The phrase "significant drain" means a substantial reduction or decrease in something, usually in terms of resources, energy, or effectiveness. Full definition
Both features are significant drains on battery life, and I often found myself leaving it charging on my desk with that convenient - yet - somehow - inconvenient microUSB plug. (theverge.com)
While obesity is clearly a serious health problem in the UK, it is not a significant drain on the welfare budget. (politics.co.uk)
Not to mention a significant drain on the pockets of natural gas companies who don't get to bill for the lost gas. (sciencemag.org)