The forecasted carbon levels provided as part of the Green Meter are based on our best guess of future electricity supply emissions using recent historical emissions data.

We’re fairly confident in our predictions, but even the best forecasts are subject to change! So we can’t make any promises that things will pan out exactly the way we predicted.

We plan to keep improving our forecast accuracy as we get more data.

Past carbon levels in the Carbon Insights graph marked as ‘actual data’ are based on data from Transpower’s EM6 website. EM6 enables monitoring of New Zealand’s historical energy emissions in near-to real time.

We forecast carbon emission levels up to 3 days in advance, to help you plan your discretionary electricity usage. These forecasts are based primarily on historical energy emissions data from Transpower.

We update the future forecasts as new information becomes available, so if you visit the Green Meter again later in the day you might notice that the forecast has changed slightly.

We’re fairly confident in our forecasts, but just like the weather, the Green Meter forecasts are subject to change! So we can’t make any promises that things will pan out exactly the way we predicted.

On average, our forecasted energy emissions data predicts the actual emission level for each half hour period to a variation of ~18% (based on 2022 data, as forecasted at 24 hours ahead of time. Within 24 hours the forecast tends to get even more accurate).

That means that our forecasts typically turn out to be within ~18% above or below the actual emission level.

The power grid refers to the energy infrastructure made up of poles and wires, used to transmit electricity from generation plants to your homes and businesses.

When we talk about the ‘greenness of the grid’ we’re referring to the emissions intensity of the combined countrywide electricity generation sources (forecasted or actual) at any given time.

Here in Aotearoa New Zealand we’re lucky to have a predominantly ‘green’ power grid, with most of our electricity generation coming from renewable sources such as hydro, geothermal and wind. But we still rely on fossil fuels to help fill the gaps - and that’s where the Green Meter comes in handy.

Carbon emissions are measured in tonnes of carbon dioxide (CO₂*). In the Green Meter, CO₂/half hour refers to the forecasted amount of carbon dioxide emissions released per half hour as a result of New Zealand’s countrywide electricity generation.

We record CO₂ forecasts and actuals in half hour increments.

*To get super technical on it, the unit is actually CO₂-e, which stands for CO₂ equivalent’. CO₂ equivalent is the amount of CO₂ produced, plus any other greenhouse gases produced, like nitrous oxide and methane, whose impact has been converted into the amount of CO₂ it would take to have the same impact.

You read the Green Meter much like a Fire Danger sign. Whichever level the arrow is pointing to reflects the most up-to-date current carbon forecast of the power grid. You can find the forecasted tonnes of CO₂ per half hour just below the meter, next to the ‘Current forecast’ status.

A reading of ‘Worsest’ indicates that, based on historical trends, we forecast more carbon emissions than usual being produced as a result of nationwide electricity generation sources.

A reading of ‘Betterest’ indicates that, based on historical trends, we forecast less carbon emissions than usual being produced as a result of nationwide electricity generation.

A reading of ‘Goodish’ indicates that, based on historical trends, the forecast carbon emissions being produced are pretty average.

The Green Meter forecast levels change due to predicted changes in the nationwide electricity generation sources (e.g. hydro, geothermal, wind, gas, coal). Electricity generation sources change due to many factors, including weather and consumer demand for power.

For example, hydro provides the majority of New Zealand’s power generation supply. If we haven’t had much rain lately and the lakes are running low, the power grid might need to call upon more gas generation to keep up with the demand for electricity.

Another example is during morning and evening peaks. Through the day, renewable sources like hydro might be able to supply most of the power the grid needs. But when everybody gets home from work, turns on the lights and starts cooking dinner or doing the washing at the same time, it creates a big spike in demand for power. And hydro might not be able to keep up, so once again, the grid might need to call upon fossil fuel generation to help meet the demand.

Thanks to the increased demand during mornings and evenings, you’ll usually see forecasted carbon emissions looking worse during these times. Whereas in the middle of the night when most people aren’t using much electricity, you’ll typically see that forecasted carbon emissions look better.

We update the carbon level thresholds from time to time to account for changes such as seasonal variability and changes in generation sources over time. That’s because sometimes whole seasons have a higher or lower average emission level, due to extreme weather or increased electricity demand.

For example, people tend to use more electricity when it’s cold, meaning it’s more likely that we need to lean on fossil fuels to meet electricity demand during winter. This might cause the average emissions of the whole winter season to be higher.

On the flip side, as we see increased investment in renewable energy, it’s likely that we’ll start to see average carbon emissions of the grid declining over time.

If we didn’t periodically update the Green Meter level thresholds to account for these trends, you might start to see day after day with forecasts of ‘worsest’ or ‘betterest’!

Updates to the thresholds won’t impact the levels of any historical data shown in the Carbon Insights graph, but we’ll clearly indicate on the graph when the level thresholds have been updated.

In general, Betterest means we’ve forecast that more renewable energy and less fossil fuels are being used to generate electricity. This lower forecasted carbon emissions as a result of your electricity usage during these times. We think lower emissions are better, and hopefully you do too!

Worsest means we’ve forecast that more fossil fuels are being used and more forecasted carbon emissions are being produced as a result of your electricity usage during these times.

In the Carbon Insights graph you’ll notice some half hour time periods are labelled ‘actual data’ while others are labelled ‘forecast’.

Forecast data are predicted carbon emission levels based on historical energy emissions. Any half hour periods in the future will be marked as a ‘forecast’.

Actual Data is confirmed carbon emission levels based on actual historical generation sources and associated emissions data, based on data from Transpower’s EM6 website. The half hour periods on the Carbon Insights graph will always be marked as ‘forecasts’ until we get the most up-to-date data from Transpower, typically about 30 minutes - 2 hours after they occur.

In the Daily view of the Carbon Insights graph, you can see the CO2 emissions per half hour of each 24-hour period. Past actual data is shown, plus 3 days of forecasted data. You can swipe left and right to see previous/future days. Each 24-hour period is separated by a vertical dotted line.

In the Weekly and Monthly view you can see the average CO2 emissions per half hour over the specified timeframe. These averages are based on actual data only (forecasted data is not included in the Weekly and Monthly views). For example, in the Weekly view with 10:30am - 11:00am highlighted, you are viewing a 7-day average of actual CO2 emissions during the 10:30am-11:00am time period. You can swipe right to see the average half-hourly levels from previous weeks and months. Each week/month timeframe is separated by a vertical dotted line.