Recovered compute heat.
Lower-temperature readiness.

A compute module uses electricity. Almost all of that electricity becomes heat.

Where the site can use the heat, M4 may support a lower-temperature thermal layer: baseline warmth, pre-warming, changing-room comfort, or another reviewed heat path.

While producing heat, the module can also perform Bitcoin computation.

The heat output is stable. The mining output is variable.

The sauna stove remains the bathing heater. M4 does not replace the stove. It does not provide final bathing temperature, stones, steam, or löyly.

Hamburg is used instead of Munich because it better represents the northern European route-to-market logic for this study.

Wholesale power prices are used for city comparison. They are not customer bills.

A real site cost may include grid fees, taxes, VAT, retail margin, capacity charges, and contract-specific terms.

All schedules use the same historical 1.1 kW assumption for comparison. They do not define the current M4 hardware basis.

Schedule D is a reference case. It is not the intended use case.

The heat side follows electricity input. It does not depend on Bitcoin price.

For a private site, the strongest M4 role is readiness.

A private sauna may sit cold for long periods, especially in winter or shoulder seasons.

When the sauna is started from cold, the stove must heat the cabin air, internal surfaces, glass, benches, and surrounding thermal mass before the bathing range is reached.

M4 can support a lower-temperature baseline before the stove is used.

Remote pre-heat does not mean the sauna is brought to bathing temperature. It means M4 may create a warmer starting condition before use, reducing the temperature gap the stove has to close.

The stove completes the final lift to bathing range.

The private case is mainly about comfort, baseline readiness, remote pre-heat, and reduced cold-start load. It is not a return calculation.

For a professional setting, M4 may have a more operational role.

A retreat, guest site, showroom, or hospitality setting may have more predictable use patterns than a private home.

The site may need warmth earlier, longer, or more often.

M4 can support a reviewed baseline heat layer around booking windows, changing areas, and repeat use.

The professional case is mainly about operating quality. It can support guest readiness, shorter heat-up windows, and a clearer thermal basis. It still depends on site fit.

M4 does not create additional heat beyond its electrical input.

Where M4 heat is captured inside the sauna shell, changing-room area, or another reviewed thermal path, it may reduce the cold-start condition.

The stove then heats the remaining temperature difference to bathing range.

This may reduce heat-up time. It may also reduce stove electricity use during final heat-up.

The effect is not automatic. It depends on outside temperature, insulation, ventilation, thermal mass, heat path, controls, timing of use, and how much of the recovered heat is retained.

For this reason, M4 is reviewed before specification.

This is the thermal basis for cold-start reduction. It should not be added as extra heat. It is the useful portion of the recovered heat.

While M4 produces heat, it can also perform Bitcoin computation. That output is variable.

The model includes the 2020 and 2024 Bitcoin halvings. The mining result should therefore be read as historical. It is not a forward-looking estimate.

The 1.1 kW module power is part of this historical model only. It is not the current M4 hardware basis.

This is not a future yield estimate. It is a historical model. The value is calculated as if mined BTC was valued during the operating year, not held into the future.

In this historical site-power scenario, the dual-use output reduced the effective cost of recovered electric heat by approximately 78%.

That is the case for dual-use heating. Not that heat has no cost. Not that the result repeats. But that the same electricity produced heat and computation during the period studied.

The negative values do not mean the heat had no cost. They mean the estimated compute output was larger than the modelled wholesale electricity input.

A real site must still account for billed electricity, taxes, VAT, grid charges, hardware, maintenance, controls, uptime, noise, ventilation, service access, and operating responsibility.

The model shows three layers of value.

First, M4 produces stable recovered heat because almost all electrical input becomes heat.

Second, where that heat is captured, it may reduce the cold-start condition and support lower-temperature readiness before the stove brings the sauna to bathing temperature.

Third, while producing that heat, the module may also produce variable Bitcoin mining output.

The strongest case is not mining alone. The strongest case is useful heat with a second output.

M4 strengthens SAUNA. where the site needs more than bathing heat.

The stove creates the sauna ritual.

M4 can support the surrounding thermal condition: changing, transition, pre-warming, and lower-temperature readiness.

In private use, the value is comfort, readiness, and a reduced cold-start condition.

In professional use, the value is repeatable baseline warmth, guest readiness, and clearer operating logic.

In both cases, the mining output is secondary.

It may reduce the effective cost of useful recovered heat in some periods.

It is variable and not assured.

The business case is strongest where the site already needs the heat.

M4 is not a replacement for the sauna stove.

It is not a bathing heater.

It is not suitable for every site.

It is not a return promise.

It is an optional recovered compute-heat module for reviewed lower-temperature use, with hardware reviewed through the project basis.

Where the heat has a clear role, the same electricity can produce two outputs: heat and computation.