Sense -> Analyze -> Decide: From IotaWatt to a Home-Battery ROI

A full loop of home energy: measure circuits with an IotaWatt, forecast load and peaks, then decide whether a home battery actually pays for itself.
Author

Benedict Thekkel

Published

June 20, 2026

Home energy is a rare project where you get the whole data lifecycle in one place: sense the real load, analyze / forecast it, then decide on capital kit like a battery. This ties together three repos:

The loop

flowchart LR
  M[IotaWatt CTs] -->|per-circuit W, 5s| DB[(Time series DB)]
  DB --> A[Analyze load profile]
  A --> F[Forecast load + peaks]
  F --> ROI[Battery ROI model]
  ROI --> D{Worth it?}
  D -- yes --> B[Size + buy]
  D -- no --> W[Wait / re-tariff]

Sense: what an IotaWatt gives you

The IotaWatt clamps a CT around each circuit and logs real power every few seconds - no utility meter guesswork. That per-circuit resolution is what makes the later decision honest: you see exactly which loads drive your peaks.

A representative daily load profile - note the morning and evening peaks that a battery would shave:

Analyze + forecast

With history in hand, the TimeSeries_ML Nixtla notebooks forecast both average load and - the number that sizes a battery - the peaks. Peak forecasting matters because demand tariffs and battery sizing both key off the top of the curve, not the mean. See peak forecasting.

Decide: does a battery pay for itself?

The home-battery notebook turns the measured profile + tariffs into a payback. The ROI is dominated by self-consumption - how much stored solar you actually use instead of exporting cheap and buying back dear.

Battery Usable kWh Installed cost Annual saving Payback
Small 5 $6,500 $520 ~12.5 yr
Medium 10 $11,000 $980 ~11 yr
Large 13.5 $14,500 $1,180 ~12 yr

Representative figures; depends heavily on tariff, solar size, and usage.

Self-consumption is the whole game

With the medium battery, modelled self-consumption of on-site solar rises from ~40% to ~78% - that delta is the saving.

Takeaway

Measure before you buy. The IotaWatt turns “a battery feels worth it” into a payback curve you can actually defend - and in my modelling, at current tariffs, the honest answer is often “wait for prices to fall or a demand tariff to bite.” The point is that the data, not the vibe, made the call.

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