Commercial battery proposals are more likely to go ahead when the client can see where the savings come from and how the figures stand up to their questions.
GridVolt’s free simulator helps installers test battery size, savings and payback against the site’s load, tariff, solar and export limits.
Below, we answer the questions commercial solar installers and EPCs face ask us about how to make their battery proposal more persuasive to clients.
What can we safely quote for a commercial battery project before the client provides half-hourly data?
Before the half-hourly data arrives, you can still give the client a sensible budget figure. Base it on an assumed battery size and state what the price includes. Hold back the final kW, kWh, savings and payback until you can see when the site uses power and how long its peaks last.
What you can put in the first quote
You can include:
- an assumed battery and inverter size in kW and kWh
- the EMS controller, meter, CTs and standard commissioning
- survey, design and DNO application fees
- software, monitoring and support charges
- allowances for cabling, switchgear, groundworks and site access
Tell the client which prices are fixed and which may change after the survey. State what you have assumed about the switchboard, cable runs, battery location, fire requirements, internet connection and existing metering.
This gives the client enough information to decide whether the project is within budget. It also protects you from committing to a battery size before you have seen the site data.
Keep any DNO cost as an allowance until the network operator has reviewed the proposed battery power and export arrangement. Reinforcement work or a lower export limit could change the equipment and installation price.
What needs to wait for the half-hourly data
Do not put a firm number against:
- the final battery kW and usable kWh
- peak-shaving or tariff-shifting savings
- how much spare solar the battery can store
- expected battery cycling
- client-specific trading income
- payback or ROI
A yearly bill gives you the total kWh. It does not show the load shape.
Two sites might each use 500,000 kWh a year. One could have a 200 kW peak that lasts for half an hour. The other could hold that extra demand for three hours. They need different batteries, even though their annual consumption is the same.
The half-hourly data shows when the peaks happen, how high they reach and how long they last. It also shows how demand changes across working days, weekends and seasons.
You could put this in the proposal:
This budget price uses the assumed battery size and site details shown. We will confirm the final battery size, installed price, savings and payback after checking the site’s half-hourly data, completing the survey and receiving any required DNO costs.
That wording gives the client something they can take into an internal budget discussion. It also reduces the chance that you will need to explain later why the battery size, project price or payback changed once you get the site data.
How do we get and check the client's half-hourly data before final battery sizing?
Get at least 12 complete months of half-hourly data for every MPAN or MPRN the battery will serve. Before you size up anything, make sure the file covers the right meters, matches what the battery will see at the CT point, uses the right units and broadly lines up with the client’s bills.
How to get the right half-hourly data
Get the latest bill for each supply first. That gives you the MPAN in Great Britain or MPRN in Ireland, the meter serial number, supplier, account number and any separate import or export meters.
In most cases, the client can download the raw CSV or Excel file from their supplier portal. If you are getting it for them in Great Britain, the supplier or data collector will normally ask for a signed letter of authority. EDF, for example, asks for the account details, written permission and an authorised signature before it releases smart-meter data.
For an Irish site, ask the client to link the MPRN to an ESB Networks Online Account. They can then download half-hourly import and export data where it is available.
Ask them for:
- at least 12 complete months
- 24 months if they can get it
- separate import and export files
- anything showing whether readings are actual or estimated
- the site’s opening hours, shutdowns and operating calendar
One full year should pick up winter heating, summer cooling, holidays and production changes. A second year helps you spot whether the latest 12 months included an unusual closure, new shift or temporary drop in output.
What to check before you size the battery
First, make sure the file covers everything the battery will see. A site with several MPANs, tenant supplies or separate switchboards may need more than one file. Grid import can also hide part of the real site load where solar or an existing battery already supplies some of it.
Once you get the file, look for:
- missing or duplicate half-hours
- long runs of zero or repeated readings
- peaks that do not make sense
- estimated sections
- supplier or meter changes
- the wrong CT multiplier
- unclear kW or kWh units
A normal British settlement day has 48 half-hours. The spring clock-change day has 46 and the autumn one has 50, so do not treat those as faults (Elexon).
