How to Run Your First Tariff Comparison

A comparison is the whole point of Heat Pump Tariffs. It takes every tariff available in your region, applies each one's rates to your actual half-hourly electricity usage, and tells you what each would have cost — so you can see, in pounds, which tariff is genuinely cheapest for the way you use power. Not a headline rate, not a national average: your real bill, on every tariff, side by side.

If you've just uploaded your readings, you may already have been dropped straight into one. This guide walks through running a comparison from scratch and, more importantly, making sense of what comes back.

Before you start: two prerequisites

A comparison needs two things in place:

1. Your DNO region must be set. This tells the site which region's prices to use. If it isn't set, you'll be sent to your profile to choose it before you can continue — it's required, not optional.
2. You need some meter readings in. The more days of data you have, the more accurate the result. A comparison run against three days of data is far less reliable than one run against a full month.

If both are sorted, you're ready.

What a comparison actually does

In plain terms: for each tariff, the site walks through your half-hourly usage and charges every half-hour at that tariff's rate, adds the daily standing charges, and totals it up. For a flat-rate tariff that's straightforward. For Economy 7 or time-of-use tariffs it matters when you used electricity — cheap overnight units cost less than expensive evening ones — which is exactly why comparing against your real usage pattern beats any estimate.

The result is a like-for-like cost for every tariff over the same period, ranked cheapest to most expensive.

How to run one

1. Go to the Compare page.
2. Choose a date range. You'll see a set of range cards — All Data, Last 365 Days, Last 12 Months, By Year, By Month, and Recent. For a first run, pick a range you have good coverage for. A full recent month is a great starting point: long enough to be representative, recent enough to reflect current habits.
3. Decide on projection. If you pick a range shorter than a year, you'll see a Project to full year (365 days) toggle. Turning it on scales the costs up to an annual figure, which makes tariffs easier to compare and matches how suppliers usually quote. Leaving it off shows the cost for just the period you selected.
4. Include your current tariff if you've set one, so the site can show how much you'd save (or lose) by switching. If you haven't set a current tariff, the comparison still ranks everything — you just won't get a personal "you could save £X" figure.
5. Choose which tariffs to compare — by default you can compare against the full field for your region.
6. Click Run Comparison.

Most comparisons finish in a few seconds. A large one — lots of tariffs over a long period — may run in the background instead; if so, you'll see a progress banner and the results will appear when it's done. You don't need to wait on the page.

Reading the results

The results come back as a ranked table, cheapest at the top. Here's what to look at:

• The ranking and total cost. Each row shows a tariff and its total projected cost over your chosen period (scaled to a full year if you turned projection on). The cheapest sits at the top.
• The best deal. The top-ranked tariff is highlighted as the standout — the cheapest option for your usage in your region.
• Your current tariff. If you included it, it's marked in the table so you can see exactly where you stand and how much moving to the best deal would save you.
• Savings. Where shown, the savings figure is the difference between your current tariff's cost and a cheaper option's, over the same period — a real number based on your usage, not a marketing estimate.

Worked example

Suppose you select Last Month, leave projection on, and include your current standard tariff. The comparison runs, and the table comes back with a time-of-use tariff at the top showing an annual projected cost noticeably below your current flat-rate deal — because a chunk of your heat pump and EV charging happens overnight, where that tariff is cheap. Your current tariff sits a few rows down, with a savings figure next to the leader showing what you'd save by switching. That gap is the insight the whole exercise exists to surface.

Common mistakes

• Comparing with thin coverage. If your selected period has missing or partial days, your usage is understated — which flatters every tariff equally and muddies the ranking. Check your coverage on the readings page first; a range with full coverage gives a trustworthy result.
• Reading too short a period. Three days of data isn't representative of a year. Heat pump usage especially swings with the weather, so a single cold snap or mild week can skew a short comparison. Prefer a full month or more for your first run.
• Confusing cheapest headline rate with cheapest for you. A tariff with the lowest unit rate isn't automatically your cheapest — standing charges, time-of-use bands and when you use power all factor in. That's the entire reason to compare against your own data rather than picking by the advertised rate.
• Expecting a custom tariff to appear that you didn't save. If you wanted to compare against a specific deal that isn't in the database, you need to add it as a custom tariff first — otherwise it won't be in the field.
• Wrong region. If your DNO region is set incorrectly, every price is for somewhere else. If the results look strange, double-check your region matches the two-digit code on your MPAN.

Once you've run your first comparison, you can run as many as you like — different periods, different tariff selections — and the site keeps a history so you can revisit past results. From here, the natural next step is to set up automatic comparisons so you're alerted when a better deal appears, without having to check manually.