The utilities envelope
$210 a month. Set Mar. 7, 2026. Currently wrong, deliberately, until Mar. 6, 2027.
Electricity and gas on one account, water, sewer and refuse on the city bill. Between them they swing from $171 in June to $291 in January, and a budget that moves by $120 depending on the weather is not a budget you can hold in your head. So the envelope is flat and the account absorbs the difference.
The arithmetic
Add the last twelve actual bills, divide by twelve, round to the nearest dollar. That is the whole method. There is no seasonal weighting and no forecast, because we tried a weighted version in the first year and it was worse: it was right about the shape of the year and wrong about the size of it, which is the least useful combination.
| Month | Billed |
|---|---|
| September 2025 | 178 |
| October 2025 | 191 |
| November 2025 | 236 |
| December 2025 | 268 |
| January 2026 | 291 |
| February 2026 | 279 |
| March 2026 | 244 |
| April 2026 | 206 |
| May 2026 | 246 |
| June 2026 | 171 |
| July 2026 | 188 |
| August 2026 | 264 |
| Twelve months | 2,762 |
That is $230 a month on the trailing twelve, against a $210 envelope. The envelope is $210 because it was set in March against the twelve months ending in February, which were a milder run. It is now $20 light and it has finished over in each of the last four months.
We are not changing it. The rule is that the envelopes move once a year and this is exactly the situation the rule is for — an envelope that is visibly, arguably, only‑slightly wrong. Every envelope is only‑slightly wrong at some point in the year, and a budget you renegotiate whenever it chafes is a budget that only ever gets larger. March will pick it up.
What we did instead
Two things, both cheap. The furnace filter is now changed on a schedule rather than when someone notices, which the utility's own audit claimed is worth about 5 percent in winter and which we cannot verify but which costs $34 a year to comply with. And the water heater is on a timer that keeps it off between 11pm and 5am, saving something in the region of $6 a month, a figure we arrived at by comparing two Februarys and which we would not defend hard.
The larger available saving is a heat pump, which the landlord will not fund and we will not fund on a twelve‑month lease. That is the honest end of this page: the envelope is $230 a month of weather and we control almost none of it.