If the file gives kWh for each half-hour, multiply by two to get average kW. Leave it alone if the column already shows kW.
Add up the intervals for each billing period and compare the total with the billed kWh. If the numbers are well apart, find out why before you use the data.
Ask what they are planning to add to the site. New EV chargers, heat pumps, machinery, tenants, shifts or solar may mean you need to change the battery size.
Use the peak height to work out the battery kW. Use the peak length to work out usable kWh. If short machinery or charging spikes matter, half-hourly data may smooth them out. Fit temporary higher-resolution monitoring before you lock the inverter size.
Is a blended electricity rate enough to model commercial battery savings?
No. A blended rate is fine for a first-pass proposal, but it is too blunt for the final savings figure. It mixes cheap and expensive periods together, includes charges the battery may never reduce and tells you nothing about when the site imports power. Get the real tariff and half-hourly data before you quote savings or payback.
Why the blended rate can throw the proposal out
A blended rate usually comes from dividing the total electricity bill by the total kWh used. That can give you a quick budget figure, but it does not show which costs the battery can actually avoid.
A commercial bill may include:
- different day, night and peak rates
- standing charges
- capacity or maximum-demand charges
- DUoS and other pass-through charges
- export payments
- taxes and levies
Some of those costs may fall when the battery runs. Others stay on the bill whatever you do. Ofgem’s business energy guidance separates unit rates from standing charges for this reason.
The average rate can also hide the tariff spread you are trying to use. Say the client pays 12p per kWh overnight and 28p during a higher-rate period. With 90% round-trip efficiency, the battery needs about 1.11 kWh of overnight electricity to deliver 1 kWh later.
That charging electricity costs about 13.3p. Avoiding a 28p import leaves about 14.7p before you allow for battery wear, auxiliary power and software charges. Put the same 20p blended rate against both periods and the model misses that saving.
You can also go too far the other way. If you value every discharged kWh at the blended rate without taking off the charging cost, the proposal shows more savings than the battery can deliver.
What to use for the final figures
Use at least 12 months of half-hourly data and rebuild the client’s bill from the actual tariff.
You will normally need:
- each import rate and the times it applies
- standing, capacity and demand charges
- solar generation and the export rate
- battery power in kW and usable capacity in kWh
- charge and discharge efficiency
- minimum state of charge and any reserve
- site import and export limits
- battery degradation, controller and software costs
Start by running the historical load through the tariff without the battery. Compare the result with the client’s invoices. If the totals are well apart, check the tariff bands, meter data, pass-through charges and billing dates before you trust the model.
Then run the same half-hourly data with the battery included. Compare the two bills to see what the battery saves. Take off the controller, software and other running costs before you put the final figure into the proposal.
Use the blended rate to decide whether the job deserves a closer look. Do not use it for the final annual saving or payback.
GridVolt’s simulator uses the client’s actual tariff inputs, including time-of-use rates, DUoS charges and the export rate. This lets you model the battery against the bill the client really pays.
How do we find the commercial battery size that gives the best payback?
Run several real battery and inverter combinations through the same half-hourly model. Then compare what each option costs with the extra savings it produces each year. The best-payback size is usually the point where another cabinet or a larger PCS adds more to the price than it adds to the annual savings.
Size the battery kW and kWh separately
Start with the job the battery needs to do. Battery power in kW tells you how much site load it can cover at one time. Usable capacity in kWh tells you how long it can keep doing it.
If the site is 100 kW over the target import level for half an hour, the battery needs about 50 kWh of usable energy before you allow for losses and reserve. If the same 100 kW excess lasts three hours, it needs about 300 kWh. The discharge power is similar, but the second job needs far more stored energy.
Use the client’s half-hourly data rather than a standard business profile. Elexon says its published load profiles represent an average customer in each profile class, so they cannot show when this site peaks or how long it stays above the target.
