Bitcoin Mining with Solar Power: Economics and Setup

Does bitcoin mining with solar power pay off? Usually only barely, or not at all. Your surplus is not free: you give up the feed-in tariff, and in Germany, Austria and Switzerland that is in the same range as the mining yield of about 7 cents per kWh. It can work when your tariff is low, for example on an old system after 20 years, and when the miner adjusts its power to the surplus.

At midday your solar power flows into the grid for a few cents. This article works out what a kWh of surplus is really worth, how unevenly the sun is spread over the year, how to couple a miner to the surplus and what is left in the end for a typical 10 kWp system. Whether mining pays off with normal household electricity is covered in Bitcoin mining at home; the short answer is no.

What a kWh earns in a miner

For solar power, a single number decides: how many sats a miner makes from one kWh. It depends on the efficiency of the machine, measured in joules per terahash (J/TH), and on the state of the network: hashrate, reward per block, price.

With the figures of 13.11.2026 (about 930 EH/s hashrate, 3.149 BTC per block including fees, 2% pool fee):

The more efficient the machine, the more each kWh is worth. Starting today with a used machine of the previous generation gets you clearly less per kWh. What to look for when buying one is explained in Buying an ASIC miner.

These 7 cents are not a fixed price. If the network's hashrate rises, the value falls. At the next halving, roughly in spring 2028, it drops to about half, because the new bitcoin per block fall from 3.125 to 1.5625 BTC.

The true price of the surplus: the feed-in tariff

Power you mine with is power you don't feed in. The tariff you give up is your electricity cost for mining. Economists call this the opportunity cost. It differs a lot by country and by the age of the system.

Three cases deserve a closer look:

• Post-20-year systems in Germany. After 20 years the fixed EEG tariff ends. From then on you only get the market value of solar power, and at midday it is often low. This is where mining is most likely to come out ahead.
• Negative electricity prices. Since the 2025 Solarspitzengesetz (solar peak law), new German systems get no payment for hours with a negative exchange price. Such hours occur mainly on sunny weekends in spring and summer, by now several hundred a year. Your surplus is then genuinely free.
• Austria. There is no fixed statutory tariff for small systems. You sell to OeMAG at the market price or to a utility.

The winter gap: when the surplus occurs

A solar system in Central Europe produces almost three quarters of its annual yield between April and September. Take a 10 kWp system that delivers about 9’500 kWh a year in Germany (about 950 kWh per kWp; southern Germany, Austria and Switzerland are often a bit higher, the north a bit lower):

In December the system produces less per day than a household uses. No surplus is left for a miner. In June it delivers more than six times as much, and at midday far more than the house needs.

This has two consequences:

1. Your miner stands still in winter. It runs mainly from April to September, and then mainly between 10 am and 4 pm. Expect a few hundred to just over a thousand full-load hours a year, not 8’760.
2. The heat comes at the wrong time. A miner turns almost all of its power into heat. In winter you could use it for heating, but then there is hardly any sun. In summer it is there when you need to get rid of it.

Matching the miner to the surplus

The surplus is not a fixed amount. It rises in the morning, varies with every cloud and falls again in the afternoon. A machine that only knows fully on or fully off uses little of it.

Small, large or adjustable

• Large machine (around 3.5 kW): Runs only when at least 3.5 kW are left over. With 10 kWp that is only the case on clear middays in the summer half of the year. With clouds you have to switch it off or buy grid power, which costs 25 to 37 cents.
• Small machine (under 1 kW): Finds enough surplus much more often and runs many more hours. But it is usually less efficient and gets fewer sats out of each kWh.
• Adjustable machine: Many ASICs can be set to a power limit with suitable firmware, for example between a third and full power. Throttled, they even work a little more efficiently. Such a machine follows the surplus and absorbs the most of it.

Smart switching in practice

For the miner to run only on surplus, you need a measurement and a switch:

1. Measure: Your inverter or a meter at the grid connection that measures feed-in provides the surplus. Many inverters expose these values through a local interface.
2. Decide: An energy manager or home automation system compares the surplus with the miner's power. Let it switch on only once the surplus has been stable for a few minutes, and set a minimum run time. Otherwise it switches with every cloud.
3. Switch: The gentlest way is to pause the miner through its software or change its power limit. A contactor that cuts the power hard works, but puts more strain on the power supply and fans.

The order of consumers matters just as much. The miner goes last: first the household, then the battery, electric car, hot water or heat pump, and only what is still left goes into the miner. Every kWh you use yourself saves you the full grid price of 25 to 37 cents. The miner brings 7.

Worked example: 10 kWp system with a miner

The example shows the pattern: depending on the tariff, running the machine ends a few dozen to just over a hundred euros in the black or in the red. That is not enough to buy a new machine, but rather more so for a machine you already own and a low tariff.

Run the numbers with your own figures. Enter your feed-in tariff as the electricity price. Because the calculator assumes round-the-clock operation, multiply hashrate and watts by the share of hours your miner runs: at 1’150 full-load hours that is about 13% (1’150 ÷ 8’760). The line "Pays off up to a power price of" shows you the threshold per kWh regardless:

Noise, heat and connection

A miner on solar runs mainly on summer days. That is exactly when noise and heat bother you most.

• Noise: Air-cooled professional machines reach around 75 dB, as loud as a vacuum cleaner. In the basement, the garage or a soundproofed box that works, next to the bedroom it does not. Small machines and water-cooled versions are much quieter.
• Heat: 3.5 kW of waste heat quickly heats a small room to over 40 degrees in summer. You need an exhaust to the outside. A sensible use is hot water: with water-cooled machines the heat can preheat a buffer tank.
• Connection: A 3.5 kW machine belongs on its own circuit, installed by a qualified electrician. A normal Swiss socket (type 13) is rated for 10 A, about 2.3 kW, and a German Schuko socket is not meant for hours of full load near 16 A either.

Whether mining wastes energy or puts surpluses to good use is discussed in Bitcoin's energy consumption.

Taxes: mining income is income

Bitcoin from solar power are also income when received, valued at the price on the day the pool credits them to you.

• Germany: The tax exemption for small solar systems up to 30 kWp (§ 3 No. 72 EStG) covers the electricity, not the mining. According to the Federal Ministry of Finance letter of 06.03.2025, mining income is business income or other income depending on its scale. Other income has an exemption limit of €256 a year. Because it is a threshold and not an allowance, the whole amount becomes taxable once you exceed it. More in the guide Bitcoin taxes in Germany.
• Austria: Mining income is current income from cryptocurrencies at 27.5%; you cannot deduct power and machine in that case. If you mine as a business, your normal rate applies. Details in Bitcoin taxes in Austria.
• Switzerland: Mining income is income, at larger scale from self-employment. The bitcoin then belong in the securities register.

In the worked example the income of €283 is already above the German exemption limit. At real scale, a tax adviser is worth it.

Who it suits

Bitcoin mining with solar power can make sense when several points come together:

• Your tariff is well below 7 cents, for example on a post-20-year system or with an exchange-linked tariff with low midday prices.
• Household, battery and electric car are already supplied, and surplus is still regularly left over.
• You have an efficient, adjustable machine, ideally one you already own, and a room where noise and heat bother no one.
• You enjoy technology and home automation. Part of the return is understanding how mining works.

If one of these is missing, buying directly is usually better: the roughly €300 of feed-in tariff from the example buys even slightly more sats than the miner finds in a year, without machine, noise and a tax return for mining.