Battery storage or Bitcoin miner: which uses solar surplus better?

1. Different functions

The battery preserves electrical flexibility: stored power can later serve the building or heat pump. A miner converts power immediately into computation and heat.

High evening demand often favours storage. Persistent heat demand and otherwise unused surplus may justify examining a flexible heat-producing load.

2. Compare six criteria

Assess demand, time flexibility, efficiency, investment, technical risk and revenue uncertainty.

3. Include opportunity cost

For both options, include the value of electricity that would otherwise be exported. A battery also avoids later expensive import. A miner adds net mining revenue and only the heat cost it genuinely displaces, then subtracts hardware and operation.

Do not assign a high heat value where there is no simultaneous heat demand.

4. Combine rather than choose

Larger systems may charge the battery to a target and then send residual surplus to heat. Priorities can change with season and tariff.

A combination increases control and capital cost and is better only if both assets are used sufficiently.

5. Practical decision rule

A battery is usually the more direct fit where evening demand, electrical flexibility or backup are required and regular cycling is expected. Mining with heat recovery requires significant surplus, a useful heat sink, professional infrastructure and accepted financial risk.

• Measure electricity and heat demand first.
• Assign an alternative value to every kWh.
• Review seasonal utilisation.
• Address safety and tax separately.