What is a high matching score?

Hourly Matching in Practice series

This blog post is part of our Hourly Matching in Practice series, which aims to help newcomers to this topic quickly get up to speed ahead of the changes to the GHG Protocol's scope 2 emissions guidance.

Part 1: What is hourly matching and what does it mean for your business?

Part 2: What is a good matching score? (you are here)

Part 3: How can hourly matching work without hourly certificates?

Part 4: How and why are businesses getting started with hourly matching

How do you assess your matching score?

In our previous post, we explored what hourly matching is and what it means for your business. We learned that hourly matching means ensuring your renewable energy purchases align with your actual electricity consumption on an hour-by-hour basis, rather than just balancing the books annually. While it may sound scary, in practice, balancing your green energy books on an hourly basis instead of an annual one simply means that a couple of new numbers will be appearing on your energy bills, most notably your hourly matching score.

On an annual basis, it would be typical for all businesses on a green energy tariff to receive the same 100% matching score. (In fact, this is usually taken for granted, so much so that this “annual matching score” is often not reported at all). However, in a world of more granular matching, your matching scores are going to see a lot more variation, both within the year and between different businesses. You can now see scores from anywhere between 0 and 100%. This begs the question: what constitutes a “high” matching score?

In practice, the answer to this simple question is … it depends! In the past years, Granular Energy has helped manage a diverse set of clean energy products and, therefore, gained a good sense of what matching scores you can expect to achieve as an energy consumer in various scenarios. As hourly matching takes off in new markets (Hello Japan!) and is part of the proposed revisions to Scope 2 of the GHG Protocol, we are happy to share our knowledge and prepare you for upcoming changes. In this post, we will cover the key factors that influence matching scores and provide you with some simple benchmarks to assess how your business is doing.

What factors can affect whether your matching score is considered high or not?

Your matching score doesn't exist in a vacuum. Several interconnected factors determine whether a given score represents strong performance or point to opportunities for improvement. The main factors are:

• The temporal granularity of the matching score
• The technologies used to match your demand
• The diversity of technologies used
• The shape of your own demand and how well it aligns with clean generation
• Portfolio effects

Let's break them down. We will start by giving some benchmarks across several different matching timescales, but for the remainder of the article, we will focus on hourly matching scores, given that this is probably why you are here!

What temporal granularity are you looking at?

The timescale over which you measure your matching score is the biggest single factor that can affect it. Remember how our oat-milk-loving friend in our previous post went from having 100% of their oat milk needs met to only 20% when we looked at the daily picture of oat milk availability instead of the weekly view? The same thing happens with clean electricity consumption. Matching scores tend to decrease as we look at the clean electricity picture in greater and greater detail, but the threshold for what is considered a “good” matching score also decreases. A matching score lower than 100% is mediocre when viewed in the annual context, but when examining the hourly picture, even achieving 80% matched is an impressive feat on most grids. The table below provides a concise summary of what may be considered a good matching score, depending on the level of detail at which we are looking at the matching. Bear in mind that these categories can be quite fluid, and that other factors, such as your purchased generation mix, also impact your matching score.

Table 1: Matching score variation by granularity

*Some corporates over-procure clean energy to burnish their green credentials. These are often large tech companies, such as Google or Microsoft that buy more green energy than they consume over the year to improve their hourly matching scores.

What technologies are you using?

The type of renewable technology used, and its associated profile, have of course a strong impact on the overall matching score. Here are the most common technologies and how they stack up matching-score-wise:

Solar power generates exclusively during daylight hours, with peak production around midday. However, solar cannot provide any matching for evening or overnight demand, and seasonal variations mean significantly less generation during winter months. As a rule of thumb, you can expect pure solar generation to provide 30-55% matching.

Wind power has more variability. Wind patterns differ by location and season, but wind generally provides more consistent generation across day and night compared to solar. However, wind is highly dependent on weather conditions and can experience long periods of low generation during calm weather. Pure wind generation generally performs a little better than solar, however, usually ranging between 40% and 65% matching for the best performing offshore wind plants.