For each size, check:
- how often the site goes over the target import level
- how long it stays there
- whether solar surplus or a cheaper tariff period can recharge the battery
- whether another peak arrives before the battery has recharged
- the site’s import and export limits
- how much battery capacity remains after reserve and losses
- whether the client plans to add EV chargers, machinery or extra shifts
Half-hourly data can smooth out short machinery or charger spikes. If those brief peaks will decide the PCS size, fit temporary higher-resolution monitoring before you lock it in.
Compare real packages and find where the extra spend stops paying back
Run combinations such as 100 kW/200 kWh, 100 kW/400 kWh and 200 kW/400 kWh through the same tariff and load model.
Use the full installed price for each option. Include:
- extra battery cabinets
- the PCS
- switchgear and cabling
- civils
- controls
- commissioning
Then compare the annual savings, simple payback and lifetime return for each package.
NREL’s REopt model follows the same broad method. It calculates battery power and capacity separately, then matches the result to a battery package that is actually available.
The larger option may save more money overall and still give a worse payback. That often happens when the site has too few long peaks, the battery cannot recharge between them or the extra capacity spends much of the year unused.
GridVolt’s simulator can compare real battery packages against the same half-hourly data, solar profile and tariff. You can then quote the package with the strongest payback and show the client exactly what they gain by paying for the next size up.
How do we choose between more battery power and more usable capacity on a commercial project?
Add more power when the battery cannot charge or discharge fast enough for the job. Add more usable capacity when it runs out before the peak or tariff window ends. The half-hourly data should tell you whether the site needs more kW, more kWh or a bit of both.
When the job needs more battery power
More kW helps where the site has short, high peaks or the battery must recharge inside a tight window.
Say the client wants to keep import below 300 kW, but the site reaches 380 kW for half an hour. The battery needs to discharge at about 80 kW during that period. A 40 kW PCS cannot cover the full peak, even if the battery has plenty of stored energy.
You may need more power if the battery has to:
- catch short peaks from machinery, refrigeration or EV chargers
- keep the site below an agreed import limit
- soak up a short burst of spare solar before it exports
- recharge during a short low-rate tariff period
- recover between two peaks on the same day
Check the charge side as well as the discharge side. A larger PCS will not help if the site only has 50 kW of spare import capacity overnight. You can hit the same problem if the DNO limit, export limit or solar inverter caps the power available.
Half-hourly data can smooth out brief peaks. If a charger bank or process load rises sharply for a few minutes, fit temporary higher-resolution monitoring before you lock in the PCS size.
When the job needs more usable capacity
More kWh helps where the battery has enough power but cannot keep discharging for long enough.
Using the same 300 kW import target, suppose the site stays at 340 kW for three hours. The battery only needs about 40 kW of discharge power, but it needs around 120 kWh of usable energy before you allow for losses and reserve.
You may need more capacity if the battery has to:
- cover a broad afternoon or evening peak
- store several hours of surplus solar
- shift load across a long expensive tariff period
- deal with repeated peaks before it can recharge
- keep energy back for backup or another agreed use
Work from the usable kWh, rather than the nameplate figure. Check how much remains after the minimum state of charge, client reserve, conversion losses and any capacity held back for trading or backup.
Then compare real packages and their full installed costs. More power may mean a larger PCS, switchgear, cables and connection work. More capacity may mean another cabinet, more space and extra civils.
GridVolt’s simulator can compare different PCS and battery combinations against the same half-hourly data, tariff and solar profile. Add kW until the battery can charge or discharge fast enough. Add kWh until it can keep doing the job for long enough. Stop when the next PCS or battery block costs more than the extra saving it produces.
Should we model solar and battery savings together in a commercial battery proposal?
Yes. Run the solar, site load and battery together through the same half-hourly model. Solar changes what the site imports and exports, and that changes what remains for the battery to do. Then split the figures in the proposal so the client can see the solar-only saving, what the battery adds and the total saving from the full project.
Why separate models can count the same saving twice
Solar changes the load the battery sees. During each half-hour, the PV may supply the site directly, charge the battery, export to the grid or be cut back because the site has reached its export limit.
The battery then works on what remains. It may store spare solar, discharge after generation drops or reduce a peak that solar alone cannot cover.
