Incredibly, one totally cleared acre of ideal land can fit as many as 2,000 standard solar panels. That said, the number of panels that will fit depends on a wide range of variables. Most of all of course, it depends on how big the solar panels are. The most common solar panels are 100-300 watts, which produce 300-1200 watts per day depending on the size and weather. A standard design panel of this size will require about 2 square meters or 20 square feet of space on your land. Since an acre is around 43,000 square feet, the total number of these typical panels that you can fit should be just over 2,000. These panels should produce around 250 KWs of solar power.
There are other factors to consider, however. You might want larger solar panels, in which case you of course would not be able to fit as many panels on a single acre. Many solar farms prefer to angle the panels rather than laying them flat. This technique maximizes sunlight exposure, but takes up more space. Angling typical 100-300 watt solar panels will reduce the number of panels you can fit on one acre by about 20-25%, meaning that your total number of panels per acre will be closer to 1500.
The type of land your acre is on will also make a big difference. Not all land has the right terrain for maximizing solar panel count, and some land is not fully cleared. Finally, of course, you will need to pay for a way to store the energy produced by your panels on top of installation and maintenance costs, which might affect the number of panels you can install in a given area. That said, solar energy has a wide range of benefits, so it makes sense to install as many solar panels on one acre as necessary for meeting your energy goals.