Thermal storage energy management
The battery you already own.
Make your home smart enough to dodge the big energy bills.
Your house and its hot-water tank already store energy as heat. WattDodger decides when to fill them — on cheap night power and free rooftop solar — and lets the house coast through expensive peak periods on the heat it already holds. No new battery. No new hardware.
Running today on live houses in the Wairarapa, New Zealand.
The problem
Peak power is expensive. Batteries are expensive. Your house is already a battery.
You buy power at the worst time
A thermostat heats when the house gets cold — which is the cold morning and the dark evening, exactly when a time-of-use tariff charges the most.
Your solar is sold cheap, bought back dear
Midday export earns a few cents. That same energy costs several times more when you buy it back at 6pm to run the heat pump.
A home battery costs five figures
It's a lot of capital to shift a few kilowatt-hours. Meanwhile the concrete slab and the hot-water cylinder you already paid for sit unused as storage.
How it works
Charge when power is cheap or free. Coast when it isn't.
Heat is energy, and a warm building loses it slowly. WattDodger treats the building fabric and the hot-water tank as one storage system, and schedules the heat pump against tomorrow's prices, weather and bookings.
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Read the day ahead
Your booking calendar, the weather and solar forecast, and your tariff's peak, shoulder and night windows.
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Charge the stores
Pre-warm the building and bank hot water on cheap night power and your own rooftop solar, before the price climbs.
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Coast through peak
Back off the heat pump while power is expensive. The house lives on the heat it already holds, and stays comfortable.
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Learn the house
Every cycle refines the model of how fast this house heats and cools, so tomorrow's schedule fits it better than today's.
A concrete example. On the reference house, heat is charged on the night rate before the morning peak, and the hot-water tank is banked to target before 7am — so it coasts through peak without a reheat. The self-learned free-cooling time constant is about 18 hours, which means a well-insulated house barely cools between charges.
Why it's different
Control, not capital.
Most "smart energy" products ask you to buy a battery first. WattDodger starts from the storage that is already sitting in your slab, your walls and your cylinder — and spends its intelligence on when to fill it.
- Uses storage you already have. Building mass plus the hot-water tank — zero new hardware compared with a home battery.
- Calendar-driven. It knows when the house is occupied, so it warms for arrival and sleeps when the place is empty.
- Solar, weather and tariff aware. It leans on free PV and the cheap night rate, anticipates warm afternoons, and avoids peak.
- Self-learning. It fits each house's cooling constant and heating rate, so it gets smarter the longer it runs.
- Transparent. A live dashboard shows exactly what it is doing, and what it saved against a flat "dumb thermostat" plan.
- Pioneering the framework. Including a buffer-tank "top-up radiator" pattern that extends how long a house can coast.
Proof
It's built, and it's running.
Not a concept. WattDodger controls a CTC EcoZenith i250 heat pump over Modbus on a live reference property, coordinating Fronius solar and a BYD battery against New Zealand time-of-use tariffs, with further test installs alongside.
Self-learned free-cooling time constant on the reference house — how slowly it gives heat back.
New battery capacity required. The storage is the building and the cylinder.
Thermal mass and hot water, scheduled together as one system.
Model your own savings
The interactive thermal-battery simulator lets you model what load-shifting alone is worth on a house like yours — smart control only, no battery.
Invented here
The buffer-tank top-up radiator
One reference house runs a buffer tank on the radiator circuit with a single always-open "top-up" radiator, sized to offset the building's heat loss. So while the heat pump is busy making hot water, the house still stays warm — extending how long it can coast.
Savings depend on your tariff, your house and your habits. Figures shown on this site and in the simulator are modelled from measured house data — they are typical results, not a guarantee.
Who it's for
One engine. Four kinds of building.
Airbnb hosts
Warm on check-in, asleep between guests — synced to your booking calendar, across every listing.
For short-stay hosts →Bach & holiday-home owners
Your bach, warm when you arrive and dozing when you're not. Tuned to NZ tariffs and Book a Bach calendars.
For bach owners →Home owners
Self-consume your solar, dodge the peak, and cut the power bill without buying a home battery.
For homes →Coming soon
Business & offices
Turn a building's mass into a demand-response asset: pre-condition on cheap power, coast through demand peaks.
Register interest →
WattDodger
Certified
WattDodger Certified
A mark for homes that heat themselves intelligently.
Properties actively managed by WattDodger can carry the Certified mark — a plaque by the door with a QR code. Guests scan it and land on a page for that property, explaining what a smart-controlled home means for their comfort, its running cost, and its carbon.
For hosts it's a visible reason to choose your listing. For guests it's an explanation of why the house is already warm.
Early access
Put your thermal battery to work.
WattDodger is rolling out to its first houses, baches and short-stay rentals in New Zealand. Tell us what you're heating and we'll be in touch as places open up.
Prefer email? lee.mauger@kiwicollaborative.com