It’s commonly accepted that there are seven forms of renewable or alternative energy: solar, hydroelectric, wind and ocean energy (such as tidal); geothermal (including ground heat pumps); and biomass and hydrogen. Some consider nuclear power to be a ‘green’ energy, but it isn’t from a renewable source.
Some forms of renewable energy, such as wind and solar, do vary in their effectiveness, being dependent on the weather; and hydroelectric can also provide seasonal fluctuations if a dam isn’t providing the water source. However, solar and hydro power can be used together to provide a steadier stream of electricity, as solar tends to provide more output in summer and autumn while hydro delivers more in winter and spring. If managed well, alternative energy can be more reliable than one might expect. Some types of alternative energy, such as anaerobic digestion, can provide reliable electricity and waste heat for heating on a 24/7 basis.
This is a commercial power generation risk, not an office-based combined policy, and the excesses need to be viewed on that basis. An excess is there to remove small and minor losses while allowing policyholders to still be able to protect their main exposures at an affordable price. This ultimately helps keep costs down.