How to Quote Commercial Solar and Battery From a Bill

In short: the fastest way to learn how to quote commercial solar is to work backwards from the electricity bill, not forwards from the roof. Pull the TOU rates, demand charge, and daily charges off the bill, build a consumption profile (interval data if you have it, a shaped template if you don’t), model production against local weather data by roof face, then run solar-only and solar + battery scenarios side by side with the battery dispatched hour by hour against the load. Fold in the incentives, sanity-check the output, and send an Analysis deck first. Done properly, that whole sequence – bill to a credible estimate – takes about ten minutes.

1. What to Pull Off the Bill

Everything downstream depends on six numbers, and they are all sitting on the customer’s existing bill. Before you touch a sizing tool, extract:

• Time-of-use rates in c/kWh. Peak, shoulder, and off-peak, plus the hours each band covers. Peak commonly runs 30–45 c/kWh, off-peak 12–20 c/kWh, and the exact windows vary by network and retailer.
• The demand rate, in $/kW/month (or $/kVA). Typical commercial demand rates sit between $10 and $25/kW/month, and on a site with a real peak, this line can be 30–50% of the total bill – bigger than the usage charge you might assume drives the quote.
• Daily supply charges ($1–$3/day typically). Solar never touches these; they set the floor the bill can’t fall below no matter how the system is sized.
• The NMI, so any interval data you load later can be cross-checked against the right meter.
• Billing days for the period, to annualise correctly rather than assuming a flat 30-day month.
• kWh by period – how much of the bill’s usage actually fell in each TOU band. This is what tells you whether the site’s load lines up with solar hours or not.

If any of that is unclear on the page in front of you, our guide to reading a commercial electricity bill walks through every line item and which ones solar can and can’t move.

2. Build the Consumption Profile

A tariff tells you the price. It doesn’t tell you the shape of the load, and shape is what decides self-consumption. There are two starting points, and which one you use depends entirely on what the customer can hand you.

No interval data yet. This is the common case at first contact. Start from a consumption template shaped to the site type and its opening hours – a day-shift warehouse, a 9-to-5 office, and a 7-day retail store all draw very differently across the day even at the same annual kWh, and a flat or average profile will size the system wrong for any of them. Match the template to the business, then adjust it against the bill’s own kWh-by-period split from step 1 so the shaped profile actually reconciles with what the customer is being charged.

Interval data available. If the retailer or the site’s meter can supply 5, 15, or 30-minute interval readings, use them. This is the difference between an estimate and a measured system: every hour of the year is real, not assumed. Our consumption upload guide covers every file shape the upload accepts (vertical CSV, horizontal CSV, raw NEM12, multi-tab Excel) and how to fix the common errors – stacked registers, unmapped columns, a net-vs-gross mismatch when the site already has solar.

Either way, look at the shape before you size anything. Daytime load is what solar can offset directly. Evening load is what a battery would need to cover. A site that closes at 3 pm and a site that runs until 10 pm can carry the same annual kWh and need completely different systems.

3. Model Production by Roof Face

With the load shape settled, the other half of the picture is what the roof can actually produce. This is where local weather data does the work: a production model run against TMY (typical meteorological year) weather for the site’s location, not a flat national average, because Zone 3 sites (Sydney, Brisbane, Perth, Adelaide, around 4.5 peak sun hours/day) and Zone 4 sites (Melbourne, Hobart, closer to 3.8) generate meaningfully different annual kWh per installed kW.

Work in roof faces, not panels. A commercial roof is rarely one flat plane: a warehouse might have a north face and an east face at different pitches, and each face has its own azimuth, tilt, and shaded area that changes what it can produce. Detect or draw the faces, split the system size across them by area, and let the model run each face against the weather data separately before summing the output. Individual panel placement isn’t the job at this stage – the face-level split is what a first-pass commercial estimate needs, and it’s enough to separate a credible system size from a rough guess.

4. Run Solar-Only vs Solar + Battery Scenarios

Never quote a single system size. Run a sizing matrix: every solar size crossed with every battery size, each combination modelled hour-by-hour against the site’s actual consumption profile. The battery isn’t a flat capex-versus-savings guess bolted on afterward – it’s dispatched hour by hour against the load, so its contribution to demand-charge reduction, peak/off-peak arbitrage, and captured export is modelled the same way the solar is.

Reading the matrix is a matter of picking the right lens for the conversation you’re having with the customer, because “best system” isn’t one number:

• Best overall balance – the size whose export share lands closest to the site’s target, big enough to cover most daytime load without dumping a large share of generation to the grid at a low feed-in rate.
• Best lifetime value – the highest net present value, usually a larger system that trades a slower payback for more total dollars.
• Best incentive uplift – the largest system still inside the scheme-eligible size bands, which is why so many commercial systems land at 99 kW rather than 101 kW.
• Most grid-independent – the highest self-sufficiency among the sizes that are still NPV-positive.

For each of those, compare the solar-only version against the same size with a battery attached. A battery only earns its place on the recommendation when it lifts self-consumption meaningfully over the same-solar, no-battery case – otherwise it’s a token battery sized to bank a subsidy, not to change the site’s bill.

