Heat storage — storing solar energy directly as thermal mass rather than converting it to electricity and back — is 5 to 10 times cheaper per kWh of storage capacity than battery storage, lasts indefinitely, and requires no electronics, BMS, or inverter. Storage systems turn solar power from a “use it or lose it” resource into a reliable, flexible energy source. Atlas Copco's guide on solar energy storage lays out the basics of thermal, mechanical, and battery storage, and helps readers understand which method works best. Batteries, particularly lithium-ion, are the most common solution for residential applications due to their efficiency and lifecycle. One common method of storing solar energy is through the use of batteries, where excess energy generated by solar panels during the day is stored for later. Different methods of solar energy harvesting use thermal energy for different purposes ranging from individual to commercial and industrial levels.