Demand charges require interval data, not just monthly kWh
Many commercial tariffs charge partly for the highest measured demand during a billing window. Two sites with the same monthly energy use can therefore have very different bills if one has a sharp peak. Before sizing a battery, obtain the actual tariff and interval load data at the meter resolution used for billing. Identify seasonal rules, ratchets and whether the demand charge applies during all hours or defined periods.
Solar reduces a peak only when production overlaps it
A daytime commercial load may align well with PV, but late-afternoon, morning or weather-driven peaks can remain. Model PV production and site demand on the same time interval. A large annual solar offset does not prove that demand charges will fall. Export limits can also change the value of adding more PV once midday load is already covered.
Battery power controls how much of a peak can be shaved
Peak shaving is a kW problem first: the battery inverter must discharge fast enough to keep grid demand below the target. Battery energy in kWh determines how long that discharge can continue. A short high peak and a long plateau may need very different battery designs even if their maximum kW is identical.
Control logic must preserve enough state of charge
A battery that has already discharged for energy arbitrage may not have enough reserve when the billing peak arrives. The energy-management strategy should prioritise the economic objective explicitly and account for forecast uncertainty. Backup reserves add another constraint. Use the capacity-versus-power guide as a conceptual reference, while commercial design should use measured site data.
Tariff savings must be compared with cycling cost and constraints
Frequent high-power cycling can affect warranty throughput and usable life. Include battery efficiency, degradation assumptions, warranty limits and any utility program rules in the financial model. A projected demand-charge saving should be traceable to the actual tariff and interval simulation rather than a generic percentage claim.
Plan measurement and verification before commissioning
After installation, track grid demand, battery commands, state of charge and PV output at sufficient resolution to verify that the control target is being met. Document the baseline period and any major operational changes at the facility. For procurement, combine this analysis with Melnti’s quote comparison checklist so competing proposals use comparable assumptions.