VPP Calculator — How Much Could Your Home Battery Earn?

What Is a Virtual Power Plant?

A Virtual Power Plant (VPP) is a network of home batteries — and sometimes electric vehicles — coordinated by software to act as one large power source. Instead of a single gas or coal plant, a VPP draws on thousands of small batteries in homes and businesses. When the grid needs power during peak demand, the VPP signals those batteries to discharge. When there's cheap or surplus renewable energy, they charge up.

For you as a battery owner, joining a VPP means your battery buys electricity when it's cheap — overnight on a low-tariff window, or during midday when solar is flooding the grid and prices crash — and sells it back when it's expensive, during the morning and evening peaks. That spread is where VPP earnings come from.

How Does Battery Arbitrage Work?

The daily cycle works like this: your battery charges during the cheapest hours (often overnight, or midday when grid solar supply pushes wholesale prices down). Then, during the most expensive hours — typically 5pm–9pm — the battery either powers your home so you avoid buying at peak retail rates, or exports surplus energy to the grid and earns a feed-in credit. VPP programs automate this: their software monitors real-time wholesale prices and makes the charge/discharge decisions for you.

Who Offers VPP Programs?

Australia: Amber Electric, Tesla Energy Plan, ShineHub, and Reposit Power. UK: Octopus Energy (Kraken Flex), Tesla Powerwall VPP, and Social Energy. US: Tesla Virtual Power Plant (California, Texas), Sunrun, and various utility demand-response programs. South Africa: Several providers are emerging as loadshedding drives battery adoption — Eskom's demand-response pilots and private aggregators like Rubicon and GridCars are building VPP capabilities. Most programs require a compatible battery — Tesla Powerwall, BYD, Enphase, and others are commonly supported.

Solar + VPP: The Best Combination

If you already have solar panels, a VPP becomes significantly more profitable — because your battery can charge completely for free during the day rather than buying overnight grid power. Here's why that matters:

• Midday solar surplus is free energy. A typical residential solar system (5–8 kW) can generate 20–35 kWh on a sunny day, depending on your location and climate. With a 10 kWh battery, the battery fills completely from solar during the middle of the day, at zero cost.
• Then it sells at peak wholesale prices. Once full, the battery waits for the evening price spike — typically 5pm–8pm when demand surges and wholesale rates can jump to 10–20× their midday lows. The battery exports, and you earn the high rate.
• Pure arbitrage profit. Because the charge cost was zero (solar), every cent earned from evening exports is pure revenue. Compare this to buying overnight grid power and selling at peak — you still earn the spread, but you've already paid for the energy.

In the VPP calculator above, set your solar system size and see how the "Solar → battery" flow drives the schedule. With enough solar to fill the battery daily, you may need zero grid charging hours — just free solar charge and profitable evening discharge.

What About Cloudy Days?

On low-solar days, a good VPP program will switch strategy: charge the battery from the grid during the cheapest overnight hours, then discharge at peak. You still earn the price spread — it's just smaller because you've paid for the grid energy. Many programs handle this automatically, switching between solar-priority and overnight-charge strategies depending on the forecast.

The Duck Curve — Why Solar Creates VPP Opportunity Worldwide

In markets with high rooftop solar penetration, wholesale electricity prices follow a "duck curve": they dip near-zero or even negative during midday when solar generation floods the grid, then spike sharply in the evening as solar fades and demand peaks. This pattern is now well-established in Australia (SA, VIC, QLD), California, parts of Germany, and increasingly in the UK and South Africa as solar capacity grows.

The duck curve is the core economic engine behind VPP: your battery charges when the grid is oversupplied and prices crash (midday in sunny markets, overnight in wind-heavy markets like northern Europe), then discharges when supply is tight and prices spike. The steeper the duck curve, the bigger the arbitrage spread — and the more a VPP battery earns.

VPP vs V2G — What's the Difference?

VPP (home battery) is designed for daily cycling: charge cheap, discharge expensive, repeat every day. Your 10 kWh battery might cycle 300–365 times a year. V2G (Vehicle-to-Grid) uses your EV battery for less frequent, higher-value events — a handful of wholesale price spikes per month worth potentially hundreds of dollars each. Both can earn you money and support grid stability; they target different assets and different price patterns.

The ideal setup is all three working together: rooftop solar charges both the home battery and the EV for free during the day; the home battery does daily VPP arbitrage; the EV does occasional V2G during extreme price spikes. Try our V2G calculator and EV Charging calculator to model those scenarios.

Frequently Asked Questions