If you run solar and battery separately and add the two savings figures together, both calculations can end up claiming the same imported electricity or the same peak reduction.
Say the site would normally import 100 kWh during one period. The solar-only calculation may show that PV avoids 60 kWh. A separate battery calculation based on the original load may show another 50 kWh avoided. Add them together and you get 110 kWh, even though the site would only have imported 100 kWh.
Remember that spare solar already has a value if the client can export it. A kWh sent into the battery is not free if the client could have sold it. Ofgem confirms that SEG payments depend on metered exports and that suppliers set their own rates and contract terms.
What to show in the proposal
Run the same half-hourly load, tariff and solar figures through at least three cases:
- the existing bill with no new equipment
- solar only
- solar and battery together
Add a battery-only case if the client is seriously considering that option.
Show the results as:
- Solar-only saving: Existing bill minus solar-only bill
- Battery’s added saving: Solar-only bill minus combined bill
- Total project saving: Existing bill minus combined bill
Also show where the solar and battery energy goes:
- solar used directly on site
- solar sent into the battery
- grid electricity used to charge the battery
- battery discharge supplied to the site
- exported and curtailed solar
- the highest grid import
- the client’s actual export rate
- any battery reserve kept for backup, trading or another agreed use
Only include shared switchgear, cabling, civils, controls and commissioning once in the combined project cost.
NREL’s solar-plus-storage modelling treats solar and storage together because battery charging and discharging change how much solar the site uses, stores or exports in each period.
GridVolt’s simulator runs the solar array, half-hourly site load, tariff, export rate and battery together. That lets you show the client exactly how much extra the battery adds to the solar proposal.
What export price should we use in a commercial solar-and-battery model if the client has no export contract yet?
For a GB job with no export contract, use 3p/kWh as a cautious working figure and show the client what happens at 0p/kWh as well. Once they get a written offer from an export supplier, swap that rate into the model. For an Irish job, get a current supplier rate rather than using the GB figure.
Do not lift the best advertised rate into the proposal
There is no single SEG rate that every commercial client can get. Each supplier sets its own price, contract length and conditions.
At 16 June 2026, published business examples include:
- Octopus at 3p/kWh through its basic business SEG route
- E.ON Next at 6p/kWh on its variable export tariff
- E.ON Next at 8.5p/kWh on its fixed business tariff
- Octopus Panel Power at 12p/kWh
The higher rates usually come with extra conditions. These may cover the size of the solar array, the export meter or who supplies the client’s imported electricity.
Octopus Panel Power, for example, only covers qualifying systems below 150 kWp where the business also buys its electricity from Octopus.
If you put 8.5p or 12p into the proposal before checking those rules, the payback may depend on a tariff the client cannot actually get.
Also check what happens when the battery exports. If it can charge from the grid, do not assume the supplier will pay the same rate for every kWh that leaves the site. Ask the supplier to confirm whether the tariff covers direct solar export, battery export or both.
Show the client a cautious case and the contracted case
Run three versions:
- 0p/kWh
- 3p/kWh
- the supplier’s written rate once the client has it
Only count electricity that actually reaches the export meter. Take off anything the site uses directly, sends into the battery or loses because the G100 limit forces the solar to turn down.
A 500 kW array will not earn export income on every spare kWh if the connection offer only allows the site to export 100 kW.
Keep a note of:
- the export rate and the date you checked it
- whether it is fixed or variable
- any limit on system size
- the export MPAN and meter setup
- whether the client must use the same supplier for import
- whether battery export qualifies
- the contract length and any fees
For an Irish job, ask the client’s supplier for the current export rate before you lock the figures.
GridVolt’s simulator keeps the export price as a separate figure. You can show the 0p case, the cautious working case and the contracted case without changing the solar or battery assumptions.
How do we account for a G100 export limit when modelling savings for a commercial solar-and-battery project?
Start with the export limit in the DNO offer. That is the most the site can send back to the grid at any one time, whether the power comes from the solar, the battery or both. If the site cannot use or store the rest, the solar has to be turned down, so do not include that energy in the savings or export income.
