Why your meter shows two numbers
A multi-tariff (day/night) electricity meter has separate registers: one counts kilowatt-hours used during peak daytime hours, the other during cheaper night hours. The whole point is to reward you for shifting heavy use — washing machine, dishwasher, EV charging — into the cheaper window. But it only saves money if you track each register correctly.
The mistake that inflates your bill
The most common error is reading just the displayed number without checking which register is showing. Many meters cycle between displays (often labelled T1 and T2, or with sun/moon icons). If you log the night value as if it were the day value, every difference and price applied is wrong — and you won't notice until the bill arrives.
So each time you read:
- Note the day (peak) register value.
- Note the night (off-peak) register value.
- Record them as the same date so the math lines up.
Let the difference and pricing be automatic
The actual usage is this period's reading minus last period's — done per register, not on the total. Then each register's kWh is multiplied by its own price. Doing this by hand across changing readings is where people slip up.
In FinMan you set up a service (electricity) under your address and add a tariff of type multi-tariff with day and night prices. Each time you submit readings, it computes the difference for each register and calculates the bill using the matching rate — no spreadsheet, no mental arithmetic.
Tip: Snap a photo of the meter through the bot and let AI read the value, then confirm it's matched to the right register before saving.
When your rate changes
Energy prices move. When your provider updates the day or night rate, you don't overwrite history — you add the new price with its effective date. FinMan keeps tariff changes over time, so past bills stay calculated at the old rate and new readings use the new one. This matters if you ever compare months or check whether off-peak shifting actually paid off.
A quick habit that works
Read your meter on the same day each month, capture both registers in one go, and let the app handle the difference and pricing. Over a few months you'll see exactly how much your night usage saves you — and whether running the dishwasher at 11pm is worth it. Spoiler: it usually is.