---
app_version: 0.1.0
precision: 2
form_title: Electricity bill — back-payment ahead?
form_description: Read your meter today and know months before the bill arrives. Enter the reading from your last bill, today's reading and your tariff to see the projected yearly cost, the expected back-payment or refund, and the monthly advance that would fit.
form_inputs: Meter at last bill|reading_then{kWh}, Meter today|reading_now{kWh}, Days since last bill|days_since, Price per kWh|price{€/kWh}, Base fee per month|base_fee{€}, Monthly advance|advance{€}
form_outputs: Projected use per year|per_year, Projected cost per year|cost_year, Advance paid per year|paid_year, Back-payment (+) or refund (−)|balance, Advance that would fit|fair_advance
---
# Electricity bill — back-payment ahead?
// Read the meter now instead of waiting for the bill. This notebook also has
// a FORM (Pro): Form → Form view for an input mask.

# Meter readings
reading_then = 41250 kWh   // on the last bill
reading_now = 43480 kWh    // read today
days_since = 240           // days between the two readings

# Tariff
price = 0.34 €/kWh
base_fee = 12 €            // per month
advance = 100 €            // what you pay each month

# Projection
// kWh × €/kWh cancels to €, no manual conversion anywhere.
used = reading_now - reading_then
per_year = used / days_since * 365
cost_year = per_year * price + base_fee * 12
paid_year = advance * 12
balance = cost_year - paid_year
fair_advance = cost_year / 12
"Projected use per year": per_year
"Back-payment (+) or refund (−)": balance
"Advance that would fit": fair_advance
// Winter uses more power than summer: a reading taken right after a winter
// overstates the year a little, one taken after a summer understates it.