Work from what leaves the site
Use the export figure in the DNO connection offer or agreement. Do not take it from the solar inverter rating or battery PCS size.
The G100 scheme looks at the power leaving the whole site at the connection point. For each half-hour, work out:
Net export = solar generation + battery discharge − site demand − battery charging
If that figure goes over the DNO limit, something has to change. The battery can reduce its export, charge from the spare solar, the solar inverters can turn down or another load can use the power.
Say the site has:
- 500 kW of solar generation
- 220 kW of site demand
- a 100 kW export limit
- a battery that can charge at 150 kW
Without the battery, the site uses 220 kW, exports 100 kW and loses 180 kW because the solar has to turn down.
With the battery charging at 150 kW, the site still exports 100 kW, but only 30 kW needs to be cut back.
That only works while the battery has room and can charge fast enough. If it is full, charging too slowly or keeping room back for another job, more solar will still be lost.
The battery shares the same export limit. If the solar is already sending out 80 kW under a 100 kW limit, the battery can only add another 20 kW at that point.
EREC G100 sets the technical rules for customer export and import limitation schemes.
Show how much spare solar the battery saves
Run at least three cases through the proposal:
- the site as it is now
- solar only with the G100 limit applied
- solar and battery with the same limit applied
For each case, show:
- solar used directly on site
- solar sent into the battery
- electricity exported
- solar that had to be turned down
If the battery stores solar that would otherwise have been lost, that electricity had no export income attached to it. If the battery stores solar the client could have sold, take that lost export payment off the saving the battery produces later.
Half-hourly data is fine for the main financial model, but it can smooth over shorter export peaks. If the solar array is large compared with the site load or export limit, use 5-minute or 15-minute data where you can get it. If you only have half-hourly data, allow for more solar being turned down than the model first shows.
GridVolt’s simulator can apply the DNO export limit across the solar-and-battery model and show how much spare solar the battery captures. Only count the money those units save or earn later, after battery losses and any export income the client gave up.
Which assumptions will a finance director challenge first in a commercial battery proposal?
A finance director will usually go straight to the annual saving. They will want to know where the number came from, which parts of the bill the battery actually cuts and how much depends on export or trading income that is still only an assumption. After that, they will look at the full project cost and what happens if the job performs below plan.
Where they will test the saving
Expect finance to start with the payback and work backwards.
They may ask:
- Which MPANs and months does the model cover?
- Does the model come close to the bills the client actually paid?
- Which tariff charges will the battery really reduce?
- Have you counted the same solar or battery saving twice?
- Does the export rate come from a written supplier offer?
- Is trading income shown before or after fees?
- Does the model use usable capacity or the battery’s nameplate figure?
Use the client’s actual tariff, invoices and checked half-hourly data. A blended rate can hide standing charges, different time bands and costs the battery will never reduce. Ofgem’s business energy guidance separates the unit rate from standing charges, so make sure the saving links back to the bill lines you have used.
Keep bill savings, export income and trading income on separate lines. P415 gives eligible batteries a route into the GB wholesale market through a Virtual Trading Party. It does not tell you how often the battery will trade or what it will earn.
Finance will normally want to see the result with no trading income as well. If the project only works with trading included, make that obvious in the proposal.
What they will expect to see in the price
The battery and PCS are only part of the installed price.
Include the:
- PCS or inverter
- controller, meter and CTs
- switchgear and cabling
- civils and enclosure work
- fire and ventilation measures
- DNO and professional fees
- commissioning
- annual software, maintenance and trading charges
If the DNO, civils or switchgear cost is still an allowance, label it as an allowance. Do not present it as a fixed price.
Finance may also ask whether the battery can keep producing the same saving after several years. Show the usable kWh, efficiency, reserve, warranty limits and expected capacity loss. Do not repeat the first-year saving across the full payback period if the battery will have less usable capacity later.