Worked Example: A 120 MWh/yr Warehouse

Take a warehouse consuming 120,000 kWh a year, day-shift operation, on a TOU tariff of 28 c/kWh peak and 18 c/kWh off-peak, a demand charge of $15/kW/month against a 40 kW billed peak, and a $2/day supply charge. Assume 60% of the annual kWh falls in the peak window and 40% off-peak – a reasonable split for a day-shift site, and exactly the kind of number step 1 pulls straight off the bill.

Usage: 72,000 kWh × $0.28 + 48,000 kWh × $0.18 = $20,160 + $8,640 = $28,800
Demand: 40 kW × $15/kW × 12 months = $7,200
Daily: 365 × $2 = $730
Baseline annual bill: $36,730

Now size a 99 kW system (the LGC-threshold sizing habit from step 4, above), on a Zone 4 site at 3.8 peak sun hours/day: 99 × 3.8 × 365 × 0.77 ≈ 106,000 kWh/yr. Assume solar-only self-consumption of 50% (53,000 kWh, avoiding grid purchases at the peak rate since the day shift overlaps solar hours) and 50% export (53,000 kWh at a 6 c/kWh feed-in rate), plus a firm demand reduction of 15 kW (some loading-dock spikes still fall outside solar hours, so the reduction isn’t the full nameplate).

Add a 100 kWh battery. It captures half of the remaining export (26,500 kWh), delivers it back at roughly 90% round-trip efficiency (23,850 kWh usable) into peak-rate grid draw later in the day, and shaves a further 5 kW off the billed peak.

The battery’s own contribution is the gap between the last two columns: $5,988 a year, on top of what solar alone delivers, from a mix of captured export, demand shaving, and arbitrage. That is the number to weigh against an installed battery quote, not the total bill saving, which solar is already doing most of the work on. Every figure above is a stated, illustrative assumption – a real quote runs the same arithmetic against the site’s actual interval data and TMY-modelled production, not a round 60/40 TOU split.

5. Fold In the Incentives

Five schemes typically apply to a commercial solar + battery quote, and getting the eligibility boundaries right matters more than the exact dollar figure:

• STCs for the solar system up to 100 kW, zone-rated by postcode and deeming down to zero at 2030. Run the exact figure on the STC calculator.
• Battery STCs (the federal Cheaper Home Batteries Program, open to small businesses despite the name) work through the same STC mechanism, crediting the first 50 kWh of usable capacity on an eligible battery. Some tools label the line item bSTC; the calculator is at cheaper-home-batteries-calculator.
• LGCs apply above the 100 kW STC threshold, earned annually against metered generation rather than deemed upfront – part of why a 99 kW system is such a common sizing choice. See the LGC calculator.
• VEECs apply only in Victoria, for systems between 30 and 200 kWp, and are mutually exclusive with STCs on the same system – check the VEEC calculator.
• PDRS (NSW) has shifted: the old upfront battery discount was suspended to avoid double-dipping with the federal battery program, and what remains is an ongoing incentive for connecting an eligible battery to an approved virtual power plant. Estimate it on the PDRS calculator.

The full picture, including how the schemes stack, sits on the solar incentives hub and its stacking guide.

6. Sanity-Check Before You Send

Before a scenario leaves your desk, run three checks against it:

• Payback range. Does the number sit near comparable sites, or has one input (an inflated demand reduction, an LGC price that’s stale) done all the work? A payback that leans heavily on one revenue line is the first thing a customer’s accountant will find.
• Export share. In the worked example above, the solar-only system exports 50% of what it generates; the battery pulls that down to 25%. A high export share on a site with cheap feed-in is a flag that the system may be oversized for its load, not a badge of a big system.
• Demand reduction assumptions. Firm reduction should come from where the site’s peaks actually occur, not the nameplate kW of the array. Sizing a demand saving off the panel rating instead of the load profile is the most common way a commercial quote overstates itself.

The demand-charge piece deserves its own read if you want the full mechanics of why solar and batteries move that line differently to usage charges – see demand charges and solar.

7. What to Send: Analysis Deck First, Proposal Once Sizing Is Agreed

Don’t skip straight to a branded proposal. Send an Analysis deck first – the solar and battery scenarios side by side, the sizing matrix, until the sizing makes sense to the customer. That’s the size-up conversation, and it exports as a PPTX deck. Once the sizing is agreed, move to Proposal: detailed tariff pricing, roof faces, and a branded, editable PowerPoint proposal built for signature. Sending the full priced document before sizing is settled means re-doing it every time the customer wants to see one more scenario.

Amperage is built around exactly this sequence: bill in, sized scenarios out, an Analysis deck to align on the system, then a Proposal once it’s time to price and send. If you want to see the bill-to-estimate workflow end to end rather than piece it together from a spreadsheet, book a demo.

Where to Go From Here

Quoting commercial solar and battery from a bill is a repeatable sequence: extract the tariff, build or upload the consumption profile, model production by roof face, run the sizing matrix with the battery dispatched hourly, fold in the incentives, sanity-check the output, and send the right document for the stage you’re at.

First-project walkthrough – the five stages in the app, in order →

How the sizing matrix picks its recommended scenarios →

Calculate your own commercial solar payback →