Energy Tariff Comparison
Two electricity or gas offers compared on your consumption, with the point where the other one wins and whether off-peak pays.
Runs entirely in your browser. Nothing is uploaded, logged or stored.
Difference over a year
12.00 cheaper with the second offer
- First offer, over a year
- 1,680.00
- Second offer, over a year
- 1,668.00
- Second offer: average price per kWh at your share
- 0.2460
- The two cost the same at
- 3,000 kWh a year
- Off-peak share at which the two cost the same
- 36.7 %
Put two offers side by side — your current one and the one you are looking at, or the same supplier with and without an off-peak option — with your yearly consumption, and this says which costs less over a year, by how much, and at what point the other one would win instead.
How it works
Each offer costs its price per kilowatt-hour times your consumption, plus its fixed charge over a year. A fixed charge quoted per day is counted over 365.25 days, one per month over twelve.
An offer with two prices is averaged by your share at each: at 40 % off-peak, a kilowatt-hour costs 40 % of the off-peak price plus 60 % of the peak one.
Because both costs grow in a straight line with consumption, the two lines cross at most once. That crossing is the consumption at which the two offers cost the same: below it one wins, above it the other. The same reasoning gives the off-peak share at which a two-rate offer starts to pay.
Examples
| Case | Input | Result |
|---|---|---|
| One price against two | 6,000 kWh; 0.25 + 15 a month; 0.27 and 0.21 at 40 % off-peak + 16 a month | 1,680.00 against 1,668.00 — 12.00 cheaper with the second offer |
| Where the verdict turns | The same two offers | Same cost at 3,000 kWh a year, and at 36.7 % off-peak |
Frequently asked questions
Why does it not list the suppliers' offers?
Because they differ by country, by region and by month, and a list kept here would be out of date or invented. The figures are on your bill and on the supplier's price list, and that is all the comparison needs.
How do I know my off-peak share?
If you already have a two-rate meter, your bill gives the consumption at each rate: divide the off-peak figure by the total. If not, the break-even share tells you how much of your consumption you would need to move to off-peak hours for the option to pay.
Does it work for gas?
Yes — the arithmetic is the same for any energy sold by the kilowatt-hour with a fixed charge. Leave the off-peak price empty for an offer with a single price.
Good to know
- The figures the page opens on are an example, not anybody's tariff. Taxes and levies charged per kilowatt-hour belong in the price; those charged per month or per year belong in the fixed charge.