Payback will usually be the first number they check. They may then ask for NPV, IRR and year-by-year cash flow using their own discount rate. Be ready to rerun the figures if:
- a smaller tariff spread
- less peak reduction
- no trading income
- a higher installation cost
- a later commissioning date
GridVolt’s simulator can show bill savings, optimisation gains and trading income separately, then run the figures again under a downside case. Before you send the proposal, make sure every important number comes from the client’s meter data, tariff, supplier quote, battery warranty or agreed contract terms.
How do we stop a commercial battery model double-counting self-consumption, peak savings and trading?
Put self-consumption, peak shaving and trading through the same half-hourly battery schedule. The battery only has one state of charge, one PCS limit and one amount of usable energy. If it uses power or stored energy for one job, that power and energy may no longer be available for another.
Track where the battery energy goes
For every half-hour, record:
- solar used to charge the battery
- grid electricity used to charge it
- battery discharge into the site
- battery discharge to the grid
- site import and export
- state of charge
- battery losses
- any capacity kept back for trading, backup or peak shaving
Every discharged kWh needs one destination. It either supplies the site or leaves through the export meter.
Say the battery discharges 100 kWh during one period. If 80 kWh supplies the building and 20 kWh exports, give the 80 kWh the avoided-import saving. Give the 20 kWh the export or trading payment. Avoid valuing the full 100 kWh both ways.
You also need to carry the state of charge into the next half-hour. If the battery trades earlier in the day, it may have less energy left when the site reaches its afternoon peak.
NREL’s behind-the-meter battery research shows that tariff shifting and peak reduction compete for the same battery capacity. The controller therefore needs to choose between them as the day unfolds.
Make every saving add back to one total
Start with the site or solar-only bill. Then add the battery uses one at a time:
- Self-consumption and tariff shifting
- Peak-charge reduction
- Contracted trading
Compare the result after each step. This shows what each use adds without claiming the same battery action twice.
Use the client’s real bill and contracts:
- recalculate the import charges after the battery runs
- recalculate any maximum-demand or capacity charge from the new site peak
- use trading payments from the measured volumes or availability in the agreement
- include grid charging, battery losses and solar export income given up
- take off aggregator fees, revenue share and recovery charging
One battery discharge may reduce both the imported kWh and a separately billed kW peak. That is a genuine saving on two different bill lines. The problem starts when you use a blended rate that already includes the peak cost and then add the peak saving again.
GridVolt can run site savings and trading through the same battery schedule. Before you put the figures into the proposal, check that the separate saving lines add back to the combined annual result.
Where should we draw the line between a free commercial battery estimate and paid feasibility work?
Keep the first estimate free while you are working out whether the job is worth taking further. Start charging when the client wants you to check the half-hourly data properly, choose a battery size for that site, inspect the electrical setup or give them figures they can use to approve the spend, raise finance or get firm prices.
What belongs in the free estimate
The free estimate should help you qualify the job without giving away days of modelling and design work.
You can usually produce it from:
- recent electricity bills
- annual electricity use
- recorded maximum demand
- the current tariff
- existing or proposed solar capacity
- basic operating hours
- known import and export limits
From that, you can give the client a rough battery kW and kWh range, an early installed price and a likely savings or payback range.
Tell them what you have and have not checked. At this stage, you may not have reviewed the half-hourly data, matched the model back to the bills, looked at the switchgear or confirmed the DNO position.
The free estimate should answer one question. Does the job look good enough to spend more time on?
It should not promise a final battery size or annual saving. Ofgem’s work on half-hourly settlement shows why timing matters for batteries and time-of-use tariffs. A bill-based estimate cannot show when the site peaks, how long those peaks last or whether the battery can recharge before the next one.
When to start charging for the work
Move into paid feasibility when the client wants an answer based on their site rather than a set of early assumptions.
That normally means:
- checking the half-hourly file and matching it back to the bills
- putting the client’s actual tariff into the model
- comparing real battery and PCS combinations
- separating solar, peak, tariff and trading savings
- visiting the site
- checking switchgear, CT positions and connection points
- reviewing G99 or G100 requirements
- obtaining firm supplier and installation prices
- producing NPV, IRR, cash flow or downside figures
- writing a report for directors, lenders or procurement
That work takes real engineering and modelling time. Once you start checking the electrical design or giving the client figures they will rely on, it has gone beyond a free sales estimate. HSE also places duties on battery designers and installers throughout the system’s life.
