  In the last few years, electric utility companies have increasingly invested
into transactive energy systems. This trend was primarily caused by the
integration of distributed energy resources (DERs) and internet-of-things (IoT)
devices into their existing distribution networks. Influenced by the general
interest in blockchain technologies, many industry specialists are considering
new, more efficient peer-to-peer market structures for DERs. Since
blockchain-based energy exchanges can automate transactions between their
members and provide increased levels of security thanks to smart contracts,
these new initiatives may eventually revolutionize how customers interact with
utility companies. In this paper, we explore the trade-off between cost and
traceability in the form of on-chain and off-chain solutions. We also propose
ZipZap, a first step towards a blockchain-based local smart grid system. ZipZap
is an ERC-1155 compliant solution with four different prototypes: Heavyweight,
Featherweight, Lightweight and Weightless. The first three prototypes were
developed in Solidity and deployed using Ethereum. Heavyweight is fully
on-chain, whereas Featherweight and Lightweight showcase various levels of
hybridization. Weightless, in turn, was deployed using Quorum, a gas-free
alternative to Ethereum. Our evaluation uses realistic parameters and measures
the impact of different types of metadata storage scopes, with some Ethereum
prototypes showcasing gas cost reductions of more than 97% in comparison to our
fully on-chain baseline.
