Answers & Explainers
Straight answers to common questions about battery storage, energy trading and energy management — written by the GridVolt team.
When a separate energy management system can improve battery performance, and when the inverter’s existing controls are already enough.
Often, yes. You can usually keep the battery and inverter if the inverter can share the live data the EMS needs and accept charge and discharge instructions from it. The EMS supplier should check the exact model and firmware first, then test the controls, metering and what happens if communications fail.
Read full answerNot always. If the inverter already follows the right tariff times, stores spare solar, controls peaks and keeps the needed reserve, another EMS may add little. A separate EMS makes more sense when the site changes through the day and the battery needs its schedule updated using live data and forecasts.
Read full answerThere is no standard percentage. Extra savings depend on the site’s electricity use, tariff, solar output, battery size and how well the inverter already controls the battery. Compare the same battery under fixed schedules and optimisation software, then use the extra annual saving after all EMS costs as the client figure.
Read full answerA built-in schedule can be enough when the site uses electricity in a steady pattern, tariff prices change at set times and solar output is fairly predictable. If the battery can charge, discharge and keep its reserve at the right times without regular changes, a separate EMS may not save enough extra money to pay for itself.
Read full answerAdd a separate EMS when it can save or earn more money than it costs to run. Compare the same battery using the inverter’s best controls and the separate EMS, using the same site data, tariff and battery settings. The extra saving after controller, software, support and other EMS costs is the figure that matters.
Read full answerPractical guidance on half-hourly data, battery sizing, savings models and building commercial battery proposals clients can trust.
Use a blended rate only for a rough first look, not the final proposal. It hides when electricity is cheap or expensive and can mix charges the battery can reduce with charges it cannot. For the client figures, use the real tariff and half-hourly load so you can show where the saving comes from.
Read full answerYou need half-hourly data for a final battery size, annual saving and payback. You can still give a budget quote before it arrives, using clear assumptions and provisional costs. Then update the battery size and financial figures once you have modelled the client’s actual half-hourly load.
Read full answerAdd more kW when the battery cannot charge or discharge fast enough. Add more usable kWh when it can deliver enough power but runs out too soon. Check short site peaks as well as half-hourly averages, then compare the real battery and PCS packages to see where extra size stops improving the client’s return.
Read full answerAsk for about 12 months of half-hourly data for every meter the battery will serve, plus recent bills. Check that the file covers the right meters, has no major gaps or strange readings and clearly shows whether values are kW or kWh. Also ask about future loads such as EV chargers or new machinery.
Read full answerAgree the savings method before handover. Use the site’s real half-hourly import and export plus the battery’s charging and discharging data to estimate what the bill would have been without the battery. Apply the real tariff to both cases, then show bill savings, trading income and extra running costs separately.
Read full answerSize the battery around what the site needs it to do. Use kW to cover how high the peaks are and usable kWh to cover how long they last. Then compare real battery and PCS options, their full installed costs and the savings they produce, and choose the option that best meets the client’s payback, IRR or NPV goal.
Read full answerUse one half-hourly battery schedule for all savings. Each kWh can only do one job at a time, so electricity used to cut site imports cannot also be counted as export or trading income in the same period. Make the separate savings lines add back to one clear annual total.
Read full answerUse the export limit in the DNO agreement, not the size of the solar inverter or battery PCS. The site cannot export more than that limit, whether the power comes from solar, the battery or both. Model any solar that must be turned down and any spare solar the battery can store because of that limit.
Read full answerYes. Model the site load, solar and battery together in the same half-hourly model because solar changes what is left for the battery to do. Then show the client the solar-only saving, the extra saving added by the battery and the total project saving, without counting the same electricity twice.
Read full answerFor a GB job with no export contract yet, use 6p/kWh as a cautious working figure and also show a 0p/kWh downside case. Replace that estimate with the supplier’s written rate when the client gets one. For Ireland, get a current supplier rate instead of using the GB figure.
Read full answerA finance director will usually check the annual saving and payback first. Be ready to show the actual bills, tariff and half-hourly data behind the figures, where each saving comes from, the full project cost and what happens if savings or trading income are lower than expected.
Read full answerKeep the first estimate free when you are only checking whether the site looks worth pursuing. Start charging when the client wants site-specific work such as checking half-hourly data, choosing the battery size, inspecting the electrical setup or producing figures they can use for approval, finance or comparing bids.
Read full answerWhat to check when connecting an EMS to commercial batteries, including compatibility, metering, commissioning, warranties and fallback control.
Yes, if the battery maker allows outside control and the EMS stays inside the warranty rules. Check limits for charge and discharge power, state of charge, temperature, cycling and total energy used over the battery’s life. Being inside the battery’s safety limits does not automatically mean you are inside its warranty.
