The June Baseline: Water and Power, Measured

Off-grid systems fail in January. They are diagnosed in January too, which is the problem, because January is the worst possible month to be discovering how your system behaves.

Everything you needed to know was visible in June. June is your best case — longest days, most sun, warmest water, lowest heating draw. If you know what the system does at its best, the winter number is arithmetic. If you only ever look when something goes wrong, you have no baseline to compare against and every problem looks like a new one.

So this is a June job: measure the good month, on purpose, while nothing is going wrong.

Water: four numbers, once a day

Rainfall. A cheap gauge, read at the same time daily. This is your input and it is the number people assume they can get from a forecast afterwards. You cannot — regional rainfall and what landed on your roof are different quantities.

Tank level. At a fixed time, same time every day. The absolute number matters less than the trend, and the trend only exists if the reading time is consistent.

Roughly what you drew. You do not need a meter. “Garden watering twice, laundry, normal household” is a usable entry, because what you are building is a correspondence between activity and drawdown.

Overflow. The number almost nobody records and the most actionable one on the list. Every overflow event is capacity you paid for and lost. Three overflows in a wet June is a straightforward argument for another tank, and it is an argument you can only make if you wrote them down.

Power: production against draw

If you generate, the same principle applies. Record production daily, and record what you actually ran.

The pairing is what matters. A day’s production number alone is a weather report. A day’s production alongside “ran the pump and the freezer, plus laundry” is a system model — and after a month you can predict what a given day supports without guessing.

Note the exceptional days at both ends. The best day of June is your ceiling. The worst day of June — the overcast one — is much closer to an average December day than the good ones are, and it is the most useful single data point you will collect all summer.

The winter arithmetic

Here is why June is the right month.

Once you know your midsummer production and your midsummer draw, the winter question becomes: what is the ratio of December to June for my location and my setup, and what does the draw look like when heating and lighting are added? Both are answerable from a summer baseline plus one winter’s readings.

Without the baseline, you get to December with a system that is struggling and no way to tell whether it is undersized, badly configured, or simply having a bad fortnight.

One month of this is a genuinely useful document. A year of it is the thing you would want if you ever expanded, sold the place, or had to explain the system to someone else.

Vital Inputs is built around exactly these four sections — water, energy, climate and the maintenance log — with the daily lines already ruled so the reading takes seconds rather than requiring a decision about format.

A note on the maintenance column

Add one more thing while you are at it: what you serviced and when. Filters, pumps, gutters cleared, panels washed.

Nothing degrades an off-grid system faster than deferred maintenance that nobody is tracking, because each individual deferral is reasonable and the accumulation is not. A dated maintenance line is the only defence, and June — when everything is working — is when it is easiest to keep.

This month

Put the gauge out, pick a reading time you will actually keep, and start today. Thirty seconds a day for a month.

Come January, when something is marginal, you will have the one thing that makes it diagnosable: a record of what normal looks like.

— Hadley