will not move: lighting, cooking, television, computer — everything you need precisely while you are awake.
The exact zone boundaries and coefficients are set by the regulator and they change, which is why this article deliberately does not state them. Find yours on your bill, in your supply contract, or in your supplier's tariff schedule. The mechanics above do not depend on those numbers.
How this works in Platizhka
In the app a two-zone tariff is set up as a zoned one: you create "day" and "night" zones with your own rates, then enter two readings each month instead of one. The app performs the calculation above and stores it together with the month — so if the rates change later, past charges stay exactly as they were.