Solar Self-Consumption vs Peak Shaving: Which Battery Strategy Delivers Better ROI for Your Site?
When businesses first investigate adding a battery to an existing solar system, two strategies typically dominate the conversation: solar self-consumption and peak demand shaving. Both are legitimate value streams. Both can deliver meaningful financial returns.
But they are not the same thing, they are not equally applicable to every site, and combining them without careful modelling can lead to a system that underperforms on both objectives.
This post explains each strategy clearly, walks through a site example for each, and sets out how to determine which approach or combination is right for your facility.
Strategy 1: Solar Self-Consumption
Solar self-consumption is the simpler of the two concepts to understand. When a commercial site generates solar energy and cannot immediately use all of it, the surplus is typically exported to the grid at the solar feed-in tariff which in most Australian commercial contracts is low, often between $0.03 and $0.08 per kWh.
A battery configured for solar self-consumption stores that surplus during the middle of the day and discharges it in the afternoon and evening, when the solar system is generating less but site loads continue. Instead of earning $0.05 per kWh by exporting and then buying power back at $0.30 per kWh in the evening, the business keeps the energy and uses it internally a net improvement of $0.25 per kWh.
Solar self-consumption works best on sites where the solar system is oversized relative to daytime load meaning significant surplus generation that would otherwise be exported at low rates.
A typical candidate: a warehouse with a large roof-mounted solar system that generates significant surplus from 10am to 2pm, but has high loads in the afternoon shift and evening. A battery sized to capture that midday surplus and discharge through the afternoon could deliver meaningful savings.
Strategy 2: Peak Demand Shaving
Peak demand shaving targets a different line item: the demand charge, calculated on the maximum kW drawn from the grid during the billing period. As discussed in our peak demand post, this charge can represent 30 to 45 per cent of a commercial electricity bill and it is generated by a single peak interval, not overall consumption.
A battery configured for demand management monitors the site's real-time load and discharges automatically when demand approaches the target threshold, limiting the visible peak at the meter. The result is a lower maximum demand figure and a lower demand charge.
Peak demand shaving works best on sites with identifiable, repeating demand peaks particularly start-up events, shift changes, or heavy equipment cycles that occur predictably and can be reliably managed by battery discharge.
A typical candidate: a food processing facility where three large compressors start simultaneously at 6am, creating a demand peak that drives the highest demand reading for the month. A battery that discharges during that 30-minute window reduces the peak and reduces the charge.
Comparing the Financial Returns
The relative return of each strategy depends on site-specific factors that can only be assessed with actual interval data. However, some general principles apply:
When self-consumption tends to win
• Large solar system with significant export
• Low commercial feed-in tariff (below $0.06/kWh)
• High evening retail tariff (above $0.28/kWh)
• Moderate or predictable demand peaks
When peak shaving tends to win
• High demand charges on the tariff structure (above $12/kW per month)
• Identifiable, repeating demand peaks
• Smaller or absent solar system
• High energy intensity loads with start-up or cycling peaks
For many commercial sites, both value streams exist simultaneously and a well-designed BESS with a capable EMS can pursue both, prioritising demand management during peak windows and defaulting to solar self-consumption otherwise.
The Risk of Getting It Wrong
The most common mistake we see in commercial battery projects is a system sized and configured purely for one objective without considering the other. A battery sized only for self-consumption may not have enough capacity to handle peak demand events effectively. A battery optimised purely for peak shaving may sit idle during solar surplus hours, missing value.
The other common error is basing the sizing on solar generation estimates or demand estimates without verifying against real interval data. A 15-minute demand peak that drives a month of charges may not be obvious from monthly billing data alone.
How We Model It at Ottergrid
At Ottergrid, we model both strategies simultaneously against a site's actual interval data. Our energy modelling identifies:
• The actual solar generation profile (or projected profile if the system is proposed, not yet installed)
• The timing and magnitude of demand peaks
• The site's export volume and feed-in rate
• The tariff structure, including demand charge rates and time-of-use windows
From this, we can project the financial return for each strategy individually and for a combined approach and recommend the system size and configuration that delivers the best return for that specific site.
Solar self-consumption and peak demand shaving are both legitimate battery strategies with real financial returns. The right choice and the right battery size depends entirely on your site's load profile, tariff structure, and existing solar configuration.
The starting point is always the same: your data. With 12 months of interval data, we can model the full picture and give you a clear view of what each strategy would deliver.
Ottergrid models both strategies for every site we assess. Share your data and we will show you the numbers.