Read full answerYes. Set a minimum battery reserve so normal optimisation and trading cannot use it. If several minimum limits apply, use the highest one, such as the maker’s minimum charge, the client’s backup reserve or energy promised to another service. The local inverter or controller should still protect that reserve if the internet goes down.
Read full answerGet the exact battery, inverter, controller and firmware details and ask the EMS supplier to check them. The EMS must be able to read the right live data and send charge and discharge commands back to the inverter. A Modbus port or matching brand name alone does not prove it will work.
Read full answerMeasure net import and export where the whole site connects to the grid, not just at the battery inverter. If the inverter already receives accurate whole-site meter readings, the EMS may be able to use them. If not, it may need a direct meter connection or its own CT clamps.
Read full answerA third-party EMS needs to read key battery and site data, such as state of charge, available power, faults and whole-site import and export. It also needs limited permission to tell the inverter how much to charge or discharge. The battery, inverter and protection system must still control safety and grid limits.
Read full answerA third-party EMS normally needs an on-site controller, power, a connection to the inverter, whole-site meter readings and internet access. Some sites can reuse their existing meter, CT clamps and network. Others may need extra metering, cabling, a gateway, network equipment or a mobile-data connection before the EMS can work properly.
Read full answerThe battery should keep a safe local plan if the internet goes down. If the on-site controller can still talk to the meter and inverter, it may keep following its saved schedule. If that local link also fails, the inverter should move to an agreed fallback setting after a set timeout.
Read full answerThe installer or electrical contractor usually fits and wires the controller. The EMS supplier normally sets up the software and leads commissioning, while the battery or inverter maker handles faults inside its own equipment. After handover, the contract should clearly say who deals with each type of fault.
Read full answerHow commercial battery trading works, which sites can take part and how to calculate and present potential trading revenue to clients.
No. Peak shaving, backup reserve, protected loads and other agreed site needs must come before trading. Record how much battery power and energy the site needs to keep, when those rules apply and who can pause trading. The trading software should only use what is left after those limits are protected.
Read full answerNot through the same GridTrade route used in Great Britain. For an Irish project, base the main case on Energy Manager savings from tariff control, solar use and site-load management. Only add Irish market or flexibility revenue after GridVolt has checked the site and confirmed a suitable route and site-specific figure.
Read full answerNo. Since P415, an eligible GB commercial battery can use a qualified trading provider without the client changing electricity supplier. The normal supply contract stays in place while the trading service is handled separately. You still need to check the meter, battery controls, site limits and trading setup before promising income.
Read full answerYes, battery trading can still add income on a wholesale-linked tariff, but the two uses can overlap. The battery may already be charging in cheap periods and discharging in expensive ones to cut the bill. Ask GridVolt to check whether GridTrade adds extra value before putting any trading figure in the proposal.
Read full answerAfter commissioning, the clearest recurring revenue is a paid monitoring and maintenance service. Define exactly what you will check, how often you will report, which faults you handle, response times, site visits and what costs extra. Keep future upgrades or extra project work outside that service unless you have priced them in.
Read full answerChoose more inverter or PCS power when the battery needs to charge or discharge faster. Choose more usable battery capacity when it needs to keep going for longer. Check the site’s biggest power need, how long it lasts, the connection limits and the extra saving or trading income before paying for more kW or kWh.
Read full answerGridVolt forecasts what the site’s half-hourly meter would have shown if no trading instruction had been sent. That forecast is the baseline. After a trade, GridVolt compares it with the actual meter reading, and the difference can be the traded amount when the change came from the trading instruction.
Read full answerThere is no fixed GB minimum battery size for trading under P415. Some providers use 100 kWh as a first filter, but what matters more is how much spare battery power, usable energy and import or export headroom the site has after its own needs are covered. Smaller batteries can still be worth checking.
Read full answerDo not assume a quoted trading figure is what the client will receive. Ask whether it is gross market revenue or the amount left after charging costs, losses, provider fees, revenue share and other deductions. In the proposal, show the gross figure, each deduction and the expected customer payment separately.
Read full answerSend GridVolt the battery and inverter details, about 12 months of half-hourly import and export data, the site’s connection limits, tariff and any battery capacity needed for peak shaving, backup or solar. GridVolt uses this to work out what power and stored energy are really left for trading.
Read full answerA commercial battery can make several thousand pounds a year or more from trading, but there is no safe standard figure for every site. The result depends on spare inverter power, usable battery energy, site demand, meter setup, connection limits, prices and fees. Get a site-specific forecast before promising a number.
Read full answerIt depends on what caused the missed trade and what the contracts say. GridVolt can investigate using trading, controller, battery, communications and meter records where available. Before handover, make sure the client knows who supports each part of the system and who to contact if a trade is missed.
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