A standard 141' (43m) superyacht will run you $2-30Mil. Used.
From Superyacht Times:
Eco-friendly superyacht design serves to inspire designers and clients to turn toward reducing the carbon footprint. We have yet to see how the more experimental designs would fare on the water, however new technology allows for the construction of superyachts with lightweight materials, as well as greener ways of generating energy.
Eco-friendly superyachts have been receiving increasing attention from yachting professionals and the press alike. In an effort to lower carbon emissions new designs have emerged holding both subtle and radical design characteristics.
An example of new a 'green design' is the Formula Zero superyacht concept: a solar hybrid design from Sauter Design. The recently unveiled Formula Zero is created to offer a faster, ergonomic and greener power sailing yacht, with an advertised 75% - 100% reduction in emissions. The design features 800+ square metres of light concentrating wingsails, making it one of the more radical eco-friendly designs available....MORE
Here's the Formula Zero:
Formula Zero employs all of the above to achieve a 75 to 100% reduction in GHG emissions in a 43 metre Solar Hybrid Superyacht that embodies luxurious independence, stylish comfort and superior sea keeping performance.
Richard Sauter head of design commented; “To evaluate Formula Zero as a Carbon Offset Project, we compare a 43 metre catamaran to a 54 metre monohull which is similar in terms of performance, space and accommodations. While both vessels are evenly matched, when cruising for 24 hours, Formula Zero consumes 4,000 litres less fuel, which amounts to a 10 ton per day reduction in CO2 emissions. 10 tons is the amount of CO2 that the average European emits in one year....
And a concept design in U.S. Coast Guard colors.