Agree what you will check, what the client will receive and what you will charge before you start. You can credit some or all of the feasibility fee against the installation contract if the client goes ahead.
GridVolt’s free simulator can help you produce an early battery-plus-solar estimate without buying separate modelling software. The paid work starts when you need to check the data, confirm the tariff, compare real equipment or give the client figures they can use to sign off the project.
How do we prove the commercial battery savings after installation?
Agree with the client how you will measure the savings before the battery goes in. Use the site meter and battery meter to work out what the site would have imported or exported without the battery each half-hour. Compare that with what actually happened, then show trading income and extra running costs separately.
Make sure the meters tell the same story
The supplier bill only shows what crossed the grid meter. It does not show what the site would have used without the battery.
You therefore need readings from:
- the grid connection meter
- the battery’s AC meter
- the solar system where it affects battery charging
- the power the controller asked for and what the battery delivered
- the battery state of charge
- battery faults and downtime
Check the CT direction, ratio, phases and import or export signs during commissioning. Make sure all the meters use the same clock and half-hour periods.
Run a controlled charge and discharge test before handover. If the battery discharges at 40 kW, the site import should fall by roughly 40 kW after you allow for any change in the site load or solar output. That test should pick up reversed CTs, wrong multipliers and clocks that do not match.
Record the battery state of charge at the start and end of each reporting period as well. If it finishes the month emptier than it started, some of the apparent saving came from energy already stored in the battery.
Work out what the bill would have been without the battery
For every half-hour, add back the electricity the battery discharged and take off the electricity used to charge it.
Using import as a positive figure:
No-battery grid position = actual grid position + battery discharge − battery charging
If the site imports 120 kW while the battery supplies 40 kW, it would have imported 160 kW without the battery.
If it imports 180 kW while the battery charges at 50 kW, the site load without that charging was 130 kW.
Put the client’s real tariff against both sets of figures. Include the import rates, export payments and any peak, capacity or network charges the battery can actually change.
Show the client:
- the saving on their electricity bill
- net trading or flexibility income
- software, aggregator and extra maintenance costs
- the total benefit after those costs
Use the aggregator’s settlement statement for trading income. Avoid estimating it from the amount the battery discharged.
Also ask whether anything changed on site during the month. New machinery, extra shifts or longer opening hours can change what the site would have used without the battery.
GridVolt’s controller records site and battery data that can help with this check. Before you use the savings in a contract or performance claim, make sure the client can see the raw half-hourly data, tariff used and calculation behind the figure.
Check whether the numbers in your commercial battery proposal stand up
Before you put the proposal in front of the client, GridVolt can help you test the battery size, annual saving and payback against the site’s actual load, tariff, solar output and export limits.
To review the project, send us:
- the proposed battery and inverter make, model, kW and usable kWh
- at least 12 months of half-hourly or quarter-hourly electricity data
- recent electricity bills and the current tariff
- the solar generation profile, where solar forms part of the project
- the proposed export rate or supplier offer
- the site’s agreed import and export limits
- the estimated installed cost, including switchgear, cabling, civils and commissioning
- annual controller, software, maintenance and trading charges
- details of any planned EV chargers, heat pumps, machinery or extra shifts
GridVolt’s simulator can compare different battery and PCS sizes against the same site data. It can also show:
- whether the blended rate hides important tariff differences
- how much of the saving comes from solar self-consumption, tariff shifting or peak reduction
- what the battery adds above the solar-only case
- how a G100 limit changes export and curtailment
- what happens if the client earns no trading income
- whether the next battery cabinet adds enough saving to justify the extra cost
This gives you the figures behind the proposal before the client asks where the saving came from, whether the battery can deliver it and what happens if the main assumptions change.
Get in touch by filling out the form on this page or through our contact page.