Hydroelectric power varies significantly depending on the type of installation. Run-of-river hydro provides relatively consistent baseload generation, while reservoir-based hydro can be dispatched more flexibly to match demand patterns, but this is only valuable if the dispatch is well-matched with your own business’ consumption. Baseload hydro provided by run-of-the-river plants can provide similar matching scores to nuclear or geothermal energy, but dispatchable reservoir-based hydro’s matching scores vary much more and are heavily dependent on the dispatch pattern.

Nuclear power, while carbon-free, typically operates as consistent baseload (flat) generation and offers limited flexibility for matching variable demand patterns. However, its high capacity factor generally means that it can still provide high matching scores in the 75%-95% range.

Geothermal power is a more niche technology, and is relatively rare outside of geologically active regions such as Iceland, Italy, or Kenya (although there are startups such as Fervo Energy are working to make it viable outside those regions). These plants provide high-quality baseload renewable power, similar to nuclear, so you can expect matching scores between 75% and 95% if you were powered by geothermal plants.

Batteries are an unusual form of generation in that they rely on first being charged by another renewable energy technology. However, when paired with an intermittent source of generation, such as wind or solar power, they can effectively shift surplus energy to times of shortage, making them a valuable tool for improving matching scores.

Biogas and biomass can typically be dispatched on demand, but are also capable of baseload generation. This makes them very flexible, and these sources can therefore yield very high matching scores if well managed, often hitting 80% or more.

How many different technologies are you using?

In terms of the diversity of technologies used, the rule of thumb is that the more different types of technology used, the better. For example, while solar by itself does not provide a great matching score, often sitting below 40%, pairing it with some wind generation can quickly increase the matching score beyond the 65% mark, with scores above 70% achievable under the right circumstances. You can use the table below to get an impression of the scores you could expect depending on the number of technologies used, but this of course depends which technologies are used as well. A portfolio with just 2 technologies, such as baseload geothermal energy complemented by some dispatchable hydro, could hit 100% matching, but this is sadly quite an uncommon mix.

Table 2: Indicative matching scores by number of technologies

How well-aligned is your demand with clean generation?

The shape of your business’ demand also has a big impact on your matching score: if your business’ demand profile aligns naturally with readily available renewable sources, it can add a few extra percentage points to your business’ final matching score. For instance, if your business has offices located in a hot climate, a solar farm’s production is likely to be well-correlated with your own air-conditioning demand. Keeping your business’ consumption pattern in mind when selecting your energy product can therefore be an easy way of picking up a few extra points of matching score, and therefore reducing your emissions!

Is your business taking advantage of portfolio effects?

Whether or not your business’ demand is matched with clean energy as part of a larger portfolio of demand can have a huge impact on your matching score. The mechanics of how this works are a little complicated, so we will cover this in more depth in a future post. The main thing you need to remember is this: if your business is part of a large and diverse pool of demand, and has access to a large and diverse pool of supply, your energy supplier will have more flexibility to match each consumer with the most appropriate supply from the pool. This is similar to how modern investors use diversified portfolios to reduce risks and improve returns: the more different stocks you are invested in, the less likely you are to go bankrupt if a single one of those companies failed. In the case of hourly matching, having lots of consumers and lots of supply makes it much more likely that in any given hour, even if your own consumption varies wildly, there will still be enough generation to cover for those variations. This can increase business’ matching scores by up to 10-15% in the best cases.

To summarise:

• Generally matching scores decrease when the level of detail increases: scores of 100% matching are typical at an annual level, scores between 80% and 95% would be typical at a monthly level, and between 40% and 80% would be in the normal range for hourly matching.
• The type of technology used influences your matching score: intermittent sources such as wind and solar tend to offer lower matching scores (30-55% for solar, 40-65% for wind), whereas baseload or dispatchable sources such as nuclear, geothermal, biogas/biomass or hydro can yield better scores (75%-95%).
• Technology diversity is your friend when it comes to hourly matching! The more different technologies used, the better (in most cases).
• You should keep the shape of your business’ demand in mind when choosing your energy products: try to pick technologies/products that naturally work well with your business’ demand profile.
• Signing up to a product where your business’ consumption is matched alongside many other business’ may feel less “premium”, but it can have a large positive impact on your matching score.

Further reading

If you are interested to see how some matching score tiers have been formalised in sustainability standards, check out the UK Green Buildings Council’s standard for what constitutes the gold standard of UK clean electricity procurement!