How much is ADT a month if it's already installed?

If your ADT system is already installed, you are only paying for monitoring and services, not equipment, but the monthly cost still varies widely based on your plan. As of 2026, ADT's basic professional monitoring plans typically start around $28.99 to $32.99 per month for landline or basic wireless monitoring if you own the equipment outright. Most customers with an existing system choose ADT Self Setup or the standard ADT Plus package, which ranges from about $32.99 to $59.99 per month and includes smartphone app control, smart home integration, and 24/7 professional monitoring. If you want video monitoring with cloud storage, higher-tier plans like ADT Complete can run $59.99 to $65.99 per month or more. Customers who originally signed a contract and own their panel outright can often negotiate or stay on legacy rates, but if you were leasing equipment, your monthly fee may be higher even after installation because the equipment cost was amortized into the contract. Always check if you are out of contract, because that gives you leverage to lower your rate.

If your home already has ADT-compatible security hardware installed from a previous owner, activation and monitoring service plans typically cost between $35 and $50 per month. Because you are not financing new equipment, you can often secure basic monitoring tiers without paying heavy upfront hardware costs, though a new monitoring agreement is required. Verification: Call ADT customer support to confirm compatibility and activate monitoring on existing sensors.